solved exercises

Entrepreneurship – Class 9 Solved Exercises | Complete Guide

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MCQs

1. What is entrepreneurship?

a) The process of starting a new business or organization ✅
b) The process of buying and selling stocks
c) The process of working for a large company
d) The process of creating a marketing campaign

Answer: a
Explanation: Entrepreneurship refers to the act of identifying business opportunities, taking risks, and creating new businesses or organizations.

💡 Tip: Entrepreneurs often innovate and take risks to bring new ideas to life.

2. What is a key characteristic of entrepreneurs?

a) Avoiding risks
b) Seeking job security
c) Innovation ✅
d) Following established methods

Answer: c
Explanation: Entrepreneurs are known for their ability to innovate, find creative solutions, and introduce new products or services.

💡 Tip: Successful entrepreneurs embrace change and think outside the box.

3. What is an example of a digital technology used by modern entrepreneurs?

a) Newspaper advertisements
b) Television commercials
c) Mobile apps ✅
d) Door-to-door sales

Answer: c
Explanation: Modern entrepreneurs use digital tools like mobile apps to reach customers, streamline operations, and enhance user experience.

💡 Tip: Digital technology helps businesses scale and reach a global audience quickly.

4. Which of the following is an example of a digital tool for creating and editing documents online?

a) SurveyMonkey
b) Google Docs ✅
c) SEMrush
d) Zendesk

Answer: b
Explanation: Google Docs allows users to create, edit, and collaborate on documents in real time using cloud technology.

💡 Tip: Use cloud-based tools like Google Docs for teamwork and remote work efficiency.

5. Which tool is commonly used for optimizing website content for search engines?

a) Hootsuite
b) Yoast SEO ✅
c) Shopify
d) PayPal

Answer: b
Explanation: Yoast SEO is a popular plugin for optimizing website content to rank higher on search engines like Google.

💡 Tip: SEO (Search Engine Optimization) helps businesses increase online visibility and attract more customers.

6. Which of the following is NOT a technique for identifying market needs?

a) Surveys and Questionnaires
b) Market Research
c) Observation
d) Brainstorming ✅

Answer: d
Explanation: Brainstorming is a creative process for generating ideas, but it is not a direct technique for identifying market needs.

💡 Tip: Use surveys, research, and observation to gather real customer insights before launching a product.

7. What is the first step in the design thinking process?

a) Prototyping
b) Testing
c) Empathizing ✅
d) Defining

Answer: c
Explanation: The design thinking process begins with “Empathizing,” which involves understanding the users’ needs and challenges.

💡 Tip: Always put yourself in the customer’s shoes to create user-friendly solutions.

8. What is the primary purpose of creating a business plan?

a) To attract investors
b) To outline strategies for growth ✅
c) To study market trends
d) To implement digital marketing strategies

Answer: b
Explanation: A business plan serves as a roadmap for a company’s goals, strategies, and operations, helping it grow and succeed.

💡 Tip: A well-structured business plan increases the chances of securing funding and achieving long-term success.

9. What does market analysis involve?

a) Calculating revenue forecasts
b) Researching competitors and understanding customer needs ✅
c) Developing pricing strategies
d) Implementing digital marketing campaigns

Answer: b
Explanation: Market analysis helps businesses understand their target audience, competition, and market trends for better decision-making.

💡 Tip: Conduct thorough market research before launching a product to increase its chances of success.

10. Which Sustainable Development Goal (SDG) focuses on affordable and clean energy?

a) SDG5
b) SDG7 ✅
c) SDG12
d) SDG17

Answer: b
Explanation: SDG7 aims to ensure access to affordable, reliable, sustainable, and modern energy for all.

💡 Tip: Sustainable businesses contribute to global development by adopting clean and renewable energy sources.

Short Questions with Answers

1. What is the meaning of the word entrepreneur and its origin?

Answer: The word entrepreneur means a person who starts and runs a business. It comes from the French word entreprendre, which means “to undertake” or “to start something new.”

Keywords: Entrepreneur, business, undertake, French origin.

2. How do digital technologies help entrepreneurs reach a global audience?

Answer: Digital technologies like websites, social media, and online ads help businesses connect with people worldwide. They allow entrepreneurs to sell products online and communicate with customers easily.

Keywords: Digital technologies, websites, social media, global audience, online ads.

3. What is an e-commerce platform, and why is it important for businesses?

Answer: An e-commerce platform is a website or app where businesses sell products online. It is important because it helps businesses reach more customers, operate 24/7, and reduce costs.

Example: Daraz.pk is a popular e-commerce platform in Pakistan.

Keywords: E-commerce, online shopping, business, customers, Daraz.pk.

4. Why is it important to identify market needs when generating a business idea?

Answer: Understanding market needs helps businesses create products that people want. This increases the chances of success and profits.

Example: If people need affordable mobile accessories, starting a budget-friendly accessories shop will be a good idea.

Keywords: Market needs, business idea, success, customer demand, profit.

5. What is the main purpose of using design thinking in creative problem-solving?

Answer: Design thinking helps businesses find innovative and user-friendly solutions. It focuses on understanding customer problems and creating better products or services.

Keywords: Design thinking, problem-solving, innovation, customer needs, creativity.

6. Explain the importance of market analysis in a business plan. Give an example relevant to a local business in Pakistan.

Answer: Market analysis helps businesses understand their customers, competitors, and trends. This allows them to make better decisions.

Example: A local bakery in Pakistan can study what types of cakes are most popular before opening a new shop.

Keywords: Market analysis, business plan, customers, competitors, bakery.

7. What are revenue models, and why are they essential components of a business plan?

Answer: A revenue model is how a business earns money. It is important because it helps businesses plan their income and growth.

Example: A business can sell products, offer subscriptions, or charge service fees to make money.

Keywords: Revenue model, business plan, income, growth, subscriptions.

8. How can businesses contribute to environmental sustainability according to the Sustainable Development Goals?

Answer: Businesses can help the environment by using eco-friendly materials, reducing waste, and saving energy. This supports the Sustainable Development Goals (SDGs) for a cleaner planet.

Example: A company in Pakistan can use biodegradable packaging instead of plastic to reduce pollution.

Keywords: Sustainability, environment, SDGs, biodegradable, waste reduction.

Long Questions with Answers

1. Importance of Entrepreneurship for Economic Growth and Innovation

Answer:

Entrepreneurship plays a key role in economic growth and innovation by creating new businesses, jobs, and solutions to everyday problems. Entrepreneurs bring new ideas that improve industries and contribute to a country’s development.

How Entrepreneurship Supports Economic Growth:

  1. Job Creation: Entrepreneurs start businesses, which provide employment opportunities.
    • Example: Startups like Careem in Pakistan created thousands of jobs.
  2. Encourages Investment: New businesses attract local and foreign investors, boosting the economy.
  3. Increases Competition: More businesses mean better products and services for customers.
  4. Contributes to GDP: Business activities add to a country’s Gross Domestic Product (GDP), strengthening the economy.

How Entrepreneurship Promotes Innovation:

  1. New Technologies: Entrepreneurs develop modern solutions using technology.
    • Example: Bykea, a Pakistani ride-hailing app, helps people travel and deliver parcels efficiently.
  2. Better Customer Solutions: Entrepreneurs focus on customer needs to improve existing products.
  3. Encourages Research and Development (R&D): Businesses invest in new ideas to stay competitive.

Keywords: Entrepreneurship, economic growth, innovation, job creation, GDP, investment, competition, research and development.

2. Market Research Tools, Online Marketing Tools, and E-commerce Platforms

Answer:

In the digital world, businesses need to analyze market trends, promote their products, and sell online to succeed.

1. Market Research Tools:

Market research helps businesses understand customer preferences, competitors, and demand.

  • Example: A business can use Google Trends to check which products are popular.
  • Survey Tools: Online forms like Google Forms help collect customer feedback.

2. Online Marketing Tools:

Businesses use social media and ads to reach more people.

  • Facebook Ads & Instagram Marketing: Help businesses target customers based on their interests.
  • SEO (Search Engine Optimization): Improves website ranking so people can find a business easily on Google.

3. E-commerce Platforms:

Online stores allow businesses to sell products globally.

  • Example: Daraz.pk and Shopify help businesses list products, receive orders, and accept payments.

How They Work Together:

  • A business researches market trends to find popular products.
  • It uses online marketing tools to advertise products on Facebook and Instagram.
  • Customers buy products from an e-commerce website, making the business successful.

Keywords: Market research, online marketing, SEO, e-commerce, customer targeting, social media advertising.

3. Design Thinking Process and Application in Rural Pakistan

Answer:

The design thinking process is a creative way to solve problems and develop new products or services.

Five Stages of Design Thinking:

  1. Empathize – Understand the customer’s problems.
  2. Define – Clearly identify the problem.
  3. Ideate – Brainstorm possible solutions.
  4. Prototype – Create a sample product.
  5. Test – Check if the solution works and improve it.

Example: Helping Farmers in Rural Pakistan

Problem: Many farmers in rural Pakistan struggle with low crop production due to lack of modern techniques.

Applying Design Thinking:

  • Empathize: Talk to farmers to understand their problems.
  • Define: The main issue is the lack of access to real-time weather and market prices.
  • Ideate: Develop a mobile app that provides weather updates, crop prices, and farming tips.
  • Prototype: Create a simple version of the app and test it with local farmers.
  • Test: Farmers use the app and provide feedback for improvements.

Keywords: Design thinking, problem-solving, empathize, prototype, test, farmers, rural development.

4. Business Plan for an Online Bookstore in Pakistan

Answer:

An online bookstore for students needs a clear plan for market research, revenue generation, and promotion.

(a) Market Analysis:

  • Target Audience: Students who need affordable textbooks and study guides.
  • Competitors: Liberty Books, Readings, Daraz Book Section.
  • Market Trend: Many students prefer ordering books online for convenience.

(b) Revenue Model:

  1. Direct Sales: Sell textbooks and storybooks through an online store.
  2. Subscription Model: Offer monthly book packages.
  3. Affiliate Marketing: Partner with publishers and earn commission.

(c) Digital Marketing Strategies:

  1. Social Media Ads: Promote books on Facebook, Instagram, and TikTok.
  2. SEO Optimization: Use keywords like “buy textbooks in Pakistan” for Google ranking.
  3. Discount Offers: Provide discounts for first-time buyers.

Keywords: Business plan, online bookstore, market analysis, revenue model, digital marketing, social media advertising, SEO.

5. Sustainable Development Goals (SDGs) & A Local Business in Pakistan

Answer:

The Sustainable Development Goals (SDGs) are 17 global goals to improve society, the environment, and the economy.

Example: Organic Farming Business in Pakistan

  • Business: A farm that grows organic vegetables without harmful chemicals.
  • Aligned SDGs:
    1. Good Health and Well-being (SDG 3) – Produces chemical-free food.
    2. Responsible Consumption and Production (SDG 12) – Reduces pesticide use and promotes eco-friendly farming.
    3. Decent Work and Economic Growth (SDG 8) – Provides jobs to local farmers.

Impact:

  • Social Impact: Promotes a healthy lifestyle and provides fair wages to farmers.
  • Environmental Impact: Reduces pollution by avoiding synthetic chemicals.
  • Economic Impact: Helps local farmers earn more by selling organic food at premium prices.

Keywords: SDGs, organic farming, sustainable business, environmental impact, economic growth, responsible consumption.

Emerging Technologies in Computer Science – 9th Class Solved Exercises

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Explore the latest emerging technologies in computer science with solved exercises for 9th-class students. Learn about AI, IoT, and more in a simple and easy way.

MCQS

1. Which of the following is not a subfield of AI?

a) Machine Learning
b) Natural Language Processing
c) Computer Vision
d) Robotics

✅ Answer: None of these (All are subfields of AI)

Explanation: Machine Learning, Natural Language Processing, Computer Vision, and Robotics are all subfields of Artificial Intelligence (AI). AI encompasses a variety of disciplines that enable machines to perform human-like tasks.

💡 Tip: Remember that AI is a broad field, and many subfields contribute to its overall development.

2. Which of these AI algorithms is considered an “explainable” model?

a) Neural Networks
b) Decision Trees
c) Random Forests
d) Convolutional Neural Networks

✅ Answer: b) Decision Trees

Explanation: Decision trees are considered explainable models because their decision-making process can be easily visualized and interpreted. Other models like Neural Networks and Convolutional Neural Networks (CNNs) are often considered “black-box” models due to their complexity.

💡 Tip: Explainability is crucial in fields like healthcare and finance, where understanding why a model made a decision is important.

3. Which of these is a security concern in IoT deployments?

a) Device vulnerability
b) Data privacy
c) Lack of standardization
d) All of the above

✅ Answer: d) All of the above

Explanation: IoT security concerns include device vulnerabilities, data privacy risks, and lack of standardization. These issues can make IoT systems susceptible to hacking and data breaches.

💡 Tip: When working with IoT, always prioritize security by using encryption, authentication, and software updates.

4. Which of the following is an application of AI in healthcare?

a) Personalized drug development
b) Automated diagnosis
c) Remote patient monitoring
d) All of the above

✅ Answer: d) All of the above

Explanation: AI is transforming healthcare through personalized medicine, automated diagnosis, and remote monitoring of patients, improving efficiency and patient outcomes.

💡 Tip: AI applications in healthcare rely heavily on data, so ensuring data privacy and regulatory compliance is crucial.

5. What is the primary purpose of using AI techniques in machine learning models?

a) To improve accuracy
b) To enhance interpretability
c) To reduce computational complexity
d) All of the above

✅ Answer: d) All of the above

Explanation: AI techniques help improve model accuracy, enhance interpretability (in some cases), and optimize computational efficiency.

💡 Tip: Different AI models serve different purposes—some focus on accuracy, while others focus on explainability or efficiency.

6. What is the key difference between explainable (whitebox) and unexplainable (blackbox) AI models?

a) The complexity of the model
b) The ability to understand the decision-making process
c) The performance of the model
d) The training data used

✅ Answer: b) The ability to understand the decision-making process

Explanation: Explainable AI (white-box models) allows users to understand how decisions are made, while black-box models (e.g., deep learning) do not provide clear reasoning for their outputs.

💡 Tip: Use explainable AI when working in fields that require transparency, such as finance, law, and healthcare.

7. Which of the following is an application of IoT in the transportation domain?

a) Smart traffic management
b) Vehicle-to-Vehicle (V2V) communication
c) Predictive maintenance of vehicles
d) All of the above

✅ Answer: d) All of the above

Explanation: IoT enhances transportation through smart traffic systems, V2V communication, and predictive maintenance, improving safety and efficiency.

💡 Tip: The future of smart cities relies on IoT-enabled transportation systems.

8. Which of these is a potential impact of AI and IoT on the job market?

a) Job displacement due to automation
b) Increased demand for specialized skills
c) Transformation of job roles and responsibilities
d) All of the above

✅ Answer: d) All of the above

Explanation: AI and IoT may lead to job losses in some sectors but will also create new job opportunities that require specialized skills. Many traditional roles will evolve with technological advancements.

💡 Tip: Upskilling in AI and IoT-related fields can help workers stay relevant in the job market.

9. What is the key concern associated with algorithmic bias in AI-powered decision-making processes?

a) Lack of transparency
b) Perpetuation of existing societal biases
c) Reduced accuracy of the model
d) All of the above

✅ Answer: d) All of the above

Explanation: Algorithmic bias can result from biased data, leading to unfair decisions, lack of transparency, and reduced accuracy in certain scenarios.

💡 Tip: To reduce bias, use diverse and representative datasets and test AI models for fairness.

10. Which of the following is an ethical principle that should be considered in the development and deployment of AI and IoT technologies?

a) Transparency and accountability
b) Respect for privacy and data rights
c) Fairness and non-discrimination
d) All of the above

✅ Answer: d) All of the above

Explanation: Ethical AI and IoT development should prioritize transparency, privacy, and fairness to prevent misuse and harm.

💡 Tip: AI regulations and guidelines, such as GDPR and responsible AI frameworks, help ensure ethical deployment.

Short Questions

1. Define Artificial Intelligence (AI).

Answer: Artificial Intelligence (AI) is the technology that enables machines to think, learn, and make decisions like humans. It helps computers perform tasks such as recognizing speech, solving problems, and making predictions.

🔑 Key Words: AI, machines, think, learn, decisions

2. What is the historical context and evolution of AI?

Answer: AI started in the 1950s when scientists began creating programs that could play games and solve math problems. Over time, AI improved with new technologies like machine learning and deep learning, making it more powerful in areas such as robotics, healthcare, and self-driving cars.

🔑 Key Words: 1950s, machine learning, deep learning, robotics

3. Provide two examples of AI applications in healthcare.

Answer:

  1. Automated Diagnosis – AI helps doctors identify diseases like cancer by analyzing medical images.
  2. Personalized Medicine – AI suggests the best treatment for patients based on their health data.

🔑 Key Words: Diagnosis, medical images, personalized medicine, treatment

4. Explain the role of AI techniques in advancing machine learning models.

Answer: AI techniques improve machine learning models by helping them learn from data more efficiently. They make predictions more accurate, find patterns in data, and reduce errors in decision-making.

🔑 Key Words: AI techniques, learn, patterns, predictions, accuracy

5. Define the Internet of Things (IoT).

Answer: The Internet of Things (IoT) is a network of devices, such as smartwatches, cars, and home appliances, that are connected to the internet and can share data with each other.

🔑 Key Words: IoT, devices, network, internet, data sharing

6. Describe the significance of IoT in connecting devices and systems.

Answer: IoT allows devices to communicate and work together, making everyday life easier. For example, smart home systems can control lights, temperature, and security through a smartphone.

🔑 Key Words: IoT, communication, smart devices, automation

7. What are the potential risks associated with AI and IoT?

Answer:

  1. Privacy Issues – Personal data can be misused if not protected properly.
  2. Cybersecurity Threats – Hackers can attack IoT devices and AI systems.
  3. Job Loss – Automation may replace some jobs in the future.

🔑 Key Words: Privacy, cybersecurity, hacking, automation, job loss

8. Discuss the societal impact of AI and IoT on daily life.

Answer: AI and IoT make life more convenient by improving healthcare, transportation, and home automation. However, they also raise concerns about privacy, job security, and ethical issues.

🔑 Key Words: Convenience, healthcare, transportation, automation, privacy

9. Explain the concept of algorithmic bias.

Answer: Algorithmic bias happens when AI makes unfair decisions because it has been trained on biased or incomplete data. This can lead to discrimination in hiring, loans, or law enforcement.

🔑 Key Words: Bias, unfair decisions, discrimination, data

10. Outline the importance of ethical considerations in AI and IoT.

Answer: Ethical considerations in AI and IoT ensure fairness, transparency, and privacy. Developers must make sure these technologies do not harm people or violate their rights.

🔑 Key Words: Ethics, fairness, transparency, privacy, rights

Here are the answers to your long questions in simple and easy words for 9th-class students.

1. Applications of AI in Education

Artificial Intelligence (AI) is helping students and teachers in many ways. It makes learning easier and more fun. Some of its applications in education are:

  1. Smart Tutors: AI-powered tutors, like chatbots, help students by answering their questions and explaining difficult topics. For example, software like “Socratic” helps students with their homework.
  2. Personalized Learning: AI studies how a student learns and then gives lessons that match their speed and understanding. Platforms like “Khan Academy” use AI to suggest lessons based on student performance.
  3. Automated Grading: AI helps teachers check exams and assignments quickly, saving their time.
  4. Language Translation: AI-powered tools like Google Translate help students understand books and lessons in different languages.
  5. AI in Special Education: AI assists students with disabilities. For example, speech-to-text tools help students who have trouble writing.

AI makes education more interesting, helps teachers focus on teaching, and gives students a better learning experience.

2. Explainable (Whitebox) vs. Unexplainable (Blackbox) AI Models

AI models work in different ways. Some are easy to understand, while others are complex and difficult to explain.

  1. Explainable AI (Whitebox AI):
    • These AI models work in a clear and understandable way.
    • People can see how the AI makes decisions.
    • Example: A simple rule-based chatbot that answers questions using a set of rules.
  2. Unexplainable AI (Blackbox AI):
    • These models are complex, and their decision-making process is not easy to understand.
    • Even experts find it hard to explain how they work.
    • Example: AI used in facial recognition and deep learning systems.

Whitebox AI is safer and easier to trust because its decisions can be checked, while Blackbox AI is powerful but sometimes risky because its decisions are difficult to explain.

3. Components of an IoT System

The Internet of Things (IoT) is a network of smart devices that communicate over the internet. An IoT system has several components:

  1. Sensors: These devices collect information from the environment, like temperature, humidity, or motion. Example: A smart thermometer in a room.
  2. Connectivity: The sensors send data using Wi-Fi, Bluetooth, or mobile networks.
  3. Cloud Storage: The collected data is stored in cloud servers so that it can be processed.
  4. Processing Unit: AI and software analyze the data and make decisions. Example: A smart AC that turns on when it detects high temperature.
  5. User Interface: Users can control IoT devices using apps on their phones. Example: A mobile app to control smart lights at home.

These components work together to make smart homes, cities, and industries more efficient.

4. Applications of IoT in Transportation

IoT has made transportation faster, safer, and more efficient. Some applications include:

  1. Smart Traffic Lights: IoT-powered traffic lights adjust based on real-time traffic, reducing jams.
  2. Vehicle Tracking: GPS-based IoT systems help track buses, trucks, and delivery vehicles. Example: Apps like Uber track cars in real-time.
  3. Smart Parking: IoT sensors detect empty parking spots and guide drivers to them.
  4. Connected Cars: Modern cars use IoT to detect issues, suggest repairs, and improve fuel efficiency.

IoT is making transportation more advanced, reducing accidents, and saving time.

5. Privacy Concerns in IoT

IoT devices collect a lot of personal data, leading to privacy risks. Some concerns are:

  1. Data Hacking: Hackers can steal private information from smart devices.
  2. Unauthorized Access: If IoT devices are not secured, anyone can control them.
  3. Location Tracking: IoT systems track locations, which can be misused.

To reduce these risks, strong security measures like passwords and data encryption should be used.

6. Impact of AI and IoT on Jobs

AI and IoT are changing the way people work. Some positive and negative effects include:

  1. New Job Opportunities: AI and IoT create jobs in technology fields like software development and robotics.
  2. Automation of Tasks: AI replaces humans in repetitive tasks like data entry and manufacturing.
  3. Job Losses: Many workers may lose their jobs as machines take over manual work.
  4. Improved Work Environments: IoT helps manage offices and industries more efficiently.

While AI and IoT bring many benefits, they also require workers to learn new skills to stay employed.

7. Policy and Regulatory Frameworks for AI and IoT

Governments create policies to make AI and IoT safe and fair. Some key frameworks include:

  1. Data Protection Laws: These laws protect personal information from being misused. Example: The GDPR in Europe.
  2. AI Ethics Guidelines: Some governments provide rules to ensure AI is used fairly.
  3. IoT Security Standards: Companies must follow security rules to prevent hacking.

These policies help make AI and IoT safer for everyone.

8. Algorithmic Bias in AI

Algorithmic bias happens when AI makes unfair decisions. This happens because AI learns from human data, which may contain mistakes or biases.

Examples of AI Bias:

  1. AI in hiring may prefer men over women if it was trained on biased company data.
  2. AI in loan approval may deny loans to certain groups due to biased past records.

How to Reduce AI Bias?

  • Use diverse and unbiased data for training AI.
  • Regularly check AI decisions to remove unfair biases.
  • Make AI models transparent so errors can be detected easily.

9. Ethical Principles for AI and IoT

Developers and users should follow ethical guidelines for AI and IoT:

  1. Fairness: AI should treat all people equally without bias.
  2. Transparency: AI and IoT systems should be open about how they work.
  3. Privacy Protection: Personal data should be kept secure.
  4. Safety: AI and IoT should not harm humans.
  5. Accountability: Companies should be responsible for AI and IoT actions.

These guidelines ensure that AI and IoT are used responsibly for the benefit of society.

Data Science and Data Gathering – 9th Class New Syllabus Solved Exercise

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Explore the 9th class new syllabus solved exercises on data science and data gathering. Understand key concepts, definitions, and examples with easy explanations. Ideal for students preparing for exams!

MCQ 1

Statement: What is data?

Options:
a) Processed information
b) Raw facts gathered about things
c) A collection of numbers only
d) A list of observed events

Answer: b) Raw facts gathered about things

Explanation:
Data refers to raw, unprocessed facts that are collected about objects, events, or people. These facts can later be processed to generate meaningful information.

Tip & Trick:

  • Data is raw and unprocessed, while information is processed and meaningful.
  • Numbers, text, symbols, and images can all be data.

MCQ 2

Statement: Which of the following is an example of qualitative data?

Options:
a) Temperature readings in degrees Celsius
b) Number of students in a class
c) Favourite ice cream flavours
d) Test scores out of 100

Answer: c) Favourite ice cream flavours

Explanation:
Qualitative data describes attributes, characteristics, or categories. It is non-numerical and usually represents opinions, preferences, or labels (e.g., colours, names, or flavours).

Tip & Trick:

  • Qualitative = Quality (Descriptive)
  • Quantitative = Quantity (Numerical)

MCQ 3

Statement: What type of data involves distinct, separate values that are countable?

Options:
a) Nominal Data
b) Ordinal Data
c) Discrete Data
d) Continuous Data

Answer: c) Discrete Data

Explanation:
Discrete data consists of distinct and separate values that can be counted (e.g., number of students, number of books). It cannot be divided into smaller parts meaningfully.

Tip & Trick:

  • Discrete = Distinct (Fixed numbers like 1, 2, 3, …)
  • Continuous = Can be divided (e.g., height, weight, time)

MCQ 4

Statement: What is an example of continuous data?

Options:
a) Number of cars in a parking lot
b) Height of students in centimetres
c) Types of fruits
d) Shirt sizes (small, medium, large)

Answer: b) Height of students in centimetres

Explanation:
Continuous data can take any value within a range and can be measured with precision. Heights, weights, and temperatures are examples of continuous data.

Tip & Trick:

  • Continuous = Can be measured & has decimals
  • Example: A person’s height can be 165.5 cm or 170.2 cm

MCQ 5

Statement: What type of data is used to categorize items without implying any order?

Options:
a) Ordinal Data
b) Discrete Data
c) Nominal Data
d) Continuous Data

Answer: c) Nominal Data

Explanation:
Nominal data categorizes things without any ranking or order (e.g., gender, blood groups, eye colour). Unlike ordinal data, it does not indicate a sequence.

Tip & Trick:

  • Nominal = Names only, No order
  • Example: Car brands (Toyota, Honda, Ford)

MCQ 6

Statement: How can you organise data to make it easier to analyse?

Options:
a) By writing it in long paragraphs
b) By creating tables, charts, and graphs
c) By storing it in random files
d) By keeping it in a messy notebook

Answer: b) By creating tables, charts, and graphs

Explanation:
Organizing data visually in tables, graphs, or charts helps in analysis, making patterns and trends easier to understand.

Tip & Trick:

  • Use tables for structured data
  • Use graphs for trends and comparisons

MCQ 7

Statement: Which tool can be used to create surveys online?

Options:
a) Microsoft Word
b) Google Forms
c) Excel Spreadsheets
d) Adobe Photoshop

Answer: b) Google Forms

Explanation:
Google Forms is a free tool by Google that allows users to create surveys, quizzes, and forms for data collection. It provides easy-to-use templates and automatic response collection.

Tip & Trick:

  • Microsoft Word is for document creation.
  • Excel is for data analysis, not direct survey creation.
  • Adobe Photoshop is for image editing.

MCQ 8

Statement: What is the main purpose of data collection?

Options:
a) To create random numbers
b) To gather information to answer questions or make decisions
c) To delete old data
d) To format text documents

Answer: b) To gather information to answer questions or make decisions

Explanation:
Data collection helps in making informed decisions, conducting research, and solving problems by gathering relevant facts and figures.

Tip & Trick:

  • Data collection is the foundation of research, business analysis, and decision-making.

MCQ 9

Statement: What is the primary purpose of data visualization?

Options:
a) To generate random numbers
b) To convert text into data
c) To make data easier to understand by turning it into pictures
d) To hide complex data

Answer: c) To make data easier to understand by turning it into pictures

Explanation:
Data visualization transforms raw data into charts, graphs, and infographics, making it easier to identify patterns and trends.

Tip & Trick:

  • Examples: Bar charts, pie charts, histograms.
  • Data visualization = Simplifying data with visuals

MCQ 10

Statement: Which tool is specifically designed for creating detailed and interactive visualizations?

Options:
a) Microsoft Excel
b) Google Sheets
c) Tableau
d) PowerPoint

Answer: c) Tableau

Explanation:
Tableau is a powerful data visualization tool used for creating interactive and insightful dashboards and reports.

Tip & Trick:

  • Excel & Google Sheets offer charts but lack advanced interactivity.
  • PowerPoint is for presentations, not data analysis.

MCQ 11

Statement: What is the first step in the data science process?

Options:
a) Data Cleaning
b) Data Analysis
c) Data Collection
d) Understanding the problem

Answer: d) Understanding the problem

Explanation:
Before collecting or analyzing data, it is crucial to understand the problem to determine what data is needed and how it should be used.

Tip & Trick:

  • Know the goal first!
  • The next steps: Data Collection → Cleaning → Analysis → Interpretation.

MCQ 12

Statement: What does the ‘Volume’ characteristic of Big Data refer to?

Options:
a) The speed at which data is generated
b) The different forms data can take
c) The sheer amount of data being collected
d) The way data is processed

Answer: c) The sheer amount of data being collected

Explanation:
Big Data is characterized by Volume (large amounts of data), Velocity (fast processing), and Variety (different data types).

Tip & Trick:

  • Big Data = Too big for traditional processing!
  • Example: Social media data, online transactions.

MCQ 13

Statement: What is an outlier in a dataset?

Options:
a) The most frequent value
b) The average of all values
c) An unusual or extreme value that doesn’t fit the pattern
d) The middle value when all values are arranged in order

Answer: c) An unusual or extreme value that doesn’t fit the pattern

Explanation:
Outliers are data points that are significantly different from others in a dataset. They can result from errors or unique variations.

Tip & Trick:

  • Example: If most students score between 60-80 in a test, a score of 10 or 99 could be an outlier.
  • Identify outliers using box plots or standard deviation analysis.

MCQ 14

Statement: What does data encryption do?

Options:
a) It converts data into a code to prevent unauthorized access.
b) It makes data available to everyone online.
c) It automatically deletes old data.
d) It speeds up internet connection.

Answer: a) It converts data into a code to prevent unauthorized access.

Explanation:
Data encryption secures information by converting it into an unreadable format, which can only be decoded with a key or password.

Tip & Trick:

  • Encryption = Locking data with a key!
  • Common encryption methods: AES, RSA.

Q1: What is the difference between qualitative and quantitative data?

Answer:
Qualitative data describes qualities or characteristics, while quantitative data consists of numerical values that can be measured or counted.

Explanation:

  • Qualitative data includes categories, names, labels, or descriptions (e.g., eye color, favorite food).
  • Quantitative data includes numerical values (e.g., height, weight, test scores).

Key Words: Qualitative = Descriptive, Quantitative = Numerical

Q2: Give an example of continuous data and explain why it is considered continuous.

Answer:
Example: Height of students in a class (e.g., 165.5 cm, 172.3 cm).
It is considered continuous because it can take any value within a range and can be measured with decimal precision.

Explanation:
Continuous data can be broken down into smaller parts and still retain meaning (e.g., temperature, time, speed).

Key Words: Measured, Decimal values, Range

Q3: Which method would you use to collect opinions from a large group of people about a new school policy?

Answer:
An online survey using Google Forms or paper-based questionnaires.

Explanation:
Surveys and questionnaires are efficient methods for collecting responses from a large group quickly and analyzing trends.

Key Words: Survey, Questionnaire, Large group, Data collection

Q4: What type of data is the number of students in your class?

Answer:
Discrete data

Explanation:
The number of students is a whole number (e.g., 25, 30). It cannot take decimal values and is countable.

Key Words: Discrete, Whole numbers, Countable

Q5: Why is it important to organize data into tables or charts before analyzing it?

Answer:
Organizing data in tables or charts makes it easier to identify patterns, trends, and relationships.

Explanation:
Raw data can be confusing, but when structured in charts or tables, it allows for better comparison and decision-making.

Key Words: Visualization, Patterns, Trends, Comparison

Q6: What is one advantage of using online tools like Google Forms for collecting survey data?

Answer:
Google Forms allows for automatic data collection and easy analysis.

Explanation:
Responses are stored digitally, reducing errors and saving time in organizing and analyzing results.

Key Words: Automatic, Digital, Time-saving, Error-free

Q7: Why might you need to integrate data from different sources when working on a project?

Answer:
To get a complete and accurate picture by combining information from multiple perspectives.

Explanation:
Different sources may provide complementary details, ensuring better decision-making and reducing biases.

Key Words: Integration, Accuracy, Multiple sources, Complete data

Q8: Describe a scenario where discrete data might be more useful than continuous data.

Answer:
Example: Counting the number of books in a library.

Explanation:
Discrete data is used when values are fixed and countable (e.g., number of students, tickets sold). It does not require measurements with decimals.

Key Words: Countable, Whole numbers, Fixed values

Q9: Explain why data visualization is important. How does it help in understanding complex information?

Answer:
Data visualization simplifies complex data by presenting it in an easy-to-read format.

Explanation:
Charts, graphs, and infographics allow people to quickly identify trends, patterns, and outliers that may not be obvious in raw data.

Key Words: Visualization, Patterns, Trends, Simplification

Q10: Describe what a line graph is used for and provide an example of data that could be displayed using a line graph.

Answer:
A line graph is used to show trends over time.

Example:
Tracking monthly sales growth in a business.

Explanation:
A line graph helps visualize changes over time and is useful in analyzing trends, such as population growth or temperature variation.

Key Words: Trends, Time-based, Growth, Decline

Q11: Explain the use of scatter plots in visualizing continuous data. Provide an example of a situation where a scatter plot would be useful.

Answer:
A scatter plot is used to show the relationship between two numerical variables.

Example:
Comparing study time vs. exam scores to see if more study hours improve performance.

Explanation:
Scatter plots help identify correlations between variables, such as positive, negative, or no correlation.

Key Words: Correlation, Relationship, Two variables, Trend analysis

Long Questions

Q1: Explain the differences between qualitative and quantitative data. Provide examples of each type.

Answer:
Qualitative data describes characteristics or categories, while quantitative data consists of numbers that can be measured or counted.

Example:

  • Qualitative Data: Favorite color, type of pet, eye color.
  • Quantitative Data: Age, height, number of students in a class.

Key Words: Qualitative = Descriptive, Quantitative = Numerical, Measurable

Q2: Describe the process of conducting a survey to gather data about students’ favorite extracurricular activities.

Answer:

  1. Decide the purpose – To find out students’ favorite activities.
  2. Design the survey – Create questions (e.g., multiple choice, ranking).
  3. Distribute the survey – Use Google Forms or paper forms.
  4. Collect responses – Gather data from students.
  5. Analyze results – Use tables or graphs to understand trends.

Key Words: Survey, Data Collection, Questionnaire, Analysis

Q3: Compare and contrast continuous and discrete data. Use examples in a school setting.

Answer:

  • Continuous Data: Can take any value within a range. Example: Students’ heights in cm (e.g., 155.3 cm, 160.5 cm).
  • Discrete Data: Only specific whole values. Example: Number of students in a class (e.g., 25, 30).

Comparison:

  • Continuous data is measured; discrete data is counted.
  • Continuous data can have decimal values; discrete data cannot.

Key Words: Measured, Counted, Whole Numbers, Decimal Values

Q4: Analyze the benefits and challenges of using digital tools like Google Forms for data collection.

Answer:
Benefits:

  • Quick data collection.
  • Automatic analysis using graphs and charts.
  • Accessible from anywhere.

Challenges:

  • Requires internet access.
  • Not everyone may be comfortable using digital tools.

Key Words: Digital, Easy Analysis, Internet Access, Automated

Q5: Imagine you are organizing a school event. How would you collect data on student preferences?

Answer:

  1. Create a survey – Ask about preferred activities and refreshments.
  2. Distribute the survey – Use Google Forms or paper forms.
  3. Collect and analyze responses – Use tables or pie charts.
  4. Plan the event – Arrange activities and food based on the survey results.

Key Words: Survey, Preferences, Data Collection, Event Planning

Q6: Explain the role of tables and charts in data analysis. Provide an example.

Answer:
Tables and charts make data easy to understand by organizing information visually.

Example: A bar chart can show students’ grades in different subjects, making it easier to compare performance.

Key Words: Visualization, Easy Comparison, Tables, Charts, Graphs

Q7: Describe a situation where non-numeric data is essential. How would you collect, store, and analyze it?

Answer:
Situation: Collecting student feedback about school environment (e.g., “Do you feel safe at school?”).

Steps:

  1. Collect – Use open-ended survey questions.
  2. Store – Save responses in a document or spreadsheet.
  3. Analyze – Identify common themes (e.g., “many students feel safe”).

Key Words: Non-numeric, Feedback, Open-ended, Thematic Analysis

Q8: Explain data visualization. How does it help in understanding complex data?

Answer:
Data visualization converts numbers into graphs and charts, making trends and patterns easier to understand.

Examples:

  • Line Graph: Temperature changes over time.
  • Pie Chart: Favorite subjects among students.

Key Words: Graphs, Charts, Simplify Data, Trends, Patterns

Q9: Discuss the importance of data visualization for businesses and decision-makers.

Answer:
Data visualization helps businesses make better decisions by presenting information clearly.

Benefits:

  • Easy decision-making: Sales trends shown in bar charts help plan future sales.
  • Quick comparisons: Pie charts show customer preferences clearly.

Key Words: Business, Decision-Making, Trends, Easy Comparison

Q10: Differentiate between nominal, ordinal, discrete, and continuous data. Provide suitable visualizations for each.

Answer:

  1. Nominal Data (Categories, No Order)
    • Example: Types of pets (dog, cat, fish).
    • Best Visualization: Pie Chart (percentage of each pet type).
  2. Ordinal Data (Ordered Categories)
    • Example: Student rankings (1st, 2nd, 3rd).
    • Best Visualization: Bar Chart (students’ rankings).
  3. Discrete Data (Whole Numbers, Countable)
    • Example: Number of students in each class.
    • Best Visualization: Column Chart (class sizes).
  4. Continuous Data (Measurable, Decimal Values)
    • Example: Heights of students (e.g., 155.4 cm, 162.5 cm).
    • Best Visualization: Histogram (height distribution).

Key Words: Nominal = Categories, Ordinal = Order, Discrete = Countable, Continuous = Measurable

Chapter 5: Work, Energy, and Power – Solved Exercise for 9th Class Physics (New Syllabus)

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Learn Chapter 5: Work, Energy, and Power from the new Physics syllabus for 9th class. Explore solved exercises with detailed explanations and tips to excel in your exams.

Question 5.1

Statement: Work done is maximum when the angle between the force F and the displacement d is:
Options:
(a) 0∘
(b) 30∘
(c) 60∘
(d) 90∘

Answer: (a) 0∘

Explanation:
The work done is given by the formula: W=Fdcos⁡θ

The cosine function is maximum when θ=0∘ because cos⁡0∘=1. Thus, work done is maximum when the force and displacement are in the same direction.

Tip: Memorize that cos⁡θ decreases as the angle increases from 0∘ to 90∘. For θ=90∘, work done becomes zero.

Question 5.2

Statement: A joule can also be written as:
Options:
(a) kg m2s−2
(b) kg m s−1
(c) kg m−2s−2
(d) kg m s−2

Answer: (a) kg m2s−2

Explanation:
A joule is the unit of energy or work, given as: Work=Force×Displacement

Force is measured in kg m s−2, and displacement in meters . Therefore, Joule=(kg m s−2)×m=kg m2s−2.

Tip: Remember that joules involve mass, distance squared, and time squared in their derived units.

Question 5.3

Statement: The SI unit of power is:
Options:
(a) joule
(b) newton
(c) watt
(d) second

Answer: (c) watt

Explanation:
Power is the rate at which work is done or energy is transferred. It is defined as: P=W/t

Where P is power in watts, W is work in joules, and t is time in seconds.

Tip: Memorize key SI units: work (joule), force (newton), and power (watt).

Question 5.4

Statement: The power of a water pump is 2 kW. The amount of water it can raise in one minute to a height of 5 m is:
Options:
(a) 1000 litres
(b) 1200 litres
(c) 2000 litres
(d) 2400 litres

Answer: (d) 2400 litres

Explanation:
The power of the pump is P=2000 WP . Work is given by: W=mgh

Where mm is mass, g=9.8 m/s2, and h=5 m. Power is work done per second: P=mgh/t

Rearranging for mm: m=P⋅t/gh=2000×60/9.8×5=240 kg

Since 1 kg of water equals 1 litre, the answer is 2400 litres.

Tip: Always use consistent units and formulas for work, power, and time.

Question 5.5

Statement: A bullet of mass 0.05 kg has a speed of 300 m/s. Its kinetic energy will be:
Options:
(a) 2250 J
(b) 4500 J
(c) 1500 J
(d) 1125 J

Answer: (b) 4500 J

Explanation:
Kinetic energy is given by: KE=1/2mv2

Substitute m=0.05 kg and v=300 m/s

KE=1/2×0.05×(300)2=4500 J

Tip: Remember to square the velocity in the formula.

Question 5.6

Statement: If a car doubles its speed, its kinetic energy will be:
Options:
(a) the same
(b) increased four times
(c) increased two times
(d) reduced two times

Answer: (b) increased four times

Explanation:
Kinetic energy depends on the square of velocity: KE∝v2

If the speed doubles (v→2v), the kinetic energy becomes: KE∝(2v)2=4v2.

Tip: Always relate proportionality with squared terms in energy calculations.

Question 5.7

Statement: The energy possessed by a body by virtue of its position is:
Options:
(a) kinetic energy
(b) potential energy
(c) chemical energy
(d) solar energy

Answer: (b) potential energy

Explanation:
Potential energy is the energy stored in an object due to its position in a gravitational field, given by: PE=mgh

Tip: Potential energy depends on height, while kinetic energy depends on motion.

Question 5.8

Statement: The magnitude of momentum of an object is doubled; the kinetic energy of the object will:
Options:
(a) double
(b) increase to four times
(c) reduce to one-half
(d) remain the same

Answer: (b) increase to four times

Explanation:
Momentum (pp) is related to kinetic energy (KE) as:

KE=p2/2m

If momentum doubles (p→2p)

KE∝(2p)2=4p2

Tip: Understand the relationship between momentum and kinetic energy.

Question 5.9

Statement: Which of the following is not renewable energy?
Options:
(a) Hydro-electric energy
(b) Fossil fuels
(c) Wind energy
(d) Solar energy

Answer: (b) Fossil fuels

Explanation:
Fossil fuels (coal, oil, natural gas) take millions of years to form and are not renewable. Renewable energy sources like solar, wind, and hydro are replenished naturally.

Tip: Fossil fuels are non-renewable because their reserves are finite.

Here are the solutions to the short answer and constructed response questions with clear and simple explanations:

Short Answer Questions (Part B)

Question 5.1

What is the work done on an object that remains at rest when a force is applied to it?
Answer:
The work done is zero.
Explanation:
Work is given by the formula: W=F⋅d⋅cos⁡θ

Since the object remains at rest, the displacement d=0. Therefore, work W=0.

Question 5.2

A slow-moving car may have more kinetic energy than a fast-moving motorcycle. How is this possible?
Answer:
Kinetic energy depends on both mass and velocity: KE=1/2mv2

If the car is very heavy (large m) and the motorcycle is light (small m), the car’s kinetic energy can be greater even if it moves slowly.

Question 5.3

A force F1 does 5 J of work in 10 s. Another force F2 does 3 J of work in 5 s. Which force delivers greater power?
Answer:
Power is given by: P=W/t

For F1: P1=5/10=0.5 W

For F2: P2=3/5=0.6 W

Thus, F2 delivers greater power.

Question 5.4

A woman runs up a flight of stairs. The gain in her gravitational potential energy is 4500 J. If she runs up the stairs with twice the speed, what will be her gain in potential energy?
Answer:
The gain in potential energy will still be 4500 J.
Explanation:
Potential energy depends only on height (PE=mgh), not on speed. Running faster does not change the height.

Question 5.5

Define work and its SI unit.
Answer:
Work is done when a force moves an object in the direction of the force. Mathematically: W=F⋅d⋅cos⁡θ

The SI unit of work is the joule (J).

Question 5.6

What is the potential energy of a body of mass mm when it is raised through a height hh?
Answer:
Potential energy is given by: PE=mgh

Where:

  • m = mass of the body
  • g = gravitational acceleration (9.8 m/s2)
  • h = height

Question 5.7

Find an expression for the kinetic energy of a moving body.
Answer:
Kinetic energy is given by: KE=1/2mv2

Where:

  • m = mass of the body
  • v = velocity of the body

Question 5.8

Define the efficiency of a working system. Why can a system not have 100% efficiency?
Answer:
Efficiency is the ratio of useful energy output to the total energy input: Efficiency=Useful Energy Output/Total Energy Input ×100

No system can have 100%100\% efficiency because some energy is always lost as heat, sound, or friction.

Question 5.9

What is power? Define the unit used for it.
Answer:
Power is the rate at which work is done or energy is transferred: P=W/t

The SI unit of power is the watt (W).

Question 5.10

Differentiate between renewable and non-renewable energy sources.
Answer:

  • Renewable energy: Can be replenished naturally, e.g., solar, wind, and hydro energy.
  • Non-renewable energy: Exists in limited quantities and cannot be replenished, e.g., fossil fuels (coal, oil).

Constructed Response Questions (Part C)

Question 5.1

Can the kinetic energy of a body ever be negative?
Answer:
No, kinetic energy cannot be negative.
Explanation:
Kinetic energy is given by KE=1/2mv2. Since both mass (m) and the square of velocity (v2) are always positive, KE is always positive.

Question 5.2

Which one has the greater kinetic energy: an object traveling with a velocity vv or an object twice as heavy traveling with a velocity of v2\frac{v}{2}?
Answer:
Let the mass of the first object be mm, so KE1=1/2mv2
The second object has mass 2m and velocity v2

KE2=1/2(2m)(v2)/2=1/2(2m)⋅v2/4=mv2/4

Thus, KE1>KE2.

Question 5.3

A car is moving along a curved road at constant speed. Does its kinetic energy change?
Answer:
No, the kinetic energy does not change.
Explanation:
Kinetic energy depends on speed, not direction. Since the speed is constant, the kinetic energy remains the same.

Question 5.4

Comment on the statement: “An object has one joule of potential energy.”
Answer:
The statement means the object’s potential energy is equal to the work done in lifting it to a certain height where: PE=1 J.

Question 5.5

While driving on a motorway, the tyre of a vehicle sometimes bursts. What may be its cause?
Answer:
A tyre may burst due to:

  1. Overheating from friction.
  2. Excessive air pressure.
  3. Damage from sharp objects.

Question 5.6

While playing cricket, a ball smashes a windowpane. Describe the energy changes in this event.
Answer:

  • The ball has kinetic energy while in motion.
  • Upon impact, the ball transfers energy to the windowpane, causing it to break.
  • Some energy is lost as sound and heat.

Question 5.7

A man rows a boat upstream at rest with respect to the shore. Is he doing work?
Answer:
No, he is not doing work with respect to the shore because there is no displacement.

Question 5.8

A cyclist goes downhill from the top of a steep hill without pedaling and takes it to the top of the next hill. Draw a diagram of what happened.
Answer:
The cyclist’s gravitational potential energy at the top of the first hill converts to kinetic energy as he descends, then converts back to potential energy as he climbs the next hill. A diagram would show a curved path between two hills.

Chapter 4 Stoichiometry SLO based solved Exercise 9th class new syllabus

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Get comprehensive solutions for Chapter 4 Stoichiometry from the 9th Class New Syllabus. This SLO-based solved exercise is designed to help students master the concepts of stoichiometry effectively.

(i) How many atoms are present in one gram of H2O?

1 mole of H2O = 18 g and contains 6.022×1023 molecules.
1 molecule of H2O = 3 atoms (2 H + 1 O).

Thus,
Atoms in 1 gram of H2O: 6.022×1023/18×3≈10.02×1022

Correct answer: (a) 10.02×1022 atoms

(ii) Which is the correct formula of calcium phosphide?

The formula of calcium phosphide is based on the charges of Ca2+ and P3−. To balance charges, the formula is Ca3P2

Correct answer: (c) Ca3P2

(iii) How many atomic mass units (amu) are there in one gram?

1 amu = 1.66×10−24g.

Number of amu in 1 g=1/1.66×10−24≈6.022×1023

Correct answer: (b) 6.022×1023

(iv) Structural formula of 2-hexene is CH3−CH=CH−(CH2)2−CH3. What is its empirical formula?

The molecular formula of 2-hexene is C6H12
Empirical formula is obtained by dividing subscripts by their greatest common divisor (6). Empirical formula=CH2

Correct answer: (b) CH2

(v) How many moles are there in 25 g of H2SO4?

Molar mass of H2SO4 = 2+32+(4×16)=98 g/mol

Moles=Mass/Molar mass=25/98≈0.255 moles.

Correct answer: (c) 0.255 moles

(vi) A necklace has 6 g of diamonds in it. What are the number of carbon atoms in it?

Diamonds are made of carbon.
Molar mass of carbon = 12 g/mol.
Number of moles of carbon: Moles=6/12=0.5 moles

Number of carbon atoms: 0.5×6.022×1023≈3.01×1023

Correct answer: (d) 3.01×1023

(vii) What is the mass of Al in 204 g of aluminum oxide (Al2O3)?

Molar mass of Al2O3 = 2(27)+3(16)=102 g/mol
Mass fraction of Al: 2(27)/102=54/102=0.5294

Mass of Al in 204 g of Al2O3: 0.5294×204≈108 g

Correct answer: (d) 108 g

(viii) Which one of the following compounds will have the highest percentage by mass of nitrogen?

  • For CO(NH2)2(urea):
    Molar mass = 12+16+2(14)+4(1)=60
    Nitrogen mass = 28
    Percentage of N = 28/60×100=46.67%
  • For NH4NO3:
    Molar mass = 14+4+14+3(16)=80
    Nitrogen mass = 28.
    Percentage of N = 28/80×100=35%

Correct answer: (a) CO(NH2)2

(ix) When one mole of each of the following compounds is reacted with oxygen, which will produce the maximum amount of CO2?

The number of moles of CO2 depends on the number of carbon atoms in the compound. Among the given options:

  • Methane (CH4): Produces 1 mole of CO2.
  • Ethane (C2H6): Produces 2 moles of CO2.
  • Diamond (C): Produces 1 mole of CO2

Correct answer: (b) Ethane

(x) What mass of 95% Ca(OH)2 will be required to neutralize 50 cm3 of 0.5 M H2SO4?

  • Reaction: Ca(OH)2+H2SO4→CaSO4+2H2O
    1 mole of H2SO4 reacts with 1 mole of Ca(OH)2.
    Moles of H2SO4: 0.5×0.05=0.025 moles
    Mass of pure Ca(OH)2: 0.025×(40+2(16+1))=0.025×74=1.85 g.
  • Mass of 95% pure Ca(OH)2: 1.850.95≈1.95 g

Correct answer: (d) 1.95 g

2. Questions for Short Answers

i. Write down the chemical formula of barium nitride.
The chemical formula of barium nitride is Ba₃N₂.
Explanation: Barium (Ba) is an alkaline earth metal with a +2 oxidation state, and nitride (N) is a nonmetal with a -3 charge. To balance the charges, three barium ions combine with two nitride ions, forming Ba₃N₂.

ii. Find out the molecular formula of a compound whose empirical formula is CH₂O and its molar mass is 180.
Step 1: Calculate the molar mass of the empirical formula (CH₂O).
Molar mass of CH₂O = 12 (C) + 2(1) (H) + 16 (O) = 30 g/mol.

Step 2: Determine the ratio of the molecular formula to the empirical formula.
Ratio=Molar mass of compound / Molar mass of empirical formula=180/30=6.

Step 3: Multiply the empirical formula by the ratio.
Molecular formula = (CH2O)6=C6H12O6 = C₆H₁₂O₆.
The molecular formula of the compound is C₆H₁₂O₆ (glucose).

iii. How many molecules are present in 1.5 g H₂O?
Step 1: Calculate the molar mass of water (H₂O).
Molar mass = 2(1) + 16 = 18 g/mol.

Step 2: Find the number of moles in 1.5 g of H₂O.
Moles = Mass/Molar mass=1.5/18=0.0833 mol

Step 3: Calculate the number of molecules using Avogadro’s number (6.022×1023 molecules/mol)
Number of molecules = 0.0833×6.022×1023=5.02×1022
Thus, there are approximately 5.02×1022

iv. What is the difference between a mole and Avogadro’s number?

  • Mole: A mole is a unit in chemistry that represents a quantity of substance. One mole of any substance contains the same number of particles (atoms, molecules, or ions) as there are in 12 g of carbon-12.
  • Avogadro’s Number: Avogadro’s number is a constant that defines the number of particles in one mole of a substance. It is equal to 6.022×1023 particles/mol

Difference: The mole is a quantity (like a dozen), while Avogadro’s number provides the specific count of particles in one mole.

v. Write down the chemical equation for the given reaction.
Copper + Sulphuric acid → Copper sulphate + Sulphur dioxide + Water
Balanced chemical equation:
Cu+2H₂SO₄→CuSO₄+SO₂+2H₂O

3. Constructed Response Questions

i. Different compounds will never have the same molecular formula but can have the same empirical formula. Explain.

  • The empirical formula represents the simplest whole-number ratio of elements in a compound, whereas the molecular formula shows the exact number of atoms of each element in a molecule.
  • Example: Acetic acid (C₂H₄O₂) and glucose (C₆H₁₂O₆) have the same empirical formula (CH₂O), but their molecular formulas are different.
  • Explanation: Compounds with different molecular structures can share the same empirical formula because the molecular formula is a multiple of the empirical formula.

ii. Write down the chemical formulas of the following compounds.

  1. Calcium phosphate: Ca₃(PO₄)₂
  2. Aluminium nitride: AlN
  3. Sodium acetate: CH₃COONa
  4. Ammonium carbonate: (NH₄)₂CO₃
  5. Bismuth sulphate: Bi₂(SO₄)₃

iii. Why does Avogadro’s number have immense importance in chemistry?
Avogadro’s number (6.022×1023 is essential in chemistry because:

  • It establishes a connection between the microscopic (atoms/molecules) and macroscopic (grams/moles) scales.
  • It allows chemists to calculate the number of particles in a given mass of substance.
  • It is crucial for determining stoichiometric relationships in chemical reactions, enabling precise calculations for reactants and products.

iv. When 8.657 g of a compound were converted into elements, it gave 5.217 g of carbon, 0.962 g of hydrogen, and 2.478 g of oxygen. Calculate the percentage of each element present in this compound.
Step 1: Calculate the total mass of the compound.
Total mass = 5.217+0.962+2.478=8.657 g

Step 2: Calculate the percentage of each element.

  • Carbon: 5.2178.657×100=60.3%
  • Hydrogen: 0.9628.657×100=11.1%
  • Oxygen: 2.4788.657×100=28.6%

Thus, the percentages are:

  • Carbon: 60.3%
  • Hydrogen: 11.1%
  • Oxygen: 28.6%.

4. Descriptive Questions

i. Which conditions must be fulfilled before writing a chemical equation for a reaction?
To write a chemical equation, the following conditions must be fulfilled:

  1. Correct identification of reactants and products: Ensure the substances involved in the reaction are accurately identified.
  2. Balancing the equation: The equation must follow the law of conservation of mass, where the number of atoms for each element is the same on both sides.
  3. Physical states of substances: Indicate the physical states of reactants and products (solid (s), liquid (l), gas (g), or aqueous (aq)).
  4. Reaction conditions: Specify the conditions such as temperature, pressure, or the use of catalysts if required for the reaction.

ii. Explain the concepts of Avogadro’s number and mole.

  • Avogadro’s Number: Avogadro’s number (6.022×1023 is the number of particles (atoms, molecules, or ions) in one mole of a substance. It bridges the gap between the microscopic scale and the macroscopic scale.
  • Mole: A mole is a unit of measurement used in chemistry to represent 6.022×1023 particles of a substance. It is the amount of a substance that contains as many entities as there are atoms in 12 grams of carbon-12.

iii. How many grams of CO₂ will be produced when we react 10 g of CH₄ with excess of O₂ according to the following equation?
CH4+2O2→CO2+2H2OCH₄ + 2O₂ → CO₂ + 2H₂O

  1. Molar masses:
    • CH₄ = 16 g/mol
    • CO₂ = 44 g/mol
  2. Moles of CH₄:
    Moles = Mass/Molar mass=10/16=0.625 mol
  3. Moles of CO₂:
    From the equation, 1 mole of CH₄ produces 1 mole of CO₂.
    Moles of CO₂ = 0.625 mol.
  4. Mass of CO₂:
    Mass = Moles × Molar mass = 0.625×44=27.5 g

Answer: 27.5 g of CO₂ will be produced.

iv. How many moles of coal are needed to produce 10 moles of CO according to the following equation?
3C+O2+H2O→H2+3CO3C + O₂ + H₂O → H₂ + 3CO

From the equation, 3 moles of carbon (C) produce 3 moles of CO.
Thus, to produce 10 moles of CO: Moles of coal=103=3.33 moles.\text{Moles of coal} = \frac{10}{3} = 3.33 \, \text{moles}.

Answer: 3.33 moles of coal are needed.

v. How much SO₂ is needed in grams to produce 10 moles of sulphur?
2H2S+SO2→2H2O+3S

From the equation, 1 mole of SO₂ produces 1.5 moles of sulphur.
To produce 10 moles of sulphur: Moles of SO₂=10/1.5=6.67 moles

Molar mass of SO₂ = 32 (S) + 2(16) = 64 g/mol.
Mass = Moles × Molar mass = 6.67×64=426.88 g

Answer: 426.88 g of SO₂ are needed.

vi. How much ammonia is needed in grams to produce 1 kg of urea fertilizer?
2NH3+CO2→CO(NH2)2+H2O

  1. Molar masses:
    • NH₃ = 17 g/mol
    • CO(NH₂)₂ (urea) = 60 g/mol
  2. Moles of urea:
    Moles = Mass/Molar mass=1000/60=16.67 mol
  3. Moles of NH₃:
    From the equation, 2 moles of NH₃ produce 1 mole of urea.
    Moles of NH₃ = 16.67×2=33.34 mol.
  4. Mass of NH₃:
    Mass = Moles × Molar mass = 33.34×17=566.78 g

Answer: 566.78 g of ammonia is needed.

vii. Calculate the number of atoms in the following:

(a) 3 g of H₂:
Moles of H₂ = Mass/Molar mass=3/2=1.5 mol
Number of molecules = 1.5×6.022×1023=9.033×1023
Each molecule of H₂ contains 2 atoms, so:
Number of atoms = 9.033×1023×2=1.8066×1024
Number of molecules = 3.4×6.022×1023=2.0475×1024
Each molecule of N₂ contains 2 atoms, so:
Number of atoms = 2.0475×1024×2=4.095×1024
Molar mass of C₆H₁₂O₆ = 6(12)+12(1)+6(16)=180 g/mol
Number of molecules = 0.0556×6.022×1023=3.348×1022
Each molecule contains 6+12+6=246 + 12 + 6 = 24 atoms.
Number of atoms = 3.348×1022×24=8.035×1023

5. Investigative Questions

i. How many moles of water are needed for a single adult?
Volume of water per glass = 400 cm3
Density of water = 1 g/cm3
Mass of water = 400×8=3200 g

Molar mass of water = 18 g/mol.
Moles of water = Mass/Molar mass=3200/18=177.78 mol

Answer: 177.78 moles of water are needed.

ii. How many moles of SiO₂ are present in the glass?
Assuming the mass of glass is provided, moles = Mass of glass/Molar mass of SiO₂

where Molar mass of SiO₂=28+2(16)=60 g/mol

Exercise Solutions Atomic Structure – Chapter 2, 9th Punjab Board New Book (2025)

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The detailed, step-by-step solutions to Chapter 2, “Atomic Structure,” from the new Punjab Board 9th Class textbook (2025 edition) by Ahsan Publishers. Aligned with the SLO-based syllabus, this guide provides clear explanations, solved exercises, and conceptual insights tailored to help students excel in their studies. Perfect for students preparing for exams and teachers seeking comprehensive teaching material.

(i) How many electrons can be accommodated at the most in the third shell of the elements?

  • Options:
    (a) 8
    (b) 18
    (c) 10
    (d) 32
  • Answer: (b) 18
  • Explanation:
    The maximum number of electrons in any shell is determined by the formula 2n2, where n is the shell number. For the third shell = 2(9) = 18 Thus, the third shell can accommodate a maximum of 18 electrons.

(ii) What information was obtained from discharge tube experiments?

  • Options:
    (a) Structure of atom was discovered.
    (b) Neutrons and protons were discovered.
    (c) Electrons and protons were discovered.
    (d) Presence of nucleus in an atom was discovered.
  • Answer: (d) Presence of nucleus in an atom was discovered.
  • Explanation:
    Rutherford’s experiments using a discharge tube and his gold foil experiment showed that atoms have a small, dense, positively charged nucleus at their center. These discoveries laid the foundation for understanding atomic structure.

(iii) Why have isotopes not been shown in the periodic table?

  • Options:
    (a) Periodic table cannot accommodate a large number of isotopes of different elements.
    (b) Some of the isotopes are unstable and they give rise to different elements.
    (c) All the isotopes have the same atomic number; so there is no need to give them separate places.
    (d) Isotopes do not show periodic behavior.
  • Answer: (c) All the isotopes have the same atomic number; so there is no need to give them separate places.
  • Explanation:
    Isotopes of an element have the same number of protons but differ in the number of neutrons. Since the periodic table is based on atomic number, isotopes are not given separate places—they occupy the same position.

(iv) Which particle is present in a different number in the isotopes?

  • Options:
    (a) Electron
    (b) Neutron
    (c) Proton
    (d) Both neutron and electron
  • Answer: (b) Neutron
  • Explanation:
    Isotopes are variants of the same element that have the same number of protons and electrons but differ in the number of neutrons. This difference in neutron number affects their atomic mass but not their chemical properties.

(v) Predict the boiling point of heavy water (D2O).

  • Options:
    (a) 101.4°C
    (b) 98.2°C
    (c) 100°C
    (d) 105.4°C
  • Answer: (a) 101.4°C
  • Explanation:
    Heavy water (D2O) has deuterium atoms instead of regular hydrogen atoms. Because deuterium is heavier, heavy water has slightly stronger intermolecular forces, resulting in a higher boiling point (approximately 101.4°C) compared to normal water (100°C).

(vi) What will be the relative atomic mass of hydrogen given the abundances of its two isotopes, 99.9844% and 0.0156%?

  • Options:
    (a) 1.0078
    (b) 1.0784
    (c) 1.0800
    (d) 1.0700
  • Answer: (a) 1.0078
  • Explanation:
    The relative atomic mass is calculated using the formula: Relative atomic mass=(m1⋅f1)+(m2⋅f2) , m1=1.0078, f1=0.999844 m2=2.0140 f2=0.000156 : (1.0078⋅0.999844)+(2.0140⋅0.000156)≈1.0078

(vii) How is radiocarbon dating useful for archeologists?

  • Options:
    (a) It helps determine the age of organic matter.
    (b) It helps determine the composition of matter.
    (c) It helps determine the usefulness of matter.
    (d) It helps determine whether the matter is radioactive or not.
  • Answer: (a) It helps determine the age of organic matter.
  • Explanation:
    Radiocarbon dating is based on measuring the decay of carbon-14, a radioactive isotope, to determine the age of organic materials such as bones, wood, or fossils. This technique is widely used in archeology to estimate the age of artifacts.

(viii) What does keep the particles present in the nucleus intact?

  • Options:
    (a) Particles are held together by strong nuclear force.
    (b) Particles are held together by weak nuclear force.
    (c) Particles are held together by electrostatic force.
    (d) Particles are held together by dipolar force.
  • Answer: (a) Particles are held together by strong nuclear force.
  • Explanation:
    The strong nuclear force is the fundamental force that binds protons and neutrons in the nucleus, overcoming the electrostatic repulsion between positively charged protons. This force operates only at very short ranges.

(ix) How do electrons keep themselves away from the oppositely charged nucleus?

  • Options:
    (a) By keeping themselves stationary
    (b) By revolving around the nucleus
    (c) Due to their wave-like nature
    (d) A magnetic field around the nucleus keeps them away
  • Answer: (b) By revolving around the nucleus
  • Explanation:
    Electrons revolve around the nucleus due to the balance between the electrostatic attraction to the positively charged nucleus and the centrifugal force from their motion. This concept is based on Bohr’s atomic model.

(x) Rubidium consists of two isotopes 85 and 87 . The percent abundance of the light isotope is 72.2%. What is the percent abundance of the heavier isotope? Its atomic mass is 85.47.

  • Options:
    (a) 15%
    (b) 28%
    (c) 37%
    (d) 72%
  • Answer: (b) 28%
  • Explanation:
    The percent abundances of isotopes must add up to 100%. Given that the light isotope has an abundance of 72.2%, the heavier isotope will have: 100%−72.2%=28%100

2. Questions for Short Answers

(i) Why is it said that almost all the mass of an atom is concentrated in its nucleus?
The nucleus of an atom contains protons and neutrons, which are much heavier than electrons. Since electrons are very light and located outside the nucleus, nearly all the mass of an atom comes from the protons and neutrons in its nucleus.

(ii) Why are elements different from one another?
Elements are different because they have different numbers of protons in their nuclei. The number of protons (also called the atomic number) is unique to each element and determines its properties and behavior.

(iii) How many neutrons are present in 83Bi 210
The isotope Bi 210 has a mass number (number of protons and number of neutrons) of 210 and an atomic number (number of protons) of 83. Number of neutrons=Mass number−Atomic number=209−83=126

So, it has 126 neutrons.

(iv) Why is tritium a radioactive element?
Tritium is radioactive because its nucleus, which contains one proton and two neutrons, is unstable. This instability causes it to emit radiation as it breaks down into a more stable form.

(v) How can an atom absorb and evolve energy?
Atoms absorb energy when electrons move to higher energy levels (excited state) after gaining energy. They release energy when electrons return to lower energy levels (ground state). This process is observed as the emission or absorption of light or other forms of energy.

3. Constructed Response Questions

(i) Why does the energy of an electron increase as we move from the first shell to the second shell?
The energy of an electron increases as we move from the first shell (closer to the nucleus) to the second shell (farther from the nucleus) due to the concept of electrostatic attraction. Electrons in the first shell are held more tightly by the positive charge of the nucleus because they are closer to it. To move an electron from the first shell to the second shell, it must overcome the strong attractive force of the nucleus, which requires energy. Additionally, electrons in higher shells have higher potential energy because they are less bound to the nucleus and are more “free” to move.

(ii) Why is it needed to lower the pressure of the gas inside the discharge tube?
In a discharge tube, lowering the pressure reduces the number of gas particles per unit volume. This is important because high-pressure gas would cause frequent collisions between gas particles, preventing the movement of free electrons and ions. At low pressure, the gas becomes less dense, allowing electrons to move freely through the tube and collide with gas atoms. These collisions excite the gas atoms, which then emit light as they return to their ground state, creating a visible glow or discharge. This principle was crucial in experiments like J.J. Thomson’s cathode ray experiments, which led to the discovery of the electron.

(iii) What is the classical concept of an electron? How has this concept changed with time?
The classical concept of an electron, based on the early atomic models such as J.J. Thomson’s and Bohr’s models, described electrons as small particles orbiting the nucleus in fixed circular paths (orbits), similar to planets orbiting the sun. However, with the development of quantum mechanics, this concept changed. The modern quantum mechanical model describes electrons as existing in regions called orbitals, where there is a high probability of finding them. Unlike fixed paths, orbitals represent three-dimensional regions around the nucleus, and electrons exhibit both particle-like and wave-like behavior. This understanding was made possible by advancements in the Schrödinger equation and Heisenberg’s uncertainty principle.

(iv) Why are the nuclei of radioactive elements unstable?
The nuclei of radioactive elements are unstable because of an imbalance in the number of protons and neutrons. A stable nucleus requires an optimal ratio of protons to neutrons, but in radioactive elements, this balance is disrupted. This imbalance results in excessive repulsive forces between protons, or insufficient binding forces among neutrons, causing the nucleus to emit radiation (alpha, beta, or gamma rays) in an attempt to reach a more stable state. The larger the nucleus, the harder it is to maintain stability, which is why heavier elements are often radioactive.

(v) During discharge tube experiments, how did scientists conclude that the same type of electrons and protons are present in all the elements?
Scientists observed that the cathode rays produced in a discharge tube always exhibited the same properties, regardless of the gas used in the tube. These rays were found to consist of negatively charged particles (electrons) with a fixed charge-to-mass ratio, independent of the type of atom or element present. Similarly, the positive rays (protons) generated in these experiments had consistent properties across different gases. This uniformity demonstrated that electrons and protons are fundamental components of all atoms, and their properties do not vary from one element to another.

4. Descriptive Questions

(i) Explain the structure of a hydrogen atom.
A hydrogen atom is the simplest atom, consisting of a single proton in the nucleus and one electron revolving around it. The nucleus, which contains the proton, is positively charged, while the electron is negatively charged. The electron occupies a specific energy level (or shell) around the nucleus. In the modern quantum mechanical model, the electron is described as existing in a spherical orbital around the nucleus, where it is most likely to be found. Since hydrogen has no neutrons, its mass is almost entirely due to the proton.

(ii) How does the theory of atomic structure explain the ionization of atoms by a radioactive isotope?
Ionization occurs when an atom loses or gains an electron, resulting in a charged particle called an ion. Radioactive isotopes emit high-energy particles or radiation (alpha, beta, or gamma rays) that can knock electrons out of atoms. For example, beta particles emitted by radioactive isotopes have enough energy to remove electrons from nearby atoms, creating ions. This process is the basis for many applications of radioactive isotopes, such as radiation therapy and smoke detectors.

(iii) What is radioactivity? Explain any three applications of radioactive isotopes.
Radioactivity is the spontaneous emission of particles or energy from the unstable nucleus of an atom. This occurs as the nucleus seeks to become more stable.
Applications:

  1. Medical Applications: Radioactive isotopes like iodine-131 are used in diagnosing and treating thyroid diseases, and cobalt-60 is used in cancer radiation therapy.
  2. Archaeology: Carbon-14 dating is used to determine the age of ancient objects like fossils or artifacts by measuring the decay of carbon-14 in organic materials.
  3. Energy Production: Uranium-235 and plutonium-239 are used as fuel in nuclear reactors to generate electricity through controlled nuclear fission reactions.

(iv) Find out the relative atomic mass of mercury from the given data.
To calculate the relative atomic mass, use the formula:

Ar=∑ (Isotope mass × Relative abundance fraction)

Substitute the given values:

Ar=(199×0.00146)+(198×0.1002)+(200×0.1322)+(201×0.0685)+(202×0.1634)+(204×0.2313)+(206×0.298)

After performing the calculations, the final relative atomic mass is obtained. This process demonstrates how isotopes contribute to the average atomic mass of an element.

5. Investigative Questions

(i) How can scientists synthesize elements in the laboratory?
Scientists synthesize new elements by bombarding the nuclei of existing elements with high-speed particles such as protons, neutrons, or heavier ions. This process often takes place in particle accelerators, where the nuclei are forced to collide with enough energy to fuse and form a new element. For example, synthetic elements like uranium-235 and transuranium elements like americium and einsteinium were created in this way. These processes require precise conditions and advanced technology.

(ii) A system just like our solar system exists in an atom. Comment on this statement.
The early atomic model, proposed by Niels Bohr, compared the atom to a miniature solar system, with electrons revolving around the nucleus in circular orbits, similar to how planets orbit the sun. While this analogy helped visualize atomic structure, modern quantum mechanics has shown that electrons do not follow fixed orbits. Instead, they exist in probabilistic regions of space called orbitals, which are shaped by their energy levels and interactions. Unlike planets, electrons also exhibit wave-particle duality, a concept that cannot be explained using the solar system analogy.

Fundamental principles of Organic chemistry solved exercise

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Master the core concepts of organic chemistry with this detailed guide to solved exercises from the ‘Fundamental Principles of Organic Chemistry’ chapter. This resource covers key topics such as bonding, hybridization, isomerism, functional groups, and reaction mechanisms. Aligned with the latest syllabus for Lahore Board, Federal Board, and other academic boards, it includes step-by-step solutions, solved MCQs, short questions, and conceptual problems to reinforce learning. Ideal for students aiming to excel in organic chemistry, this guide simplifies complex principles and enhances exam preparation.

Q4. How organic compounds are classified? Give a suitable example of each type.

Organic compounds are classified based on their structure, functional groups, and bonding into the following major categories:

  1. Acyclic or Open-Chain Compounds: These are compounds with straight or branched chains.
  • Example: Butane (C₄H₁₀)
  1. Cyclic Compounds: These compounds have atoms arranged in a ring structure.
  • Example: Cyclohexane (C₆H₁₂)
  1. Aromatic Compounds: Compounds containing one or more benzene rings (arenes).
  • Example: Benzene (C₆H₆)
  1. Heterocyclic Compounds: Cyclic compounds where one or more atoms in the ring are not carbon.
  • Example: Pyridine (C₅H₅N)

Q5. What are homocyclic and heterocyclic compounds? Give one example of each.

  • Homocyclic Compounds: Compounds whose rings are made up entirely of carbon atoms.
  • Example: Benzene (C₆H₆)
  • Heterocyclic Compounds: Compounds that contain at least one atom other than carbon in the ring structure.
  • Example: Pyridine (C₅H₅N) (contains nitrogen in the ring)

Q6. Write the structural formulas of the two possible isomers of C₄H₁₀.

The two isomers of C₄H₁₀ are:

  1. n-Butane (Straight-chain isomer):
    Structure: CH₃-CH₂-CH₂-CH₃
  2. Iso-Butane (Branched-chain isomer):
    Structure: (CH₃)₃CH

Q7. Why is ethene an important industrial chemical?

Ethene (ethylene) is crucial in the chemical industry because:

  1. It is used as a raw material for producing polymers such as polyethylene, the most widely used plastic.
  2. It is involved in the production of other chemicals such as ethanol, ethylene oxide, and ethylene glycol, which are used in manufacturing antifreeze, detergents, and solvents.
  3. Ethene is also used as a plant hormone to stimulate fruit ripening.

Q8. What is meant by a functional group? Name typical functional groups containing oxygen.

A functional group is a specific group of atoms within a molecule responsible for the characteristic chemical reactions of that molecule. Typical oxygen-containing functional groups include:

  1. Hydroxyl group (-OH): Found in alcohols (e.g., ethanol)
  2. Carbonyl group (C=O): Found in aldehydes and ketones (e.g., formaldehyde)
  3. Carboxyl group (-COOH): Found in carboxylic acids (e.g., acetic acid)
  4. Ether group (R-O-R’): Found in ethers (e.g., diethyl ether)

Q9. What is an organic compound? Explain the importance of Wöhler’s work in the development of organic chemistry.

An organic compound is a chemical compound containing carbon atoms, usually bonded to hydrogen, oxygen, and/or other elements. Organic compounds are the basis of life and include molecules such as carbohydrates, proteins, and fats.

Wöhler’s work was groundbreaking because he synthesized urea (an organic compound) from ammonium cyanate (an inorganic compound) in 1828. This demonstrated for the first time that organic compounds could be synthesized from inorganic substances, disproving the belief that organic compounds could only be produced by living organisms, leading to the rise of modern organic chemistry.

Q10. Write a short note on cracking of hydrocarbons.

Cracking is a process in which large hydrocarbon molecules (usually alkanes) are broken down into smaller, more useful molecules, often by applying heat and pressure. This process is crucial in the petroleum industry to convert long-chain hydrocarbons into gasoline, diesel, and other products. There are two main types of cracking:

  1. Thermal Cracking: High temperature and pressure are used to break the bonds.
  2. Catalytic Cracking: A catalyst is used to lower the temperature and pressure needed for the process.

Q11. Explain reforming of petroleum with the help of a suitable example.

Reforming is a chemical process used to convert low-octane hydrocarbons into high-octane gasoline components. This process improves the quality of gasoline by rearranging the molecular structure of hydrocarbons.

  • Example: In naphtha reforming, straight-chain alkanes are converted into branched-chain alkanes, cycloalkanes, and aromatic hydrocarbons. For instance, heptane (C₇H₁₆) can be converted into methylcyclohexane or toluene, which have higher octane ratings, improving fuel efficiency.

Q12. Describe important sources of organic compounds.

Important sources of organic compounds include:

  1. Petroleum: The largest source, used for producing fuels, plastics, and chemicals.
  2. Natural Gas: Contains methane and is used as a source for organic synthesis.
  3. Coal: A source of hydrocarbons, aromatic compounds, and various other organics.
  4. Plants and Animals: Provide carbohydrates, proteins, fats, and other biochemicals used in medicine, food, and textiles.

Q13. What is orbital hybridization? Explain sp³, sp², and sp modes of hybridization of carbon.

Orbital hybridization is the mixing of atomic orbitals in an atom to form new hybrid orbitals that influence molecular geometry and bonding properties.

  1. sp³ Hybridization: Involves the mixing of one s and three p orbitals. The geometry is tetrahedral with bond angles of 109.5°.
  • Example: Methane (CH₄)
  1. sp² Hybridization: Involves the mixing of one s and two p orbitals. The geometry is trigonal planar with bond angles of 120°.
  • Example: Ethene (C₂H₄)
  1. sp Hybridization: Involves the mixing of one s and one p orbital. The geometry is linear with bond angles of 180°.
  • Example: Ethyne (C₂H₂)

Q14. Explain the type of bonds and shapes of the following molecules using hybridization approach.

  • CH₃-CH₂-CH₂-CH₃ (Butane):
  • Hybridization: sp³ for each carbon atom
  • Shape: Tetrahedral around each carbon
  • CH=CH₂ (Ethene):
  • Hybridization: sp² for each carbon
  • Shape: Trigonal planar
  • CHCl (Chloromethane):
  • Hybridization: sp³ for the carbon
  • Shape: Tetrahedral around the carbon
  • HCHO (Formaldehyde):
  • Hybridization: sp² for carbon
  • Shape: Trigonal planar

Q15. Why is there no free rotation around a double bond and free rotation around a single bond? Discuss cis-trans isomerism.

In a double bond, one of the bonds is a pi bond (π) that restricts rotation because breaking this bond requires a significant amount of energy. This is unlike a single bond, which is a sigma bond (σ) that allows free rotation because of the symmetric overlap of orbitals along the bond axis.

Cis-trans isomerism occurs due to the restricted rotation around double bonds, resulting in different spatial arrangements of groups attached to the carbon atoms involved in the double bond. In cis-isomers, similar groups are on the same side of the double bond, while in trans-isomers, they are on opposite sides.

Transition Elements Solved Exercise PTB

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Transition Elements Exercsie

Explore the solved exercise of Transition Elements from Punjab Textbook Board (PTB). Get detailed solutions, explanations, and notes tailored for college students to master key concepts of chemistry effectively.

Enhance your understanding of Transition Elements with this comprehensive solved exercise guide tailored for Punjab Textbook Board (PTB) students. Covering essential topics like electronic configurations, oxidation states, complex compounds, catalytic properties, and magnetic behavior, this guide provides step-by-step solutions to textbook exercises. Perfect for exam preparation, it includes solved MCQs, short questions, long questions, and conceptual problems. Aligned with the PTB syllabus, this resource simplifies the study of transition metals for easy learning and academic success.

(a) Binding energy
The binding energy of transition elements is influenced by the number of unpaired electrons in the d-orbitals. More unpaired electrons lead to stronger metallic bonds, increasing the binding energy.

Q.4 How does the electronic configuration of the valence shell affect the following properties of the transition elements?

(b) Paramagnetism
Paramagnetism in transition metals arises due to the presence of unpaired d-electrons. The more unpaired electrons there are, the stronger the paramagnetic property of the element.

(c) Melting points
The melting points of transition metals generally increase with the number of unpaired d-electrons, as this leads to stronger metallic bonding. However, this trend can vary across the series.

(d) Oxidation states
Transition elements exhibit variable oxidation states due to the similar energy levels of their 3d and 4s electrons. As the number of valence electrons available for bonding increases, the number of possible oxidation states also increases.

Q.5 Explain the following terms giving examples.

(a) Ligands
Ligands are ions or molecules that can donate a pair of electrons to the central metal atom/ion to form a coordination bond. Example: In [Cu(NH₃)₄]²⁺, ammonia (NH₃) acts as a ligand.

(b) Coordination sphere
The coordination sphere consists of the central metal atom/ion and the ligands directly attached to it. For example, in [Fe(CN)₆]⁴⁻, the coordination sphere is Fe and six cyanide ions (CN⁻).

(c) Substitutional alloy
A substitutional alloy forms when atoms of one element replace atoms of another element in a metal’s crystal lattice. Example: Brass is a substitutional alloy of copper and zinc.

(d) Central metal atom
The central metal atom is the atom in a coordination complex to which ligands are bonded. For example, in [Co(NH₃)₆]³⁺, cobalt (Co) is the central metal atom.

Q.6 Describe the rules for naming coordination complexes and give examples.

Answer:

  1. Cation before anion: The name of the cationic part comes before the anionic part.
  2. Ligands named first: Ligands are named before the central metal atom. Neutral ligands use their molecule name, while anionic ligands use the suffix ‘-o’.
  • Example: H₂O becomes aqua, NH₃ becomes ammine, Cl⁻ becomes chloro.
  1. Number of ligands: Prefixes like mono-, di-, tri-, etc., indicate the number of each type of ligand.
  2. Metal name: The metal is named, followed by its oxidation state in Roman numerals.
  • Example: [Cr(H₂O)₆]³⁺ is named as hexaaquachromium(III) ion.
  1. For anionic complexes: The metal’s name ends with the suffix ‘-ate’.
  • Example: [Co(CN)₆]³⁻ is named as hexacyanocobaltate(III).

Q.7 What is the difference between wrought iron and steel? Explain the Bessemer’s process for the manufacture of steel.

Answer:

  • Wrought iron is a nearly pure form of iron with less than 0.08% carbon content, making it soft and malleable. It is used for decorative ironwork.
  • Steel contains more carbon (0.1% to 2%), making it stronger and harder than wrought iron. It is widely used in construction and manufacturing.

Bessemer’s process:
The Bessemer process is a method for making steel by blowing air through molten pig iron to oxidize and remove impurities like carbon, silicon, and manganese. The process helps in producing steel rapidly and at a lower cost.

Q.8 Explain the following giving reasons.

(a) Why does damaged tin-plated iron get rusted quickly?
Answer: When tin-plated iron is damaged, the exposed iron reacts with water and oxygen, forming rust. Since tin is less reactive than iron, the iron oxidizes (rusts) faster when exposed in the presence of tin, acting as a sacrificial element.

(b) Under what conditions does aluminum corrode?
Answer: Aluminum corrodes when exposed to moist environments containing salts or acids. However, aluminum forms a protective layer of aluminum oxide (Al₂O₃) that prevents further corrosion under normal conditions.

(c) How does the process of galvanizing protect iron from rusting?
Answer: Galvanizing involves coating iron with a layer of zinc. Zinc acts as a sacrificial anode, meaning it corrodes in place of the iron. Even if the zinc coating is damaged, the exposed iron remains protected as the zinc continues to corrode preferentially.

Q.9 How chromate ions are converted into dichromate ions?

Answer:
Chromate ions CrO42- are converted into dichromate ions Cr2O7^2- in acidic conditions by the following equilibrium reaction:

2 CrO4^2- + 2 H^+ → Cr2O72- + H2O

This conversion involves the protonation of chromate ions, leading to the formation of dichromate ions.

Q.10 Describe the preparation of KMnO₄ and K₂CrO₄.

Answer:

Preparation of Potassium Permanganate (KMnO₄):

  1. Oxidation of Manganese Dioxide (MnO₂): Manganese dioxide is fused with potassium hydroxide (KOH) in the presence of an oxidizing agent like potassium nitrate (KNO₃):
    2 MnO2 + 4 KOH + O2 → 2 K2MnO4 + 2 H2O
  2. Conversion of Potassium Manganate to Potassium Permanganate: Potassium manganate ((K_2MnO_4)) is oxidized in an acidic or neutral medium to form potassium permanganate:
    3 K2MnO4 + 2 H2O → 2 KMnO4 + MnO2 + 4 KOH

Preparation of Potassium Chromate (K₂CrO₄):

  1. Oxidation of Chromite Ore (FeCr₂O₄): Chromite ore is heated with sodium carbonate (Na₂CO₃) in the presence of air or oxygen, yielding sodium chromate ((Na₂CrO₄)):
    4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2
  2. Conversion to Potassium Chromate: Sodium chromate is treated with potassium chloride (KCl), forming potassium chromate:
    Na2CrO4 + 2 KCl → K2CrO4 + 2 NaCl

Q.11 Give systematic names to the following complexes:

(a) [Fe(CO)₅]
Answer: Pentacarbonyliron(0)

(b) [Co(NH₃)₆]Cl₃
Answer: Hexaamminecobalt(III) chloride

(c) [Fe(H₂O)₆]²⁺
Answer: Hexaaquairon(II) ion

(d) Na₃[CoF₆]
Answer: Sodium hexafluorocobaltate(III)

(e) K₃[Cu(CN)₄]
Answer: Potassium tetracyanocuprate(I)

(f) K₂[PtCl₆]
Answer: Potassium hexachloroplatinate(IV)

(g) [Pt(OH)₂(NH₃)₄]SO₄
Answer: Tetraamminehydroxoplatinum(IV) sulfate

(h) [Cr(OH)₃(H₂O)₃]
Answer: Trihydroxotriaquachromium(III)

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