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Water Solved Exercise Punjab Text Book

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Prepare effectively with solved exercises on water, designed for PTB curriculum. Cover essential topics like water properties, treatment processes, and industrial applications to boost your understanding and exam readiness.

Short Questions (Extended Answers)

  1. How water rises in plants?
    Water rises in plants through a combination of capillary action, root pressure, and transpiration. Capillary action is the movement of water within the narrow xylem vessels due to adhesion (attraction between water and vessel walls) and cohesion (attraction between water molecules). Transpiration from the leaves creates a negative pressure that pulls water upward from the roots.
  2. Which forces are responsible for dissolving polar substances in water?
    Polar substances dissolve in water mainly due to hydrogen bonding and dipole-dipole interactions. Water, being a polar molecule, has a partial positive charge on hydrogen and a partial negative charge on oxygen. This allows it to surround and interact with other polar molecules or ions, stabilizing them in solution.
  3. Why are non-polar compounds insoluble in water?
    Non-polar compounds do not dissolve in water because they lack polar groups that can form hydrogen bonds with water. Water molecules are more attracted to each other than to non-polar molecules, resulting in the separation of water and non-polar substances, such as oils.
  4. How does water dissolve sugar and alcohol?
    Water dissolves sugar and alcohol through hydrogen bonding. Both sugar and alcohol have hydroxyl (OH) groups, which can form hydrogen bonds with water molecules, allowing them to dissolve readily in water.
  5. How does limestone dissolve in water?
    Limestone, primarily composed of calcium carbonate (CaCO3), dissolves in water containing dissolved carbon dioxide (CO2). The CO2 reacts with water to form carbonic acid (H2CO3), which further reacts with calcium carbonate to form soluble calcium bicarbonate [Ca(HCO3)2].
  6. Differentiate between soft and hard water.
    Soft water contains little to no dissolved minerals like calcium and magnesium. In contrast, hard water has high concentrations of these minerals, which can cause scaling in pipes and reduce the effectiveness of soaps and detergents.
  7. What are the causes of hardness in water?
    Hardness is caused by the presence of dissolved calcium and magnesium ions, which originate from the weathering of rocks and minerals, such as limestone and dolomite.
  8. What are the effects of temporary hardness in water?
    Temporary hardness, caused by dissolved bicarbonate minerals, can lead to scale formation in kettles and boilers when heated. This hardness can be removed by boiling the water.
  9. Mention the disadvantages of detergents.
    Detergents contain synthetic chemicals that can harm aquatic life when they enter water bodies. They can reduce the surface tension of water, making it difficult for organisms to breathe, and may also accumulate in the environment, leading to toxic effects.
  10. What is the difference between biodegradable and non-biodegradable substances?
    Biodegradable substances can decompose naturally by the action of microorganisms, while non-biodegradable substances, such as plastics, persist in the environment and do not break down easily.
  11. How detergents make the water unfit for aquatic life?
    Detergents contain phosphates and other chemicals that can lead to eutrophication, where excessive nutrients cause algal blooms. These blooms deplete oxygen in the water, making it difficult for aquatic life to survive.
  12. Why are pesticides used?
    Pesticides are chemicals used to eliminate pests that damage crops, spread diseases, or harm livestock. They help in increasing agricultural productivity and protecting stored products.
  13. What are the reasons for waterborne diseases?
    Waterborne diseases are caused by the ingestion of water contaminated with pathogenic microorganisms, such as bacteria, viruses, and parasites. Common sources of contamination include sewage, agricultural runoff, and improper sanitation.
  14. How can waterborne diseases be prevented?
    Preventive measures include purifying drinking water through filtration, chlorination, or boiling; practicing good hygiene, such as washing hands regularly; and improving sanitation and waste management.

Extensive Questions (Detailed Answers)

  1. How does the polarity of a water molecule play its role in dissolving substances?
    The polarity of water means that it has a partial positive charge on one side (near the hydrogen atoms) and a partial negative charge on the other (near the oxygen atom). This allows water to interact with other polar molecules or ions. When an ionic compound, such as salt (NaCl), is added to water, the negative ends of the water molecules are attracted to the positive sodium ions, and the positive ends are attracted to the negative chloride ions. This attraction causes the ions to separate and become surrounded by water molecules, dissolving the salt. Similarly, polar covalent compounds, such as sugar, dissolve because their polar regions can form hydrogen bonds with water.
  2. Explain the methods of removing permanent hardness.
    Permanent hardness is caused by the presence of dissolved calcium and magnesium salts, such as chlorides and sulfates, that cannot be removed by boiling. Methods for removing permanent hardness include:
  • Ion-exchange resins: These replace calcium and magnesium ions with sodium or potassium ions, softening the water.
  • Adding washing soda (sodium carbonate): This reacts with the calcium and magnesium ions to form insoluble carbonates, which can then be removed.
  • Distillation: This process involves heating water to produce steam, which is then condensed back into liquid form, leaving the dissolved minerals behind.
  1. Explain water pollution due to industrial waste.
    Industrial waste can introduce harmful substances such as heavy metals (lead, mercury), toxic chemicals (pesticides, solvents), and organic pollutants (phenols, detergents) into water bodies. These pollutants can disrupt aquatic ecosystems, harm wildlife, and pose health risks to humans who consume contaminated water. The pollution may also alter the water’s pH, temperature, and turbidity, further impacting aquatic life.
  2. Justify the statement: household water is a reason for water pollution.
    Household water can contribute to pollution when it carries substances like detergents, oils, and pharmaceuticals into water bodies. Wastewater from households often contains organic matter, chemicals from cleaning products, and trace amounts of medications, which can disrupt aquatic ecosystems. Additionally, improper disposal of substances like cooking oils and paints can exacerbate water pollution.
  3. Explain how agricultural effluents are fatal for aquatic life.
    Agricultural runoff often contains fertilizers, pesticides, and animal waste, which can enter water bodies during rainfall or irrigation. Fertilizers rich in nitrogen and phosphorus cause eutrophication, leading to excessive algal growth that depletes oxygen in the water, resulting in “dead zones.” Pesticides can be toxic to aquatic organisms, affecting their reproduction and survival.
  4. Explain five important waterborne diseases and their prevention.
  • Cholera: Caused by Vibrio cholerae bacteria; prevention includes ensuring clean drinking water and good sanitation.
  • Typhoid: Caused by Salmonella typhi bacteria; vaccination and using safe drinking water can prevent it.
  • Dysentery: Often caused by Shigella bacteria; good hygiene and sanitation help prevent its spread.
  • Hepatitis A: A viral infection spread through contaminated water; vaccination and drinking purified water are preventive measures.
  • Giardiasis: Caused by the Giardia parasite; prevention includes avoiding untreated water and proper sanitation.
  1. Give some disadvantages of hard water.
    Hard water causes scale buildup in pipes and water heaters, reducing their efficiency. It can also decrease the effectiveness of soaps and detergents, requiring more product for cleaning. Additionally, it can leave mineral deposits on dishes, laundry, and fixtures.
  2. What is water pollution? Describe the effects of using polluted water.
    Water pollution refers to the contamination of water bodies by harmful substances. Using polluted water can lead to health issues like gastrointestinal diseases, skin irritations, and neurological problems. In agriculture, polluted water can reduce crop yields and contaminate food. It also negatively affects aquatic life by disrupting ecosystems and reducing biodiversity.
  3. Explain why water is considered a universal solvent.
    Water is known as a universal solvent because it can dissolve a wide range of substances. Its polarity allows it to interact with various ionic and polar compounds, making it essential for biochemical processes, nutrient transport, and industrial applications.
  4. Write a note on the treatment of sewage water.
    Sewage treatment involves multiple stages to remove contaminants:
  • Primary treatment: Physical removal of large solids through screening and sedimentation.
  • Secondary treatment: Biological processes where bacteria decompose organic matter.
  • Tertiary treatment: Chemical or physical processes to remove remaining contaminants, such as nitrogen, phosphorus, and pathogens. This step may involve disinfection using chlorine or UV light.
    Treated water is then either released into the environment or further purified for reuse.

The Atmosphere Solved Exercise 10th

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Prepare for 10th-grade exams with solved exercises on The Atmosphere. Cover key concepts like atmospheric layers, weather, and climate, with detailed solutions to enhance your understanding.

Short Answer Questions:

  1. Explain the phenomenon of decreasing temperature in the troposphere.
  • In the troposphere, the temperature decreases with altitude because the ground absorbs heat from the sun and warms the air above it. As you go higher, the distance from the heat source (Earth’s surface) increases, leading to lower temperatures.
  1. Differentiate between primary and secondary air pollutants.
  • Primary air pollutants are emitted directly from sources such as vehicles, factories, or natural processes (e.g., carbon monoxide, sulfur dioxide).
  • Secondary air pollutants form in the atmosphere through chemical reactions between primary pollutants and other components, like ozone and smog.
  1. State the major sources of CO and CO₂ emission.
  • CO (Carbon Monoxide): Emitted from vehicle exhausts, industrial processes, and incomplete combustion of fossil fuels.
  • CO₂ (Carbon Dioxide): Emitted from burning fossil fuels, deforestation, and respiration.
  1. CO₂ is responsible for heating up the atmosphere, how?
  • CO₂ traps heat in the atmosphere by absorbing infrared radiation emitted from the Earth’s surface, contributing to the greenhouse effect, which warms the planet.
  1. CO is a hidden enemy, explain its action.
  • Carbon monoxide (CO) is a colorless, odorless gas that can bind to hemoglobin in the blood, preventing the transport of oxygen and leading to poisoning or even death in high concentrations.
  1. What threats are to human health due to SO₂ gas as air pollutant?
  • Sulfur dioxide (SO₂) can cause respiratory problems, irritation of the eyes, worsening of asthma, and may lead to lung diseases with prolonged exposure.
  1. Which air pollutant is produced on anaerobic decomposition of organic matter?
  • Methane (CH₄) is produced during the anaerobic decomposition of organic matter in places like landfills and wetlands.
  1. How acid rain increases the acidity of soil?
  • Acid rain contains sulfuric and nitric acids, which lower the pH of the soil, leading to increased acidity. This can harm plant growth and soil organisms.
  1. Point out two serious effects of ozone depletion.
  • Increased UV radiation exposure, leading to skin cancer and eye cataracts.
  • Damage to marine ecosystems, especially affecting phytoplankton in the oceans.
  1. How ozone layer forms in the stratosphere?
    • The ozone layer forms when ultraviolet (UV) light splits oxygen molecules (O₂) into individual oxygen atoms (O), which then combine with other oxygen molecules to form ozone (O₃).
  2. Why are 75% of the atmospheric mass lies within the troposphere?
    • The troposphere contains most of the atmosphere’s water vapor and aerosols, and gravity pulls the atmospheric gases closer to Earth’s surface, concentrating most of the mass within this layer.
  3. How ozone layer is being depleted by chlorofluorocarbons?
    • Chlorofluorocarbons (CFCs) release chlorine atoms when they are broken down by UV light in the stratosphere. These chlorine atoms react with ozone, breaking it down into oxygen molecules, thereby depleting the ozone layer.

Long Answer Questions:

  1. Write down the significance of atmospheric gases.
  • Atmospheric gases such as nitrogen, oxygen, carbon dioxide, and argon play critical roles in supporting life on Earth. Oxygen is essential for respiration, carbon dioxide for photosynthesis, and nitrogen is a key component of the nitrogen cycle. The atmosphere also helps in regulating Earth’s temperature by absorbing and emitting thermal radiation.
  1. Give the characteristics of the troposphere. Why temperature decreases upwards in this sphere?
  • The troposphere is the lowest layer of the atmosphere, characterized by weather changes, cloud formation, and high concentrations of water vapor. The temperature decreases with altitude because the ground absorbs heat from the sun, and air is heated from the bottom up.
  1. What are the characteristics of the stratosphere? Why temperature increases upwards in this sphere?
  • The stratosphere lies above the troposphere and contains the ozone layer, which absorbs UV radiation, leading to higher temperatures with increasing altitude. This absorption of UV light heats the upper part of the stratosphere.
  1. CO₂ is necessary for plants but why its increasing concentration is alarming for us?
  • While CO₂ is essential for photosynthesis, excessive amounts contribute to global warming and climate change by enhancing the greenhouse effect, causing sea level rise and extreme weather events.
  1. Why is CO considered a health hazard?
  • Carbon monoxide (CO) is toxic because it binds to hemoglobin in red blood cells more effectively than oxygen does, reducing the blood’s ability to carry oxygen to body tissues and organs, leading to hypoxia and potentially fatal outcomes.
  1. Define acid rain. How it forms and what are its effects?
  • Acid rain is rain that has been made acidic due to the presence of sulfuric and nitric acids formed from sulfur dioxide (SO₂) and nitrogen oxides (NOx) in the atmosphere. It leads to damage to aquatic life, forest degradation, and erosion of buildings.
  1. Compounds of sulfur are air pollutants. Describe the sources of these compounds along with their effects.
  • Sources: Burning fossil fuels, industrial processes, and volcanic eruptions.
  • Effects: Respiratory problems, acid rain formation, and environmental damage.
  1. Where does ozone layer lie in atmosphere? How is it depleting and how can we prevent its depletion?
  • The ozone layer is located in the stratosphere, around 10-30 km above Earth’s surface. It is being depleted by chlorofluorocarbons (CFCs) and other ozone-depleting substances.
  • Prevention: Reducing the use of CFCs, promoting ozone-friendly products, and international agreements like the Montreal Protocol.
  1. Oxides of nitrogen cause air pollution. Describe the sources of these compounds.
  • Sources: Vehicle emissions, industrial processes, power plants, and lightning.
  • Effects: Formation of acid rain, photochemical smog, and respiratory issues in humans.

Environmental Chemistry Exercise10th PTB

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Prepare for your 10th-grade exams with solved exercises on Environmental Chemistry, based on the PTB curriculum. Focus on key concepts like pollution, environmental impact, and sustainable practices.

Short Answer Questions:

  1. Explain the phenomenon of decreasing temperature in the troposphere.
  • In the troposphere, the temperature decreases with altitude because the ground absorbs heat from the sun and warms the air above it. As you go higher, the distance from the heat source (Earth’s surface) increases, leading to lower temperatures.

2. Differentiate between primary and secondary air pollutants.

  • Primary air pollutants are emitted directly from sources such as vehicles, factories, or natural processes (e.g., carbon monoxide, sulfur dioxide).
  • Secondary air pollutants form in the atmosphere through chemical reactions between primary pollutants and other components, like ozone and smog.
  1. State the major sources of CO and CO₂ emission.
  • CO (Carbon Monoxide): Emitted from vehicle exhausts, industrial processes, and incomplete combustion of fossil fuels.
  • CO₂ (Carbon Dioxide): Emitted from burning fossil fuels, deforestation, and respiration.
  1. CO₂ is responsible for heating up the atmosphere, how?
  • CO₂ traps heat in the atmosphere by absorbing infrared radiation emitted from the Earth’s surface, contributing to the greenhouse effect, which warms the planet.
  1. CO is a hidden enemy, explain its action.
  • Carbon monoxide (CO) is a colorless, odorless gas that can bind to hemoglobin in the blood, preventing the transport of oxygen and leading to poisoning or even death in high concentrations.
  1. What threats are to human health due to SO₂ gas as air pollutant?
  • Sulfur dioxide (SO₂) can cause respiratory problems, irritation of the eyes, worsening of asthma, and may lead to lung diseases with prolonged exposure.
  1. Which air pollutant is produced on anaerobic decomposition of organic matter?
  • Methane (CH₄) is produced during the anaerobic decomposition of organic matter in places like landfills and wetlands.
  1. How acid rain increases the acidity of soil?
  • Acid rain contains sulfuric and nitric acids, which lower the pH of the soil, leading to increased acidity. This can harm plant growth and soil organisms.
  1. Point out two serious effects of ozone depletion.
  • Increased UV radiation exposure, leading to skin cancer and eye cataracts.
  • Damage to marine ecosystems, especially affecting phytoplankton in the oceans.
  1. How ozone layer forms in the stratosphere?
    • The ozone layer forms when ultraviolet (UV) light splits oxygen molecules (O₂) into individual oxygen atoms (O), which then combine with other oxygen molecules to form ozone (O₃).
  2. Why are 75% of the atmospheric mass lies within the troposphere?
    • The troposphere contains most of the atmosphere’s water vapor and aerosols, and gravity pulls the atmospheric gases closer to Earth’s surface, concentrating most of the mass within this layer.
  3. How ozone layer is being depleted by chlorofluorocarbons?
    • Chlorofluorocarbons (CFCs) release chlorine atoms when they are broken down by UV light in the stratosphere. These chlorine atoms react with ozone, breaking it down into oxygen molecules, thereby depleting the ozone layer.

Long Answer Questions:

  1. Write down the significance of atmospheric gases.
  • Atmospheric gases such as nitrogen, oxygen, carbon dioxide, and argon play critical roles in supporting life on Earth. Oxygen is essential for respiration, carbon dioxide for photosynthesis, and nitrogen is a key component of the nitrogen cycle. The atmosphere also helps in regulating Earth’s temperature by absorbing and emitting thermal radiation.
  1. Give the characteristics of the troposphere. Why temperature decreases upwards in this sphere?
  • The troposphere is the lowest layer of the atmosphere, characterized by weather changes, cloud formation, and high concentrations of water vapor. The temperature decreases with altitude because the ground absorbs heat from the sun, and air is heated from the bottom up.
  1. What are the characteristics of the stratosphere? Why temperature increases upwards in this sphere?
  • The stratosphere lies above the troposphere and contains the ozone layer, which absorbs UV radiation, leading to higher temperatures with increasing altitude. This absorption of UV light heats the upper part of the stratosphere.
  1. CO₂ is necessary for plants but why its increasing concentration is alarming for us?
  • While CO₂ is essential for photosynthesis, excessive amounts contribute to global warming and climate change by enhancing the greenhouse effect, causing sea level rise and extreme weather events.
  1. Why is CO considered a health hazard?
  • Carbon monoxide (CO) is toxic because it binds to hemoglobin in red blood cells more effectively than oxygen does, reducing the blood’s ability to carry oxygen to body tissues and organs, leading to hypoxia and potentially fatal outcomes.
  1. Define acid rain. How it forms and what are its effects?
  • Acid rain is rain that has been made acidic due to the presence of sulfuric and nitric acids formed from sulfur dioxide (SO₂) and nitrogen oxides (NOx) in the atmosphere. It leads to damage to aquatic life, forest degradation, and erosion of buildings.
  1. Compounds of sulfur are air pollutants. Describe the sources of these compounds along with their effects.
  • Sources: Burning fossil fuels, industrial processes, and volcanic eruptions.
  • Effects: Respiratory problems, acid rain formation, and environmental damage.
  1. Where does ozone layer lie in atmosphere? How is it depleting and how can we prevent its depletion?
  • The ozone layer is located in the stratosphere, around 10-30 km above Earth’s surface. It is being depleted by chlorofluorocarbons (CFCs) and other ozone-depleting substances.
  • Prevention: Reducing the use of CFCs, promoting ozone-friendly products, and international agreements like the Montreal Protocol.
  1. Oxides of nitrogen cause air pollution. Describe the sources of these compounds.
  • Sources: Vehicle emissions, industrial processes, power plants, and lightning.
  • Effects: Formation of acid rain, photochemical smog, and respiratory issues in humans.

Biochemistry Solved Exercise Punjab text book

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Biochemistry Exercise

Access comprehensive solutions to the Biochemistry exercise from Punjab Textbook Board. Simplified answers, detailed explanations, and helpful notes designed for college students to excel in their chemistry studies.

Short Answer Questions:

  1. How plants synthesize carbohydrates?
  • Plants synthesize carbohydrates through the process of photosynthesis, where carbon dioxide (CO₂) from the air and water (H₂O) from the soil react in the presence of sunlight and chlorophyll to form glucose (C₆H₁₂O₆) and oxygen (O₂). The general equation is:
    [ 6CO₂ + 6H₂O + sunlight →{chlorophyll} C₆H₁₂O₆ + 6O₂ ]
  1. Give the characteristics of monosaccharides.
  • Monosaccharides are the simplest form of carbohydrates, consisting of a single sugar unit. They are crystalline, water-soluble, and sweet-tasting. Examples include glucose, fructose, and galactose.
  1. What is the difference between glucose and fructose?
  • Glucose is an aldohexose (contains an aldehyde group), while fructose is a ketohexose (contains a ketone group). Although they have the same molecular formula (C₆H₁₂O₆), their structural arrangements differ.
  1. Give an example of a disaccharide. How is it hydrolyzed into monosaccharides?
  • An example of a disaccharide is sucrose. It is hydrolyzed into glucose and fructose in the presence of an enzyme (sucrase) or dilute acid by breaking the glycosidic bond.
  1. Give the characteristics of polysaccharides.
  • Polysaccharides are complex carbohydrates composed of long chains of monosaccharide units. They are generally insoluble in water, tasteless, and serve as energy storage (e.g., starch, glycogen) or structural components (e.g., cellulose).
  1. Where are the proteins found?
  • Proteins are found in various sources, including animal products (meat, dairy, eggs), plant sources (legumes, nuts, seeds), and are also present in every cell of living organisms.
  1. Describe the uses of carbohydrates.
  • Carbohydrates serve as a primary source of energy for the body, act as dietary fiber for digestion, and are used in the formation of cell structures (e.g., cellulose in plant cell walls).
  1. Lactose is disaccharide; which monosaccharides are present in it?
  • Lactose is composed of glucose and galactose.
  1. Why are the ten amino acids essential for us?
  • The ten essential amino acids cannot be synthesized by the human body and must be obtained from the diet to support protein synthesis and overall metabolism.
  1. How are proteins formed?
    • Proteins are formed by the polymerization of amino acids, linked together by peptide bonds to form polypeptide chains, which then fold into specific three-dimensional structures.
  2. How is gelatin obtained?
    • Gelatin is obtained by the hydrolysis of collagen, a protein found in the skin, bones, and connective tissues of animals.
  3. Give the general formula of the lipids.
    • The general formula for simple lipids (triglycerides) is RCOOR’, where R and R’ are fatty acid chains.
  4. Name two fatty acids with their formulae.
    • Palmitic acid (C₁₆H₃₂O₂)
    • Oleic acid (C₁₈H₃₄O₂)
  5. Give the types of vitamins.
    • Fat-soluble vitamins: A, D, E, K
    • Water-soluble vitamins: B-complex, C
  6. What is the significance of vitamins?
    • Vitamins are essential nutrients that the body needs in small amounts to maintain health, support metabolic processes, and prevent deficiency diseases.
  7. Describe the sources and uses of vitamin A.
    • Sources: Carrots, liver, dairy products, and leafy green vegetables.
    • Uses: Essential for vision, immune function, and skin health.
  8. Justify that water-soluble vitamins are not injurious to health.
    • Water-soluble vitamins (e.g., vitamin C, B-complex) are not stored in the body in large amounts and are easily excreted through urine, reducing the risk of toxicity.
  9. What do you mean by the genetic code of life?
    • The genetic code refers to the sequence of nucleotides in DNA that dictates the sequence of amino acids in proteins, thus determining the traits and functioning of living organisms.
  10. What is the function of DNA?
    • DNA serves as the genetic material, carrying instructions for the development, functioning, growth, and reproduction of all living organisms.
  11. How do you justify that RNA works like a messenger?
    • RNA acts as a messenger by transcribing genetic information from DNA and translating it into proteins during the process of protein synthesis.

Long Answer Questions:

  1. What are carbohydrates? How monosaccharides are prepared? Give their characteristics.
  • Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, usually in the ratio 1:2:1. They serve as a major energy source and structural material in living organisms.
  • Monosaccharides are prepared through hydrolysis of disaccharides or polysaccharides. For example, hydrolyzing starch can yield glucose.
  • Characteristics: Monosaccharides are sweet-tasting, crystalline solids, and soluble in water.
  1. Explain oligosaccharides.
  • Oligosaccharides consist of 2-10 monosaccharide units linked together. They are found in various natural sources and play a role in cell recognition and immune response.
  1. What are polysaccharides? Give their properties.
  • Polysaccharides are long chains of monosaccharide units. They are generally insoluble in water, non-sweet, and serve as energy storage (e.g., glycogen, starch) or structural materials (e.g., cellulose).
  1. Explain the sources and uses of proteins.
  • Sources: Animal products (meat, fish, eggs), legumes, nuts, and seeds.
  • Uses: Proteins are essential for growth and repair, enzyme formation, immune function, and transport of molecules in the body.
  1. Explain that amino acids are building blocks of proteins.
  • Amino acids link together through peptide bonds to form polypeptide chains, which fold into functional proteins. They are considered the fundamental units in protein synthesis.
  1. Explain the sources and uses of lipids.
  • Sources: Animal fats, vegetable oils, nuts, and seeds.
  • Uses: Lipids serve as an energy reserve, structural component of cell membranes, and precursors of hormones.
  1. Give the importance of vitamins.
  • Vitamins are critical for metabolic processes, preventing deficiency diseases, supporting immune function, and maintaining healthy skin, bones, and eyes.
  1. Describe the sources, uses, and deficiency symptoms of water-soluble vitamins.
  • Sources: Fruits, vegetables, whole grains, and legumes.
  • Uses: Support energy metabolism, nerve function, and collagen formation.
  • Deficiency symptoms: May include fatigue (vitamin B deficiency), scurvy (vitamin C deficiency), neurological problems (vitamin B12 deficiency).

Hydrocarbons Exercise solved

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Enhance your understanding of hydrocarbons with solved exercises. Cover key topics like types of hydrocarbons, reactions, and properties to reinforce your knowledge and excel in exams.

Short Questions:

  1. Differentiate between saturated and unsaturated hydrocarbons.
  • Saturated hydrocarbons: Contain only single bonds between carbon atoms (e.g., alkanes).
  • Unsaturated hydrocarbons: Contain one or more double or triple bonds between carbon atoms (e.g., alkenes and alkynes).
  1. A compound consisting of four carbon atoms has a triple bond in it. How many hydrogen atoms are present in it?
  • The compound is butyne (C₄H₆). There are 6 hydrogen atoms.
  1. Why are the alkanes called ‘paraffins’?
  • Alkanes are called paraffins because they are relatively unreactive due to the presence of only single bonds between carbon atoms, making them resistant to chemical reactions.
  1. What do you know about hydrogenation of alkenes?
  • Hydrogenation of alkenes is a chemical reaction in which hydrogen (H₂) is added across the double bond of alkenes, converting them into alkanes.
  1. How are alkyl halides reduced?
  • Alkyl halides can be reduced by reagents such as zinc and hydrochloric acid (Zn/HCl) to alkanes.
  1. Why are the alkanes used as fuel?
  • Alkanes are used as fuels because they release a large amount of energy when burned, producing carbon dioxide and water.
  1. How can you prepare ethene from alcohol and ethyl bromide?
  • From alcohol: Ethene can be prepared by dehydrating ethanol (C₂H₅OH) using concentrated sulfuric acid (H₂SO₄).
  • From ethyl bromide: Ethene can be prepared by treating ethyl bromide (C₂H₅Br) with alcoholic KOH, leading to elimination of HBr.
  1. Identify propane from propene with a chemical test.
  • Propene decolorizes bromine water, while propane does not react with bromine water.
  1. Why are the alkenes called ‘olefins’?
  • Alkenes are called olefins because they form oily liquids when reacted with halogens such as chlorine.
  1. Why alkane can’t be oxidized with KMnO₄ solution?
    • Alkanes are saturated hydrocarbons and do not have any reactive sites like double or triple bonds, so they do not react with strong oxidizing agents like potassium permanganate (KMnO₄).
  2. What are the addition reactions? Explain with an example.
    • Addition reactions: In these reactions, atoms or groups of atoms are added to the double or triple bond of unsaturated compounds.
      Example: Ethene (C₂H₄) reacts with bromine (Br₂) to form 1,2-dibromoethane (C₂H₄Br₂).
  3. Justify that alkanes give substitution reactions.
    • Alkanes undergo substitution reactions where a hydrogen atom is replaced by a halogen in the presence of light (e.g., methane reacts with chlorine to form chloromethane and hydrogen chloride).
  4. Both alkenes and alkynes are unsaturated hydrocarbons. State the one most significant difference between them.
    • Alkenes contain at least one double bond, while alkynes contain at least one triple bond.
  5. Write the molecular, dot and cross, and structural formula of ethyne.
    • Molecular formula: C₂H₂
    • Dot and cross diagram: Two carbon atoms with a triple bond between them, each bonded to a hydrogen atom.
    • Structural formula: H−C≡C−H
  6. Why are hydrocarbons soluble in organic solvents?
    • Hydrocarbons are nonpolar molecules and are soluble in organic solvents, which are also nonpolar, following the principle “like dissolves like.”
  7. Give the physical properties of alkanes.
    • Alkanes are colorless, odorless (for the lower members), nonpolar, insoluble in water, and have low boiling and melting points.
  8. How can you identify ethene from ethane?
    • Ethene decolorizes bromine water, whereas ethane does not.
  9. Why does the color of bromine water discharge on the addition of ethene in it?
    • The double bond in ethene reacts with bromine, leading to the formation of a colorless dibromo compound, thus discharging the color of bromine water.
  10. State one important use of each:
    • Ethene: Used in the production of polyethylene (a plastic).
    • Acetylene: Used in welding (oxyacetylene welding).
    • Chloroform: Used as a solvent in laboratories.
    • Carbon tetrachloride: Used as a cleaning agent and fire extinguisher.

Extensive Questions:

  1. What type of reactions are given by alkanes? Explain with reference to halogenation of alkanes.
  • Alkanes undergo substitution reactions, particularly halogenation, where a hydrogen atom is replaced by a halogen atom. For example, methane reacts with chlorine under UV light to form chloromethane and hydrogen chloride.
  1. Alkanes are a source of heat. Explain it.
  • Alkanes are used as fuels because, when combusted, they release large amounts of heat due to the exothermic nature of the combustion reaction, producing carbon dioxide and water.
  1. Prepare the following as directed:
  • (i) Ethene from ethane: Ethene can be prepared by dehydrogenation of ethane.
  • (ii) Acetylene from tetrahalide: Acetylene can be prepared by treating a tetrahalide like 1,2-dibromoethane with alcoholic KOH.
  • (iii) Carbon tetrachloride from methane: Methane reacts with chlorine in the presence of UV light to form carbon tetrachloride.
  • (iv) Ethylene glycol from ethene: Ethene reacts with water in the presence of oxygen to form ethylene glycol.
  • (v) 1,2-Dibromoethane from ethene: Ethene reacts with bromine to form 1,2-dibromoethane.
  • (vi) Glyoxal from acetylene: Acetylene can be oxidized with potassium permanganate to form glyoxal (C₂H₂O₂).

4. Explain the oxidation of acetylene.

  • Acetylene (C₂H₂) can undergo oxidation in different ways:
    • Controlled oxidation: Under controlled conditions, acetylene can be oxidized to form products like acetaldehyde or acetic acid using catalysts.
    • Combustion: When acetylene is burnt in air or oxygen, it undergoes complete oxidation to form carbon dioxide (CO₂) and water (H₂O).
      2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

5. Write balanced chemical equations for the following reactions. Also, name the products that are formed.

  • (i) A mixture of ethyne and hydrogen is passed over heated nickel:
  • C₂H₂ + 2H₂ →{Ni} C₂H₆
    Product: Ethane (C₂H₆).
  • (ii) Ethyne is treated with chlorine:
    C₂H₂ + Cl₂ → C₂H₂Cl₂
    Product: 1,2-Dichloroethene (if further chlorination occurs, it can form tetrachloroethane).
  • (iii) Ethyne is burnt in air:
    2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O
    Products: Carbon dioxide (CO₂) and water (H₂O).
  • (iv) Ethyne is passed through bromine water:
    C₂H₂ + Br₂ → C₂H₂Br₂
    Product: 1,2-Dibromoethene.

6. Explain briefly:

  • (i) Why butane undergoes substitution reactions?
    • Butane, as a saturated hydrocarbon (alkane), has single bonds, making it more likely to undergo substitution reactions rather than addition reactions.
  • (ii) There are millions of organic compounds.
    • The vast number of organic compounds is due to the ability of carbon atoms to form long chains, branched structures, and rings, along with multiple types of bonds (single, double, triple) and the presence of various functional groups.
  • (iii) Acetylene undergoes addition reactions in two stages.
    • Acetylene (C₂H₂) has a triple bond, allowing it to add atoms in two stages: first converting the triple bond to a double bond (forming a di-substituted alkene), and then to a single bond (forming a tetra-substituted alkane).
  • (iv) Alkynes are more reactive than alkanes.
    • Alkynes have a triple bond, which is more reactive than the single bonds in alkanes. The electron density in the triple bond makes alkynes more susceptible to addition reactions.

Organic Chemistry Solved Exercise PTB

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Prepare for exams with solved exercises on Organic Chemistry, designed according to the PTB curriculum. Cover key topics like functional groups, reactions, and isomerism to boost your understanding.

Short Questions:

1. What is meant by the term catenation? Give an example of a compound that displays catenation.

  • Catenation is the ability of an element, particularly carbon, to form long chains and rings by bonding with atoms of the same element. This property allows for the formation of a vast variety of organic compounds.
  • Example: Alkanes like hexane (C₆H₁₄) show catenation as they consist of long chains of carbon atoms.

2. How is coal formed?

  • Coal formation occurs over millions of years from the remains of plants that have been buried under sediment. The high temperature and pressure conditions cause chemical and physical changes, transforming the plant material into peat, then into lignite, and finally into coal.

3. What is the importance of natural gas?

  • Natural gas is a crucial energy source. It is used for heating, electricity generation, and as a fuel for vehicles. It is also a raw material in the production of chemicals, fertilizers, and hydrogen.

4. Justify that organic compounds are used as food.

  • Organic compounds, such as carbohydrates, proteins, and fats, are essential nutrients found in food that provide energy and are necessary for growth and the maintenance of life.

5. How are alkyl radicals formed? Explain with examples.

  • Alkyl radicals are formed by the removal of one hydrogen atom from an alkane.
  • Example: Removing a hydrogen atom from methane (CH₄) forms a methyl radical (CH₃·).

6. What is the difference between n-propyl and isopropyl radicals? Explain with structure.

  • n-Propyl radical: It is derived from propane by removing a hydrogen atom from the terminal carbon (CH₃-CH₂-CH₂·).
  • Isopropyl radical: It is formed by removing a hydrogen atom from the middle carbon of propane (CH₃-CH·-CH₃).

7. Explain different radicals of butane.

  • Butane can form two types of radicals:
  • n-Butyl radical: Formed by removing a hydrogen atom from the terminal carbon (CH₃-CH₂-CH₂-CH₂·).
  • sec-Butyl radical: Formed by removing a hydrogen from the second carbon (CH₃-CH₂-CH·-CH₃).
  • iso-Butyl radical: Formed by removing a hydrogen atom from the branch carbon (CH₃-CH·-CH₃).
  • tert-Butyl radical: Formed by removing a hydrogen atom from the central carbon (C·(CH₃)₃).

8. Define functional group with an example.

  • A functional group is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule.
  • Example: The hydroxyl group (-OH) in alcohols.

9. What is an ester group? Write down the formula of ethyl acetate.

  • An ester group has the structure -COO-, where a carbonyl (C=O) is bonded to an oxygen atom that is also bonded to another carbon chain.
  • Formula of ethyl acetate: CH₃COOCH₂CH₃.

10. Write down the dot and cross formulae of propane and n-butane.

  • Propane (C₃H₈): Show three carbon atoms bonded with eight hydrogen atoms in a linear chain arrangement.
  • n-Butane (C₄H₁₀): Show four carbon atoms bonded with ten hydrogen atoms in a linear chain arrangement.

11. Define structural formula. Draw the structural formulae of n-butane and isobutane.

  • A structural formula represents the arrangement of atoms within a molecule, showing how they are connected.
  • n-Butane: CH₃-CH₂-CH₂-CH₃
  • Isobutane: (CH₃)₂CH-CH₃

12. Write classification of coal.

  • Coal classification:
  • Peat: Early stage, with low carbon content.
  • Lignite: Soft coal with higher carbon than peat.
  • Bituminous coal: Harder with more carbon, commonly used in industries.
  • Anthracite: Highest carbon content, hardest type.

13. What are heterocyclic compounds? Give two examples.

  • Heterocyclic compounds are organic compounds containing rings that include atoms other than carbon, such as nitrogen, oxygen, or sulfur.
  • Examples: Pyridine and furan.

14. Why are benzene and other homologous compounds of benzene called aromatic compounds?

  • Benzene and its homologs are called aromatic compounds because they contain a conjugated system of pi electrons that are delocalized over the ring structure, making them stable and often having a distinct aroma.

Extensive Questions:

1. (a) How is coal formed? What are the different types of coal?

  • Coal formation occurs from dead plant material that is buried and subjected to high pressure and temperature over millions of years.
  • Types of coal:
  • Peat
  • Lignite
  • Bituminous coal
  • Anthracite

1. (b) Write down the composition and uses of different types of coal.

  • Peat: Low carbon, used as a fuel in some regions.
  • Lignite: 25-35% carbon, used for electricity generation.
  • Bituminous coal: 45-86% carbon, used in industry and electricity generation.
  • Anthracite: Over 86% carbon, used for heating.

2. What is destructive distillation of coal?

  • Destructive distillation is the process of heating coal in the absence of air to break it down into products like coke, coal tar, and ammonia.

3. Write a detailed note on functional groups of alkenes and alkynes. How are they identified from other compounds?

  • Alkenes contain a carbon-carbon double bond (C=C), while alkynes have a carbon-carbon triple bond (C≡C).
  • They can be identified by their unsaturation, which gives them characteristic reactions like addition reactions.

4. Give some uses of organic compounds in our daily life.

  • Organic compounds are used in medicines, food additives, fuels, and cosmetics.

5. Write down the characteristics of homologous series.

  • Homologous series have similar structures, gradual variation in physical properties, and the same functional group.

6. Why are organic compounds numerous?

  • The catenation ability of carbon, along with various functional groups, allows for the formation of a vast array of compounds.

7. What are amines? Explain the different types of amines giving an example of each type.

  • Amines are organic derivatives of ammonia, classified as:
  • Primary amines (R-NH₂): e.g., Methylamine.
  • Secondary amines (R₂-NH): e.g., Dimethylamine.
  • Tertiary amines (R₃-N): e.g., Trimethylamine.

8. Describe the functional group of an alcohol. How are alcoholic groups identified?

  • Alcohol functional group: -OH (hydroxyl group).
  • Identified by their reaction with sodium, forming hydrogen gas, or by oxidation to carbonyl compounds.

9. Differentiate between aldehydic and ketonic functional groups. How are both identified from each other?

  • Aldehydes (R-CHO) have the carbonyl group at the end of the carbon chain, while ketones (R-CO-R’) have the carbonyl group within the chain.
  • Tests: Tollens’ test gives a silver mirror with aldehydes but not with ketones.

10. Identify the functional groups in the following compounds. Also give the names of the functional groups:

  • Vinegar: Carboxylic acid (-COOH)
  • Ant sting: Formic acid (HCOOH)
  • Citrus fruit: Citric acid (carboxylic acid groups)
  • Sour milk: Lactic acid (carboxylic and hydroxyl groups)Here are the answers to the exercise questions as per the given numbering:

Acids, Bases and Salts Solved Exercise ptb

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Prepare for PTB exams with solved exercises on Acids, Bases, and Salts. Understand key concepts like pH, acid-base reactions, and salt formation through detailed solutions and explanations.

1. Name three common household substances having:
a. pH value greater than 7:

  • Baking soda (sodium bicarbonate)
  • Soap
  • Bleach b. pH value less than 7:
  • Vinegar (acetic acid)
  • Lemon juice
  • Milk c. pH value equal to 7:
  • Distilled water

2. Define a base and explain that all alkalis are bases, but all bases are not alkalis.
A base is a substance that can accept protons (H⁺ ions) or donate electron pairs. Alkalis are a subset of bases that are soluble in water and release hydroxide ions (OH⁻) in solution. Thus, while all alkalis are bases, not all bases dissolve in water to form an alkaline solution (e.g., ammonia is a base but not an alkali because it is weak and does not fully dissolve in water).

3. Define Bronsted-Lowry base and explain with an example that water is a Bronsted-Lowry base.
A Bronsted-Lowry base is a substance that can accept protons (H⁺ ions) during a chemical reaction. Water can act as a Bronsted-Lowry base because it accepts a proton from an acid.
For example, in the reaction between hydrochloric acid (HCl) and water:
HCl + H2O → H3O^+ + Cl^-

Water accepts a proton from HCl and forms the hydronium ion (H₃O⁺).

4. How can you justify that Bronsted-Lowry concept of acid and base is applicable to non-aqueous solutions?
The Bronsted-Lowry concept is based on proton transfer and does not require water as a solvent. For instance, in liquid ammonia (a non-aqueous solvent), ammonium ions (NH₄⁺) act as acids, and ammonia (NH₃) acts as a base according to the Bronsted-Lowry theory:

5. Which kind of bond is formed between Lewis acid and a base?
A coordinate covalent bond (or dative bond) is formed when a Lewis base donates a pair of electrons to a Lewis acid.

6. Why H⁺ ion acts as a Lewis acid?
The H⁺ ion acts as a Lewis acid because it lacks electrons and can accept a pair of electrons from a Lewis base to form a bond.

7. Name two acids used in the manufacture of fertilizers.

  • Sulfuric acid (H₂SO₄)
  • Nitric acid (HNO₃)

8. Define pH. What is the pH of pure water?
pH is the negative logarithm of the hydrogen ion concentration ([H^+]) in a solution, representing its acidity or alkalinity. The pH of pure water is 7, which is neutral.

9. How many times a solution of pH 1 will be stronger than that of a solution having pH 2?
A solution with a pH of 1 is 10 times more acidic than a solution with a pH of 2 because each pH unit represents a tenfold difference in hydrogen ion concentration.

10. Define the followings:
i. Normal salt: A salt formed by the complete neutralization of an acid by a base, e.g., sodium chloride (NaCl).
ii. Basic salt: A salt that contains hydroxide ions (OH⁻) or can produce them in water, e.g., sodium bicarbonate (NaHCO₃).

11. Na₂SO₄ is a neutral salt while NaHSO₄ is an acid salt. Justify.
Sodium sulfate (Na₂SO₄) is a neutral salt because it is formed from a strong acid (H₂SO₄) and a strong base (NaOH), which neutralize each other completely. Sodium bisulfate (NaHSO₄), on the other hand, is an acidic salt because it still contains an acidic hydrogen (HSO₄⁻) that can donate protons in solution.

12. Give a few characteristic properties of salts.

  • Salts are ionic compounds.
  • They are usually solid and crystalline at room temperature.
  • Many salts are soluble in water, producing ions.
  • Salts conduct electricity when dissolved in water or molten.
  • They have high melting and boiling points.

13. How are the soluble salts recovered from water?
Soluble salts can be recovered from water through processes such as evaporation or crystallization, where water is evaporated, leaving the dissolved salt behind.

14. How are the insoluble salts prepared?
Insoluble salts can be prepared by a precipitation reaction, where two aqueous solutions containing ions react to form a solid salt.
For example:

AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq)

15. Why is a salt neutral? Explain with an example.
A salt is neutral when it is formed from the reaction between a strong acid and a strong base, resulting in a neutral pH solution.
Example: Sodium chloride (NaCl) is neutral because it is formed from hydrochloric acid (HCl) and sodium hydroxide (NaOH), both strong and completely dissociating in water.

16. Name an acid used in the preservation of food.
Acetic acid (CH₃COOH), found in vinegar, is commonly used in the preservation of food.

17. Name the acids present in:
i. Vinegar: Acetic acid (CH₃COOH)
ii. Ant sting: Formic acid (HCOOH)
iii. Citrus fruit: Citric acid (C₆H₈O₇)
iv. Sour milk: Lactic acid (C₃H₆O₃)

18. How can you justify that Pb(OH)NO₃ is a basic salt?
Lead hydroxynitrate (Pb(OH)NO₃) is considered a basic salt because it contains hydroxide ions (OH⁻) in its structure, which makes it capable of neutralizing acids.

19. You are in need of an acidic salt. How can you prepare it?
An acidic salt can be prepared by the partial neutralization of a polybasic acid with a base. For example, by reacting sulfuric acid (H₂SO₄) with sodium hydroxide (NaOH) in a 1:1 molar ratio, you get sodium bisulfate (NaHSO₄), an acidic salt.

20. Which salt is used to prepare plaster of Paris?
Plaster of Paris is prepared from calcium sulfate hemihydrate (CaSO₄·0.5H₂O).

Extensive Questions

1. Define an acid and a base according to Bronsted-Lowry concept and justify with examples that water is an amphoteric compound.

  • According to the Bronsted-Lowry concept, an acid is a substance that donates protons (H⁺ ions), while a base is a substance that accepts protons.
  • Water (H₂O) is an amphoteric compound, meaning it can act both as an acid and as a base depending on the situation. For example:
  • As a base: When reacting with hydrochloric acid (HCl):

    HCl + H_2O → H3O^+ + Cl^-
  • As an acid: When reacting with ammonia (NH₃):

    NH3 + H_2O → NH4^+ + OH^-

    In both cases, water accepts or donates a proton, demonstrating its amphoteric nature.

2. Explain the Lewis concept of acids and bases.

  • According to the Lewis concept, an acid is a substance that accepts an electron pair, while a base is a substance that donates an electron pair.
  • Lewis acid: Example – Aluminum chloride (AlCl₃) accepts an electron pair from chloride ions.
  • Lewis base: Example – Ammonia (NH₃) donates an electron pair to form a bond with hydrogen ions (H⁺).

3. What is auto-ionization of water? How is it used to establish the pH of water?

  • Auto-ionization of water refers to the process where water molecules react with each other to produce hydronium ions (H₃O⁺) and hydroxide ions (OH⁻):

    2H2O(l) ⇌ H3O^+(aq) + OH^-(aq)
  • The equilibrium constant for this reaction is called the ionization constant of water (Kw), and at 25°C, Kw = (1.0 \times 10^{-14}). The pH of water is calculated from the concentration of ( H3O^+ ) ions, which is 1.0 × 10⁻⁷ M, giving water a pH of 7 (neutral).

4. Define a salt and give the characteristic properties of salts.

  • A salt is an ionic compound formed when an acid reacts with a base, usually through neutralization. It is made up of positive ions (cations) from the base and negative ions (anions) from the acid.
  • Properties:
  • They are typically solid and crystalline.
  • Many salts are soluble in water.
  • Salts have high melting and boiling points.
  • In solution, salts can conduct electricity due to ion dissociation.

5. Explain with examples how are soluble salts prepared?

  • Soluble salts are typically prepared by reacting an acid with a base or by combining a metal with an acid.
  • Neutralization reaction: Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl), a soluble salt.

    HCl + NaOH → NaCl + H_2O
  • Reaction of metal with acid: Zinc reacts with sulfuric acid to form zinc sulfate (ZnSO₄), which is soluble in water.

    Zn + H2SO4 → ZnSO4 + H2

6. Give the characteristics of an acidic salt.

  • Acidic salts are formed by the partial neutralization of a polybasic acid with a base. These salts contain replaceable hydrogen ions (H⁺).
  • They react with bases to form normal salts.
  • They can release protons (H⁺) in solution, making the solution acidic.
  • Example: Sodium bisulfate (NaHSO₄) is an acidic salt because it can release H⁺ ions in solution.

7. Give four uses of calcium oxide.

  • Calcium oxide (quicklime) is used in various industries:
  1. Construction: It is used to make cement and mortar.
  2. Water treatment: It is used to remove impurities from water.
  3. Steel manufacturing: Used in the purification of steel.
  4. Soil treatment: It is used to neutralize acidic soils.

8. You are having a strong acid (HNO₃) and strong base (NaOH) on mixing:
i. What type of salt will you have?

  • The reaction between nitric acid (HNO₃) and sodium hydroxide (NaOH) will produce sodium nitrate (NaNO₃), which is a neutral salt. ii. What type of reaction will it be?
  • This is a neutralization reaction, where an acid and a base react to form water and a salt. iii. Will it be soluble or insoluble salt?
  • Sodium nitrate (NaNO₃) is a soluble salt. iv. If it is soluble, how will it be recovered?
  • Sodium nitrate can be recovered by evaporation of the water from the solution, leaving behind solid sodium nitrate crystals.

9. Explain why:
i. HCl forms only one series of salts.

  • Hydrochloric acid (HCl) is a monoprotic acid, meaning it has only one replaceable hydrogen ion, so it can only form one series of salts, like sodium chloride (NaCl). ii. H₂SO₄ forms two series of salts.
  • Sulfuric acid (H₂SO₄) is a diprotic acid with two replaceable hydrogen ions. It forms two types of salts:
    • Normal salts, e.g., sodium sulfate (Na₂SO₄), where both hydrogen ions are replaced.
    • Acidic salts, e.g., sodium bisulfate (NaHSO₄), where only one hydrogen ion is replaced.
    iii. H₃PO₄ forms three series of salts.
  • Phosphoric acid (H₃PO₄) is a triprotic acid, with three replaceable hydrogen ions, so it forms three types of salts:
    • Primary salts: NaH₂PO₄
    • Secondary salts: Na₂HPO₄
    • Tertiary salts: Na₃PO₄

10. Classify the following salts as soluble or insoluble salts:
i. Sodium chloride: Soluble
ii. Lead chloride: Insoluble
iii. Barium sulphate: Insoluble
iv. Sodium carbonate: Soluble
v. Silver nitrate: Soluble
vi. Copper sulphate: Soluble
vii. Ammonium chloride: Soluble
viii. Calcium carbonate: Insoluble
ix. Calcium chloride: Soluble
x. Magnesium sulphate: Soluble

11. Complete and balance the following equations:
i. Aluminium + Hydrochloric acid

2Al + 6HCl → 2AlCl3 + 3H2

ii. Copper oxide + Sulphuric acid

CuO + H_2SO_4 → CuSO_4 + H_2O

iii. Iron sulphide + Sulphuric acid

FeS + H2SO4 → FeSO4 + H2S

iv. Ammonium chloride + Sodium hydroxide

NH4Cl + NaOH → NH3 + NaCl + H_2O

v. Ferric chloride + Sodium hydroxide

FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl

Chemical Equilibrium 10th Exercise PTB

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Prepare for your 10th-grade exams with solved exercises on Chemical Equilibrium, following the PTB curriculum. Focus on concepts like Le Chatelier’s Principle, reaction rates, and equilibrium constants.

Short Questions:

1. What are irreversible reactions? Give a few characteristics of them?
Irreversible reactions are those in which reactants completely convert into products and cannot revert to their original form. Characteristics include:

  • The reaction proceeds in one direction.
  • The products do not revert to reactants.
  • The reaction often goes to completion.

2. Define chemical equilibrium state.
Chemical equilibrium is the state in a reversible reaction where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant over time.

3. Give the characteristics of reversible reactions.

  • Reversible reactions can proceed in both directions (forward and reverse).
  • At equilibrium, the concentrations of reactants and products become constant.
  • The reaction doesn’t stop; the forward and reverse rates are equal.

4. How is dynamic equilibrium established?
Dynamic equilibrium is established when the rate of the forward reaction becomes equal to the rate of the reverse reaction, and the concentrations of all reactants and products remain constant.

5. Why at equilibrium state reaction does not stop?
At equilibrium, the reaction doesn’t stop because both forward and reverse reactions continue at the same rate, resulting in no net change in concentrations.

6. Why is equilibrium state attainable from either way?
The equilibrium state is attainable from either side (reactants or products) because the system will adjust the rates of forward and reverse reactions to reach equilibrium, regardless of the starting conditions.

7. What is the relationship between active mass and rate of reaction?
The rate of a reaction is directly proportional to the active mass (concentration) of the reactants, as expressed in the law of mass action.

8. Derive equilibrium constant expression for the synthesis of ammonia from nitrogen and hydrogen.
For the reaction:
N2 + 3H2 ⇌ 2NH3
The equilibrium constant expression is:
Kc = [NH3]^2/[N2][H2]^3

9. Write the equilibrium constant expression for the following reactions:
i.

H2(g) + I2(g) ⇌ 2HI(g)

Kc = [HI]^2/[H2][I2]

ii.

CO(g) + 3H2(g) ⇌ CH4(g) + H2O(g)

Kc = [CH4][H2O]/[CO][H2]^3

10. How direction of a reaction can be predicted?
The direction of a reaction can be predicted by comparing the reaction quotient (Q) with the equilibrium constant (K).

  • If ( Q < K ), the reaction will proceed forward.
  • If ( Q > K ), the reaction will proceed in reverse.

11. How can you know that a reaction has achieved an equilibrium state?
A reaction has achieved equilibrium when the concentrations of reactants and products remain constant over time, and the rates of the forward and reverse reactions are equal.

12. What are the characteristics of a reaction that establishes equilibrium state at once?
Characteristics include:

  • Constant concentrations of reactants and products.
  • Equal rates for the forward and reverse reactions.
  • No observable changes in the system without external disturbance.
  • The reaction continues in both directions at equilibrium.

13. If reaction quotient Q, of a reaction is more than K, what will be the direction of the reaction?
If ( Q > K ), the reaction will shift in the reverse direction to re-establish equilibrium.

14. An industry was established based upon a reversible reaction. It failed to achieve products on a commercial level. Can you point out the basic reasons for its failure being a chemist?
Possible reasons for failure include:

  • Incorrect reaction conditions (e.g., temperature, pressure) that are not optimized for equilibrium.
  • The reaction not being conducted in a closed system, leading to loss of products.
  • Poor choice of catalyst, affecting the reaction rate or equilibrium.

Extensive Questions:

1. Describe a reversible reaction with the help of an example and graph.
A reversible reaction can proceed in both the forward and reverse directions. For example, the reaction ( N2 + 3H2 ⇌ 2NH3 ) is reversible. In this reaction, both the reactants (nitrogen and hydrogen) and products (ammonia) coexist at equilibrium. The graph shows that the concentration of reactants and products stabilizes as equilibrium is established, where both the forward and reverse reactions continue at the same rate.

2. Write down the macroscopic characteristics of dynamic equilibrium.
The macroscopic characteristics of dynamic equilibrium include:

  • Constant concentrations of reactants and products.
  • No observable changes in the system, even though reactions continue at the microscopic level.
  • Equal forward and reverse reaction rates.

3. State the law of Mass Action and derive the expression for equilibrium constant for a general reaction.
The law of Mass Action states that the rate of a reaction is proportional to the product of the concentrations of the reactants, each raised to the power of their respective stoichiometric coefficients. For a general reaction:

aA + bB ⇌ cC + dD

The equilibrium constant expression is:

Kc = [C]^c[D]^d/[A]^a[B]^b

4. What is the importance of equilibrium constant?
The equilibrium constant (K) provides valuable information about the position of equilibrium in a reaction. A large ( K ) value indicates that the reaction favors the formation of products, while a small ( K ) value indicates that reactants are favored. It helps chemists predict the concentrations of reactants and products at equilibrium and adjust reaction conditions accordingly.

Environmental Chemistry

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Enhance your understanding of Environmental Chemistry with comprehensive exercises and notes. Cover key topics like pollution, green chemistry, and sustainable practices to excel in exams and deepen your knowledge.

Q. 4 Discuss in detail the components of the environment.
The environment is composed of several key components:

  1. Atmosphere: The layer of gases surrounding Earth, including oxygen, nitrogen, carbon dioxide, and others. It protects life on Earth by blocking harmful solar radiation.
  2. Lithosphere: The solid outer part of the Earth, comprising rocks, soil, and minerals. It supports terrestrial ecosystems and human infrastructure.
  3. Hydrosphere: All the water on Earth’s surface, including oceans, rivers, lakes, and groundwater. It is crucial for life, as it supports aquatic ecosystems and is essential for human consumption.
  4. Biosphere: The global sum of all ecosystems, where living organisms interact with the other components of the environment. This includes all plants, animals, and microorganisms.

Q. 5 Describe the natural and human sources of carbon monoxide, nitrogen oxides, and sulphur oxides.

  • Carbon monoxide (CO):
  • Natural sources: Wildfires, volcanic eruptions, and the oxidation of methane in the atmosphere.
  • Human sources: Incomplete combustion of fossil fuels from vehicles, industrial processes, and residential heating.
  • Nitrogen oxides (NOx):
  • Natural sources: Lightning strikes, microbial activity in soils, and wildfires.
  • Human sources: Burning of fossil fuels in vehicles, power plants, and industrial activities.
  • Sulphur oxides (SOx):
  • Natural sources: Volcanic eruptions and the decomposition of organic matter.
  • Human sources: Burning of coal and oil, particularly in power plants and industrial processes like refining.

Q. 6 What is acid rain and how does it affect our environment?
Acid rain is rainfall that contains elevated levels of hydrogen ions (low pH) due to the presence of sulphuric and nitric acids, formed from sulfur dioxide (SO₂) and nitrogen oxides (NOx) emissions.
Effects on the environment:

  • Aquatic life: Acid rain lowers the pH of water bodies, harming fish and other aquatic organisms.
  • Soil: It leaches essential nutrients like calcium and magnesium from the soil, reducing soil fertility.
  • Vegetation: It damages the leaves of plants, stunts growth, and weakens trees, making them more vulnerable to diseases.
  • Built structures: Acid rain corrodes buildings, statues, and infrastructure, especially those made of limestone and marble.

Q. 7 What is smog? Explain the pollutants which are the main cause of photochemical smog.
Smog is a type of air pollution caused by the interaction of sunlight with pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs).

  • Photochemical smog: Formed when sunlight reacts with nitrogen oxides and hydrocarbons from vehicle emissions, creating harmful ozone (O₃) at ground level.
  • Main pollutants:
  • Nitrogen oxides (NOx): Emitted by vehicles and industrial processes.
  • Volatile organic compounds (VOCs): Released from vehicle exhaust, industrial emissions, and solvents.
  • Ozone (O₃): A secondary pollutant formed through the reaction of NOx and VOCs in sunlight, contributing to respiratory issues and environmental damage.

Q. 8 Why is the ozone layer depleting? What will happen when the concentration of ozone will be decreased?
The ozone layer is depleting due to the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS), which break down ozone molecules (O₃) in the stratosphere.

  • Consequences of ozone depletion:
  • Increased exposure to harmful ultraviolet (UV) radiation, leading to higher rates of skin cancer, cataracts, and immune system suppression in humans.
  • Disruption of marine ecosystems, particularly affecting plankton, which form the base of the aquatic food chain.
  • Harm to plant life, which could reduce agricultural productivity.

Q. 9 How is oil spillage affecting the marine life?
Oil spills cause significant harm to marine ecosystems:

  • Coating of animals: Oil coats the fur and feathers of marine animals such as birds and otters, reducing their insulation and buoyancy, leading to hypothermia or drowning.
  • Toxicity: The chemicals in oil are toxic to marine organisms, damaging their organs and reproductive systems.
  • Contamination of food chains: Oil contaminants enter the food chain, affecting not only marine organisms but also humans who consume seafood.

Q. 10 How detergents are a threat to aquatic animal life?
Detergents contain surfactants, phosphates, and other chemicals that can harm aquatic life:

  • Surfactants: Disrupt the membranes of aquatic organisms, leading to cell damage and death.
  • Phosphates: Promote eutrophication, leading to algal blooms that deplete oxygen in water, creating dead zones where aquatic life cannot survive.
  • Bioaccumulation: Some detergent chemicals accumulate in aquatic organisms, affecting their health and the health of those higher up the food chain.

Q. 12 Explain how pesticides are dangerous to human beings.
Pesticides are hazardous to humans through:

  • Acute toxicity: Exposure to high doses can cause immediate health issues such as nausea, dizziness, and respiratory problems.
  • Chronic exposure: Long-term exposure can lead to serious health effects, including cancer, neurological disorders, reproductive issues, and developmental problems in children.
  • Bioaccumulation: Pesticides can accumulate in the food chain, leading to higher concentrations in humans through consumption of contaminated food and water.

Q. 13 Discuss industrial waste effluents.
Industrial waste effluents are liquid waste products discharged by industries. They may contain:

  • Toxic chemicals: Such as heavy metals (lead, mercury), volatile organic compounds (VOCs), and acids, which can contaminate water sources and harm both human and environmental health.
  • Nutrients: Excess nitrogen and phosphorus from agricultural and food industries can cause eutrophication in water bodies.
  • Thermal pollution: Waste heat discharged into water bodies can disrupt ecosystems by altering temperature conditions and reducing oxygen levels.

Q. 14 How water is purified i.e., made potable. Discuss in detail.
Water purification involves several steps to remove contaminants and make it safe for drinking:

  1. Coagulation and flocculation: Chemicals (coagulants) are added to water to bind small particles into larger clumps (flocs).
  2. Sedimentation: The flocs settle at the bottom of a sedimentation tank.
  3. Filtration: The water passes through sand, gravel, or charcoal filters to remove smaller particles.
  4. Disinfection: Chlorine, ozone, or ultraviolet light is used to kill harmful bacteria, viruses, and parasites.
  5. Additional treatment: Fluoridation and pH adjustments may be done before distribution to consumers.

Q. 15 What are leachates?
Leachates are liquids that have percolated through solid waste (in landfills or contaminated soil) and extracted dissolved or suspended materials. Leachates often contain harmful chemicals and pollutants, which can contaminate soil and groundwater if not properly managed.

Q. 16 Explain the process of incineration of industrial waste.
Incineration is a waste treatment process that involves burning industrial waste at high temperatures (800°C to 1000°C). The waste is converted into ash, flue gases, and heat.
Steps involved in incineration:

  1. Waste preparation: Sorting and pre-treating waste materials to ensure safe combustion.
  2. Combustion: The waste is burned in a controlled environment, reducing the volume of solid waste by up to 90%.
  3. Energy recovery: The heat generated during incineration can be used to produce electricity or steam.
  4. Emission control: Pollutants in flue gases are treated using filters and scrubbers to minimize environmental harm.

Common Chemical Industries Solved Exercise PTB

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Prepare for second-year exams with solved exercises on Common Chemical Industries, based on the PTB curriculum. Cover essential topics such as industrial processes, applications, and key concepts to boost your understanding.

Q. 5 (a) What are fertilizers? Why are they needed?
Fertilizers are chemical or natural substances added to soil to supply essential nutrients to plants and promote growth. They are needed to replenish the soil with nutrients that are depleted due to continuous crop cultivation, ensuring high yields and healthy plant growth.

(b) Discuss the classification of fertilizers and their uses.
Fertilizers are classified into two main types:

  • Organic fertilizers: These come from natural sources such as manure, compost, and bone meal. They improve soil structure and water retention while providing nutrients.
  • Inorganic (chemical) fertilizers: These are synthesized to provide specific nutrients like nitrogen, phosphorus, and potassium (NPK).
  • Nitrogen fertilizers (e.g., urea): Promote leaf and stem growth.
  • Phosphorus fertilizers (e.g., superphosphate): Enhance root development and flowering.
  • Potassium fertilizers (e.g., potassium chloride): Improve overall plant health and disease resistance.

(c) How is urea manufactured in Pakistan? Describe in detail the process used.
Urea is synthesized from ammonia (NH₃) and carbon dioxide (CO₂) using the Bosch-Meiser process:

  1. Ammonia synthesis: Nitrogen is obtained from air, and hydrogen is derived from natural gas. These two gases react at high pressure and temperature in the presence of a catalyst to form ammonia.
    N₂ + 3H₂ → 2NH₃
  2. Urea synthesis: Ammonia reacts with carbon dioxide under high pressure to form ammonium carbamate, which is then dehydrated to form urea.
    2NH₃ + CO₂ → NH₂CONH₂ + H₂O
    The resulting urea is then prilled or granulated for use as fertilizer.

Q. 6 (a) What are the prospects of fertilizer industry in Pakistan?
The fertilizer industry in Pakistan has significant growth potential due to the country’s agrarian economy. Increasing demand for agricultural productivity, government subsidies, and rising export opportunities can further boost the industry. However, challenges include the high cost of raw materials and energy shortages.

(b) What are essential nutrient elements and why are these needed for plant growth?
Essential nutrient elements are chemical elements required for plants to grow and complete their life cycle. They are divided into macronutrients and micronutrients:

  • Macronutrients: Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulfur (S).
  • Micronutrients: Iron (Fe), Zinc (Zn), Manganese (Mn), Boron (B), Copper (Cu), Molybdenum (Mo), and Chlorine (Cl).
    These nutrients play vital roles in photosynthesis, respiration, enzyme activation, and overall plant health.

(c) Write down the essential qualities of a good fertilizer.
A good fertilizer should:

  • Contain the right proportion of essential nutrients.
  • Be easily absorbed by plants.
  • Be cost-effective and easy to apply.
  • Have minimal environmental impact (low toxicity).
  • Improve soil fertility over time without causing nutrient imbalance.

Q. 7 (a) Describe the composition of a good Portland cement.
Portland cement is composed of the following main ingredients:

  • Calcium oxide (CaO): 60-65%
  • Silica (SiO₂): 20-25%
  • Alumina (Al₂O₃): 5-10%
  • Iron oxide (Fe₂O₃): 2-4%
  • Magnesia (MgO): 1-3%
  • Sulfur trioxide (SO₃): 1-2%
    Additionally, small amounts of gypsum are added to control the setting time.

(b) Discuss the wet process for the manufacturing of cement with the help of flow sheet diagram.
In the wet process, the raw materials (limestone and clay) are ground with water to form a slurry. The steps include:

  1. Raw material preparation: Limestone and clay are crushed and mixed with water to form slurry.
  2. Mixing: The slurry is blended to achieve uniform composition.
  3. Heating in a kiln: The slurry is fed into a rotary kiln and heated to high temperatures (up to 1400-1500°C), resulting in clinker formation.
  4. Clinker cooling and grinding: The clinker is cooled, mixed with gypsum, and ground to produce cement.

(c) What do you understand by the term “setting of cement”? Also discuss the reactions taking place in the first 24 hours.
The “setting of cement” refers to the process by which the cement paste transforms from a fluid to a solid state upon hydration.

  • Initial setting: The hydration of tricalcium silicate (C₃S) and dicalcium silicate (C₂S) produces calcium silicate hydrate (C-S-H) and calcium hydroxide (Ca(OH)₂), resulting in the hardening of the cement.
  • Within 24 hours: The initial set occurs as C₃S reacts rapidly, contributing to early strength development, while C₂S reacts slowly, providing long-term strength.

Q. 8 What are the essential non-woody raw materials used in the production of pulp and paper in Pakistan?
The essential non-woody raw materials used in pulp and paper production in Pakistan include:

  • Wheat straw
  • Bagasse (sugarcane waste)
  • Rice straw
  • Kenaf (a fibrous plant)
    These materials are chosen for their availability and lower environmental impact compared to wood-based raw materials.

Q. 9 (a) What are the principal methods of chemical pulping used for the production of paper?
The principal methods of chemical pulping are:

  1. Kraft process (sulfate process): Wood chips are cooked in sodium hydroxide (NaOH) and sodium sulfide (Na₂S) to break down lignin and release cellulose fibers.
  2. Sulfite process: Uses sulfurous acid (H₂SO₃) and bisulfites to dissolve lignin.
  3. Soda process: Uses sodium hydroxide (NaOH) alone to separate fibers.

(b) Describe the neutral sulphite semi-chemical (NSSC) process for the manufacturing of pulp and paper.
In the NSSC process, wood chips are treated with sodium sulfite (Na₂SO₃) and sodium carbonate (Na₂CO₃) to partially break down lignin, followed by mechanical refining. This process produces a pulp with a balance between strength and quality, suitable for making corrugated boards and packaging material.

Q. 10 (a) What are the common bleaching agents used in the paper industry in Pakistan? Briefly describe the bleaching process.
Common bleaching agents used in the paper industry include:

  • Chlorine dioxide (ClO₂)
  • Hydrogen peroxide (H₂O₂)
  • Oxygen (O₂)
  • Ozone (O₃)

Bleaching process:
The bleaching process removes the residual lignin and brightens the pulp. It typically involves multiple stages:

  1. Lignin removal: Chlorine dioxide or oxygen is used to break down lignin.
  2. Brightening: Hydrogen peroxide or ozone is used to further whiten the pulp by oxidizing remaining chromophores.

(b) What are the prospects of the paper industry in Pakistan?
The paper industry in Pakistan has significant potential for growth due to the increasing demand for packaging and paper products. However, the industry faces challenges such as dependency on imported raw materials, lack of advanced technology, and environmental concerns related to deforestation. Development of non-wood raw materials and modernizing production processes can improve the industry’s prospects.

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