10th class

Chemical Industries Exercise Punjab Text Book

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Prepare for exams with exercises on Chemical Industries, tailored to the PTB curriculum. Focus on key concepts, industrial processes, and applications to reinforce your understanding.

Short Questions (Extended Answers)

  1. What role is played by pine oil in the froth flotation process?
    Pine oil acts as a frothing agent in the froth flotation process, which is used to separate hydrophobic materials from hydrophilic ones. It helps create a stable froth on the surface of the flotation cell, allowing valuable minerals, which are hydrophobic, to attach to air bubbles and rise to the surface for collection while the waste material (gangue) settles at the bottom.
  2. Name the various metallurgical operations.
    Metallurgical operations include:
  • Crushing and grinding: Reducing the size of ore particles.
  • Concentration or beneficiation: Removing impurities from the ore (e.g., froth flotation).
  • Roasting and calcination: Heating ore to remove volatile impurities.
  • Reduction: Extracting metals from their oxides using reducing agents.
  • Refining: Purifying the extracted metal.
  1. How is roasting carried out?
    Roasting involves heating sulfide ores in the presence of oxygen, converting them into oxides. For example, roasting zinc sulfide (ZnS) in air converts it to zinc oxide (ZnO) and sulfur dioxide (SO2). The process also helps in removing moisture and organic matter from the ore.
  2. Explain the process of electrorefining.
    Electrorefining is the purification of metals using an electrolytic cell. The impure metal is used as the anode, while a pure metal sheet serves as the cathode. When an electric current passes through the electrolyte, the pure metal dissolves from the anode and deposits onto the cathode, while impurities either dissolve in the electrolyte or form a sludge.
  3. What are the advantages of the Solvay process?
    The Solvay process, used to produce sodium carbonate (Na2CO3), has several advantages:
  • Uses inexpensive and readily available raw materials (salt and limestone).
  • Does not produce harmful by-products.
  • The ammonia used in the process is recycled, reducing waste.
  1. What is the principle of the Solvay process?
    The Solvay process relies on the reaction of sodium chloride (brine) with carbon dioxide and ammonia to form sodium bicarbonate, which is then heated to produce sodium carbonate. The overall reactions are designed to recycle ammonia and minimize waste.
  2. What happens when ammoniacal brine is carbonated?
    When carbon dioxide is bubbled through ammoniacal brine (a solution of ammonia and sodium chloride), sodium bicarbonate (NaHCO3) precipitates out. This occurs because sodium bicarbonate is less soluble in water, especially in the presence of ammonium chloride.
  3. How NaHCO3 is converted to Na2CO3?
    Sodium bicarbonate (NaHCO3) is heated during calcination to produce sodium carbonate (Na2CO3) and carbon dioxide (CO2). The reaction is:
    2 NaHCO3 → Na2CO3 + CO2 + H2O
  4. How is ammonia recovered in the Solvay’s process?
    Ammonia is recovered by treating the solution left after sodium bicarbonate precipitation with lime (calcium hydroxide). This releases ammonia gas, which can be recycled back into the process.
  5. How is ammonia prepared for the synthesis of urea?
    Ammonia is synthesized through the Haber process, where nitrogen and hydrogen gases are reacted under high pressure and temperature in the presence of an iron catalyst to form ammonia. The produced ammonia is then used as a feedstock for urea production.
  6. Describe the formation of petroleum.
    Petroleum is formed from the remains of ancient marine organisms that settled on the ocean floor millions of years ago. Under high pressure and heat, the organic matter decomposes anaerobically, transforming into hydrocarbons over time. These hydrocarbons migrate through porous rocks and accumulate in reservoir rocks.
  7. What is refining of petroleum, and how is it carried out?
    Refining of petroleum involves separating the complex mixture of hydrocarbons into useful fractions. This is done through fractional distillation, where crude oil is heated in a distillation column, and the different components are separated based on their boiling points.
  8. Give a use of kerosene oil.
    Kerosene is used as a fuel for jet engines, in heating systems, and for lighting lamps in areas without electricity.
  9. Describe the difference between diesel oil and fuel oil.
    Diesel oil is a light distillate used primarily as fuel for diesel engines, whereas fuel oil is a heavier fraction used in industrial boilers, ships, and power plants for heating and electricity generation.
  10. Write down the names of four fractions obtained by the fractional distillation of residual oil.
    Four fractions obtained are:
  • Lubricating oils
  • Paraffin wax
  • Asphalt
  • Heavy fuel oil
  1. What is the difference between crude oil and residual oil?
    Crude oil is the unrefined liquid extracted from the earth, containing a mixture of hydrocarbons. Residual oil is the leftover heavy fraction after the lighter hydrocarbons have been distilled off during refining.
  2. Which petroleum fraction is used in dry cleaning?
    Naphtha or light petroleum solvents are commonly used in dry cleaning due to their ability to dissolve grease and oils without damaging fabrics.

Extensive Questions (Detailed Answers)

  1. Describe in detail the various processes involved in the concentration of ore. Explain your answer with the help of diagrams.
    Concentration of ore involves several steps to increase the metal content:
  • Crushing and grinding: The ore is first broken into smaller pieces and then ground into a fine powder.
  • Gravity separation: Based on density differences, heavier metal particles are separated from lighter waste.
  • Froth flotation: For sulfide ores, the powdered ore is mixed with water and pine oil, then air is blown through the mixture, causing the metal-rich froth to float and be skimmed off.
  • Magnetic separation: This is used for magnetic ores, where magnetic fields attract the metal particles and separate them from the non-magnetic gangue.
  1. Explain the process of roasting with reference to copper.
    In the roasting of copper sulfide ore (e.g., Cu2S), the ore is heated in the presence of excess air. The sulfide is converted to oxide, and sulfur dioxide is released:
    2Cu2S + 3 O2 → 2Cu2O} + 2 SO2.
    This is followed by a reduction step to convert copper(I) oxide to metallic copper.
  2. Write a detailed note on the Solvay process.
    The Solvay process is used to manufacture sodium carbonate (soda ash). It involves the following steps:
  • Ammonia absorption: Ammonia gas is absorbed in brine (sodium chloride solution).
  • Carbonation: Carbon dioxide is bubbled through the ammoniacal brine, precipitating sodium bicarbonate.
  • Calcination: The sodium bicarbonate is heated to form sodium carbonate.
  • Ammonia recovery: The remaining solution is treated with lime to regenerate ammonia, which is recycled.
  1. Write a note on fractional distillation of petroleum.
    Fractional distillation is a method used to separate petroleum into various components based on their boiling points. Crude oil is heated in a distillation column, and as it rises, different fractions condense at various levels, such as:
  • Gasoline: Used as fuel for vehicles.
  • Kerosene: Used in jet engines and heating.
  • Diesel: Used in engines.
  • Heavy fuel oil: Used for ships and power generation.
  1. How urea is manufactured? Explain with a flow sheet diagram.
    Urea is manufactured by reacting ammonia and carbon dioxide under high pressure to form ammonium carbamate, which is then dehydrated to produce urea:
    2 NH3 + CO2 → NH2COONH4 → NH2CONH2 + H2O
    The process involves ammonia synthesis, carbon dioxide stripping, and urea synthesis sections.
  2. How crude oil is refined? Explain two important fractions of petroleum along with their usage.
    Crude oil is refined through fractional distillation. It is heated, and different components condense at different levels in the distillation column:
  • Gasoline: Used as fuel for cars and motorcycles.
  • Diesel oil: Used for powering heavy vehicles and machinery.
  1. Write a note in detail on smelting and bessemerization, giving a specific example.
  • Smelting: A process where metal ores are heated to high temperatures in the presence of a reducing agent, like carbon, to extract metals. For example, iron is extracted from its ore, hematite, by smelting in a blast furnace.
  • Bessemerization: It is a method of converting pig iron into steel by blowing air through the molten iron to remove impurities like carbon, silicon, and manganese. The process was crucial in

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

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