CBSE – Grade 10 – Science – Ch 01 – QA

Questions & Answers

CBSE - Grade - 10

Subject: Science

Chapter - 01 - Chemical Reactions and Equations

Types of Questions

MCQ

  1. A chemical reaction involves:
    1. Breaking and making of bonds
    2. Only breaking of bonds
    3. Only making of bonds
    4. No bond changes
  2. Which of the following is NOT a sign of a chemical reaction?
    1. Change in color
    2. Evolution of gas
    3. Change in shape without a new substance
    4. Change in temperature
  3. What is the substance formed as a result of a chemical reaction called?
    1. Reactant
    2. Catalyst
    3. Product
    4. Element
  4. The equation Mg + O₂ → MgO is an example of:
    1. Balanced equation
    2. Unbalanced equation
    3. Displacement reaction
    4. Decomposition reaction
  5. Which law is followed when balancing a chemical equation?
    1. Law of Multiple Proportions
    2. Law of Conservation of Mass
    3. Law of Constant Composition
    4. Law of Gases
  6. What are the reactants in the reaction: Zn + H₂SO₄ → ZnSO₄ + H₂?
    1. Zn and H₂SO₄
    2. ZnSO₄ and H₂
    3. Only Zn
    4. Only H₂SO₄
  7. A reaction in which two or more substances combine to form a single product is called:
    1. Decomposition reaction
    2. Displacement reaction
    3. Combination reaction
    4. Redox reaction
  8. Identify the combination reaction:
    1. CaO + H₂O → Ca(OH)₂
    2. 2H₂O → 2H₂ + O₂
    3. Zn + CuSO₄ → ZnSO₄ + Cu
    4. AgBr → Ag + Br₂
  9. What happens when calcium oxide reacts with water?
    1. A gas is released
    2. A base is formed
    3. An acid is formed
    4. A metal is formed
  10. Which of the following is an exothermic reaction?
    1. CaCO₃ → CaO + CO₂
    2. C + O₂ → CO₂
    3. 2AgCl → 2Ag + Cl₂
    4. H₂O → H₂ + O₂
  11. Which of the following is a decomposition reaction?
    1. H₂ + Cl₂ → 2HCl
    2. CaCO₃ → CaO + CO₂
    3. NaCl + AgNO₃ → AgCl + NaNO₃
    4. CuSO₄ + Zn → ZnSO₄ + Cu
  12. The decomposition of silver chloride in sunlight is an example of:
    1. Thermal decomposition
    2. Electrolysis
    3. Photolysis
    4. Precipitation
  13. Electrolysis of water gives:
    1. Hydrogen and oxygen in a 1:1 ratio
    2. Hydrogen and oxygen in a 2:1 ratio
    3. Only hydrogen
    4. Only oxygen
  14. Which is an example of a displacement reaction?
    1. Fe + CuSO₄ → FeSO₄ + Cu
    2. NaOH + HCl → NaCl + H₂O
    3. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
    4. H₂O → H₂ + O₂
  15. In Fe + CuSO₄ → FeSO₄ + Cu, which element is displaced?
    1. Fe
    2. Cu
    3. SO₄
    4. None
  16. Which reaction is an example of a double displacement reaction?
    1. 2KBr + BaI₂ → 2KI + BaBr₂
    2. Zn + CuSO₄ → ZnSO₄ + Cu
    3. H₂ + Cl₂ → 2HCl
    4. CaCO₃ → CaO + CO₂
  17. In the reaction ZnO + C → Zn + CO, which substance is oxidized?
    1. ZnO
    2. Zn
    3. C
    4. CO
  18. Which of the following is a redox reaction?
    1. NaOH + HCl → NaCl + H₂O
    2. Mg + O₂ → MgO
    3. AgNO₃ + NaCl → AgCl + NaNO₃
    4. H₂O → H₂ + O₂
  19. The reaction CuO + H₂ → Cu + H₂O is an example of:
    1. Oxidation only
    2. Reduction only
    3. Redox reaction
    4. Precipitation reaction

Answer Key

  1. a)
  2. c)
  3. c)
  4. b)
  5. b)
  6. a)
  7. c)
  8. a)
  9. b)
  10. b)
  11. b)
  12. c)
  13. b)
  14. a)
  15. b)
  16. a)
  17. c)
  18. b)
  19. c)

Fill in the Blanks

  1. A chemical reaction involves the breaking of old ______ and the formation of new ones.
     (bonds)


  2. The representation of a chemical reaction using symbols and formulae is called a ______.
     (chemical equation)


  3. A reaction in which heat is released along with the formation of products is called an ______ reaction.
     (exothermic)


  4. The reaction in which oxygen is added to a substance or hydrogen is removed is known as ______.
     (oxidation)


  5. The reaction between an acid and a base to form salt and water is called a ______ reaction.
     (neutralization)


  6. The reaction in which one element replaces another in a compound is called a ______ reaction.
     (displacement)


  7. A reaction in which a single compound breaks down into two or more products is known as ______.
     (decomposition reaction)


  8. The rusting of iron is an example of a ______ reaction.
     (oxidation)


  9. The reaction in which two or more reactants combine to form a single product is called a ______ reaction.
     (combination reaction)


  10. The addition of oxygen to a substance is called ______, while the removal of oxygen is called ______.
     (oxidation, reduction)


  11. Burning of magnesium ribbon in air produces ______.
     (magnesium oxide – MgO)


  12. The chemical formula of quicklime is ______.
     (CaO – Calcium Oxide)


  13. When an iron nail is dipped in copper sulfate solution, the color of the solution changes from ______ to ______.
     (blue, green)


  14. A balanced chemical equation follows the law of ______.
     (conservation of mass)


  15. The reaction of calcium carbonate with hydrochloric acid produces ______ gas.
     (carbon dioxide – CO₂)


  16. The insoluble solid that separates out in a reaction is called a ______.
     (precipitate)


  17. Hydrogen gas is liberated when zinc reacts with ______.
     (dilute hydrochloric acid – HCl)


  18. The decomposition of a compound due to the passage of electric current is called ______.
     (electrolysis)


  19. The reaction between barium chloride and sodium sulfate forms an insoluble ______.
     (barium sulfate – BaSO₄)


  20. The chemical formula of washing soda is ______.
     (Na₂CO₃·10H₂O)


  21. The chemical formula of slaked lime is ______.
     (Ca(OH)₂ – Calcium Hydroxide)


  22. The reaction between an acid and a metal produces ______ gas.
     (hydrogen – H₂)


  23. Photosynthesis is an example of a ______ reaction.
     (endothermic reaction)


  24. The brownish layer formed on iron due to reaction with oxygen and moisture is called ______.
     (rust – Fe₂O₃·xH₂O)


  25. A reaction in which heat is absorbed from the surroundings is called an ______ reaction.
     (endothermic)


  26. The gas evolved when baking soda reacts with acetic acid is ______.
     (carbon dioxide – CO₂)


  27. A reaction in which two compounds exchange their ions to form new compounds is called a ______ reaction.
     (double displacement)


  28. The green coating that appears on copper over time is due to the formation of ______.
     (copper carbonate – CuCO₃)


  29. Corrosion of aluminum is prevented due to the formation of a protective layer of ______.
     (aluminum oxide – Al₂O₃)


  30. The products of thermal decomposition of calcium carbonate are ______ and ______.
     (calcium oxide – CaO, carbon dioxide – CO₂)


  31. The change in color of copper sulfate solution in the presence of iron is an example of a ______ reaction.
     (displacement reaction)


  32. ______ reactions help in extracting metals from their ores.
     (Reduction)


  33. The chemical formula of vinegar is ______.
     (CH₃COOH – Acetic Acid)


  34. When a solution of lead nitrate is mixed with potassium iodide, a ______ colored precipitate is formed.
     (yellow)


  35. Oxidation and reduction reactions occurring simultaneously are called ______ reactions.
     (redox reactions)


  36. The gas released when limestone is heated strongly is ______.
     (carbon dioxide – CO₂)


  37. The reaction of iron with moist air results in the formation of ______.
     (rust – Fe₂O₃·xH₂O)


  38. The decomposition of silver chloride in sunlight produces ______ metal and ______ gas.
     (silver – Ag, chlorine – Cl₂)


  39. The chemical name of baking soda is ______.
     (sodium bicarbonate – NaHCO₃)


  40. The process of depositing a layer of zinc on iron to prevent rusting is called ______.
     (galvanization)


  41. When carbon dioxide is passed through lime water, it turns ______ due to the formation of ______.
     (milky, calcium carbonate – CaCO₃)


  42. The chemical reaction that takes place in fireworks is an example of an ______ reaction.
     (exothermic)


  43. When silver articles are exposed to air, they turn black due to the formation of ______.
     (silver sulfide – Ag₂S)


  44. Respiration is an example of an ______ reaction.
     (exothermic)


  45. The chemical name of quicklime is ______.
     (calcium oxide – CaO)


  46. ______ is the reaction in which hydrogen gas reacts with oxygen to form water.
     (combination reaction)


  47. The color of copper sulfate solution changes when an iron nail is dipped into it due to the formation of ______.
     (iron sulfate – FeSO₄)


  48. The process of extracting pure metal from its oxide by heating it with carbon is called ______.
     (reduction reaction)


  49. The gas evolved when zinc reacts with sulfuric acid is ______.
     (hydrogen – H₂)


  50. A reaction in which an element or compound combines with oxygen to release heat and light is called ______.
     (combustion reaction)

Name the Following

  1. The reaction in which two or more reactants combine to form a single product.
     Answer: Combination reaction


  2. The type of reaction in which a compound breaks down into two or more simpler substances.
     Answer: Decomposition reaction


  3. The reaction in which one element displaces another element from its compound.
     Answer: Displacement reaction


  4. The reaction in which two compounds exchange their ions to form new compounds.
     Answer: Double displacement reaction


  5. A reaction in which heat is released along with the formation of products.
     Answer: Exothermic reaction


  6. A reaction in which heat is absorbed from the surroundings.
     Answer: Endothermic reaction


  7. The law that states that mass can neither be created nor destroyed in a chemical reaction.
     Answer: Law of Conservation of Mass


  8. The reaction in which an element or a compound gains oxygen.
     Answer: Oxidation reaction


  9. The reaction in which an element or a compound loses oxygen.
     Answer: Reduction reaction


  10. A reaction where oxidation and reduction occur simultaneously.
     Answer: Redox reaction


  11. The brownish coating formed on iron when it reacts with air and moisture.
     Answer: Rust


  12. The process in which a metal surface is protected from rusting by coating it with zinc.
     Answer: Galvanization


  13. The compound responsible for the greenish deposit on copper objects.
     Answer: Basic copper carbonate


  14. The reaction responsible for food spoilage due to oxidation of oils and fats.
     Answer: Rancidity


  15. The gas produced when zinc reacts with dilute hydrochloric acid.
     Answer: Hydrogen gas (H₂)


  16. The reaction used in black and white photography involving the decomposition of silver chloride.
     Answer: Photochemical decomposition reaction


  17. The gas evolved when lead nitrate is heated strongly.
     Answer: Nitrogen dioxide (NO₂)


  18. The reaction in which a white precipitate of silver chloride is formed.
     Answer: Precipitation reaction


  19. The white compound formed when calcium hydroxide reacts with carbon dioxide.
     Answer: Calcium carbonate (CaCO₃)


  20. The reaction in which electricity is used to decompose water into hydrogen and oxygen.
     Answer: Electrolysis of water


  21. The insoluble substance formed during a precipitation reaction.
     Answer: Precipitate


  22. The type of decomposition reaction where heat is used to break down a compound.
     Answer: Thermal decomposition reaction


  23. The gas formed when calcium carbonate is heated.
     Answer: Carbon dioxide (CO₂)


  24. The product formed when magnesium ribbon burns in air.
     Answer: Magnesium oxide (MgO)


  25. The catalyst used in the decomposition of hydrogen peroxide (H₂O₂).
     Answer: Manganese dioxide (MnO₂)


  26. The type of reaction where two different ions in two reactant compounds exchange places.
     Answer: Double displacement reaction


  27. The reaction in which iron replaces copper from copper sulfate solution.
     Answer: Displacement reaction


  28. The type of reaction used in photosynthesis.
     Answer: Endothermic reaction


  29. The black powder formed when copper metal is heated in air.
     Answer: Copper (II) oxide (CuO)


  30. The reaction used for manufacturing cement where limestone is decomposed.
     Answer: Thermal decomposition of calcium carbonate


  31. The process in which food items containing oils and fats develop an unpleasant smell due to oxidation.
     Answer: Rancidity


  32. The reaction between zinc and hydrochloric acid is an example of which type of reaction?
     Answer: Displacement reaction


  33. The process of coating iron objects with a layer of zinc to prevent rusting.
     Answer: Galvanization


  34. The insoluble white solid formed when barium chloride reacts with sodium sulfate.
     Answer: Barium sulfate (BaSO₄)


  35. The gas produced when calcium carbonate reacts with dilute hydrochloric acid.
     Answer: Carbon dioxide (CO₂)


  36. The yellowish-brown gas evolved when lead nitrate is strongly heated.
     Answer: Nitrogen dioxide (NO₂)


  37. The greenish compound formed on iron when it reacts with moist air.
     Answer: Hydrated iron (III) oxide or Rust


  38. The chemical name of quicklime.
     Answer: Calcium oxide (CaO)


  39. The chemical reaction that causes silver jewelry to turn black over time.
     Answer: Formation of silver sulfide (Ag₂S) due to reaction with sulfur in the air


  40. The reaction in which sodium hydroxide reacts with hydrochloric acid to form salt and water.
     Answer: Neutralization reaction

Answer in One Word

  1. What is the reaction in which two or more substances combine to form a single product?
     Answer: Combination


  2. What is the reaction in which a compound breaks down into simpler substances?
     Answer: Decomposition


  3. What type of reaction involves the exchange of ions between reactants?
     Answer: Double displacement


  4. What type of reaction occurs when an element replaces another in a compound?
     Answer: Displacement


  5. What type of reaction occurs when heat is released?
     Answer: Exothermic


  6. What type of reaction occurs when heat is absorbed?
     Answer: Endothermic


  7. What is the process in which iron reacts with oxygen and water to form rust?
     Answer: Corrosion


  8. What is the reaction in which oxidation and reduction occur together?
     Answer: Redox


  9. What is the insoluble solid formed in a precipitation reaction called?
     Answer: Precipitate


  10. Which law states that mass is conserved in a chemical reaction?
     Answer: Conservation


  11. What is the chemical formula of rust?
     Answer: Fe₂O₃·xH₂O


  12. What is the reaction responsible for the blackening of silver articles?
     Answer: Oxidation


  13. Which process prevents rusting by coating iron with zinc?
     Answer: Galvanization


  14. Which gas is produced when zinc reacts with hydrochloric acid?
     Answer: Hydrogen


  15. Which gas is released when limestone (CaCO₃) is heated?
     Answer: Carbon dioxide


  16. Which reaction produces a white precipitate of silver chloride?
     Answer: Precipitation


  17. What is the color of copper sulfate solution?
     Answer: Blue


  18. What is the catalyst used in the decomposition of hydrogen peroxide?
     Answer: Manganese dioxide


  19. Which reaction requires sunlight for decomposition?
     Answer: Photochemical


  20. Which compound is formed when quicklime reacts with water?
     Answer: Slaked lime


  21. Which gas is evolved when lead nitrate is strongly heated?
     Answer: Nitrogen dioxide


  22. Which compound is used in whitewashing walls?
     Answer: Calcium hydroxide


  23. What is the reaction in which a more reactive metal replaces a less reactive one?
     Answer: Displacement


  24. What is the process of slow oxidation of fats and oils leading to spoilage?
     Answer: Rancidity


  25. What is the color of silver chloride?
     Answer: White


  26. What is the color of silver bromide?
     Answer: Yellow


  27. What is the chemical name of quicklime?
     Answer: Calcium oxide


  28. What is the chemical formula of slaked lime?
     Answer: Ca(OH)₂


  29. Which acid is present in gastric juice?
     Answer: Hydrochloric


  30. Which metal is commonly used to prevent rusting of iron?
     Answer: Zinc


  31. What is the process in which electricity is used to break down a compound?
     Answer: Electrolysis


  32. What is the chemical formula of water?
     Answer: H₂O


  33. Which gas is produced when calcium carbonate reacts with acid?
     Answer: Carbon dioxide


  34. What is the name of the process by which plants make their own food?
     Answer: Photosynthesis


  35. Which type of reaction occurs in a blast furnace to extract iron?
     Answer: Reduction


  36. Which metal does not corrode easily?
     Answer: Gold


  37. What is the product formed when magnesium ribbon burns in air?
     Answer: Magnesium oxide


  38. What is the name of the process used to remove impurities from metals?
     Answer: Refining


  39. Which chemical compound is used in black and white photography?
     Answer: Silver bromide


  40. What is the solid product formed in a neutralization reaction?
     Answer: Salt

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Find the Odd Man Out

Instructions: Identify the term that does NOT belong to the group.

  1. Zn, Fe, Cu, Ag

    (Answer: Ag – Least reactive metal)

  2. CaCO₃, NaCl, BaCl₂, AgNO₃

    (Answer: CaCO₃ – It is not a salt of a strong acid and strong base)

  3. H₂O, CO₂, O₂, N₂

    (Answer: H₂O – It is a liquid, others are gases)

  4. Na, K, Mg, Al

    (Answer: Al – It is not an alkali metal)

  5. HCl, H₂SO₄, NaOH, HNO₃

    (Answer: NaOH – It is a base, others are acids)

  6. CuSO₄, FeSO₄, AgNO₃, NaCl

    (Answer: NaCl – It is a neutral salt, others are colored salts)

  7. MgO, CO₂, SO₂, NO₂

    (Answer: MgO – It is a basic oxide, others are acidic oxides)

  8. ZnO, Fe₂O₃, CuO, Na₂O

    (Answer: Na₂O – It is a basic oxide, others are amphoteric or acidic oxides)

  9. Ca(OH)₂, NaOH, KOH, HCl

    (Answer: HCl – It is an acid, others are bases)

  10. Photosynthesis, Respiration, Burning, Rusting

    (Answer: Photosynthesis – It is an endothermic process, others are exothermic)

  11. Zn, Cu, Pb, Ag

    (Answer: Ag – It is a least reactive metal)

  12. CaO, MgO, K₂O, CO₂

    (Answer: CO₂ – It is an acidic oxide, others are basic oxides)

  13. Rusting, Galvanization, Painting, Oiling

    (Answer: Rusting – It is a corrosion process, others prevent corrosion)

  14. ZnSO₄, FeSO₄, MgSO₄, CuSO₄

    (Answer: CuSO₄ – It is blue in color, others are colorless or green)

  15. Mg + O₂, CaO + H₂O, NaCl + AgNO₃, Zn + CuSO₄

    (Answer: NaCl + AgNO₃ – It is a double displacement reaction, others are different types)

  16. H₂O, NH₃, CH₄, CO₂

    (Answer: CO₂ – It is not a covalent compound like others)

  17. Rusting, Photosynthesis, Electrolysis, Fermentation

    (Answer: Rusting – It is not a biological process)

  18. BaCl₂, Na₂SO₄, AgNO₃, NaOH

    (Answer: NaOH – It is a base, others participate in double displacement reactions)

  19. H₂, O₂, CO₂, N₂

    (Answer: CO₂ – It is not a diatomic molecule)

  20. Displacement, Combination, Decomposition, Photosynthesis

    (Answer: Photosynthesis – It is a biological process, others are chemical reactions)

Match the Pair

Short Answer Questions  

  1. What is a chemical reaction?
     Answer: A process in which reactants undergo a chemical change to form new substances called products.


  2. Why should a chemical equation be balanced?
     Answer: To satisfy the Law of Conservation of Mass, which states that mass cannot be created or destroyed.


  3. What are reactants and products in a chemical reaction?
     Answer: Reactants take part in a chemical reaction, while products are the substances formed.


  4. What is a skeletal chemical equation?
     Answer: An unbalanced equation where the number of atoms of each element is not the same on both sides.


  5. Write the balanced chemical equation for the reaction between hydrogen and oxygen to form water.
     Answer: .

  6. Define combination reaction with an example.
    Answer: A reaction where two or more reactants combine to form a single product.


  7. What is a decomposition reaction? Give an example.
    Answer: A reaction where a compound breaks into simpler substances. Example: .


  8. What is a displacement reaction? Give an example.
    Answer: A reaction in which a more reactive element replaces a less reactive one. 


  9. Define double displacement reaction with an example.
    Answer: A reaction in which two compounds exchange their ions. Example: .


  10. What is a precipitation reaction?
     Answer: A reaction in which an insoluble solid (precipitate) is formed. Example: .

  11. What is an exothermic reaction? Give an example.
    Answer: A reaction that releases heat. Example: .


  12. What is an endothermic reaction? Give an example.
    Answer: A reaction that absorbs heat. Example: Photosynthesis .


  13. Why is respiration considered an exothermic reaction?
    Answer: It releases energy in the form of ATP when glucose reacts with oxygen.


  14. Give an example of a reaction where heat is absorbed.
    Answer: The decomposition of calcium carbonate: .


  15. Why do decomposition reactions require energy?
     Answer: To break bonds in a compound, requiring heat, light, or electricity.

  16. Define oxidation with an example.
    Answer: The gain of oxygen or loss of hydrogen. Example: .


  17. Define reduction with an example.
    Answer: The gain of hydrogen or loss of oxygen. Example: .


  18. What is a redox reaction?
    Answer: A reaction where oxidation and reduction occur simultaneously.


  19. What happens when iron reacts with oxygen and water?
    Answer: It forms rust: .


  20. What is the role of hydrogen in the reaction ?
     Answer: Hydrogen acts as a reducing agent.


  21. What is corrosion?
    Answer: The gradual destruction of metals due to reactions with air, water, or chemicals.


  22. Why does iron rust?
    Answer: Iron reacts with oxygen and moisture, forming hydrated iron(III) oxide.


  23. What is galvanization?
    Answer: Coating iron with zinc to prevent rusting.


  24. What is rancidity?
    Answer: Oxidation of fats and oils in food, causing a bad taste and smell.


  25. How can rancidity be prevented?
     Answer: By adding antioxidants, storing food in airtight containers, or flushing with nitrogen gas.

  26. What is a catalyst?
    Answer: A substance that speeds up a reaction without being consumed.


  27. Give an example of a photochemical reaction.
    Answer: The decomposition of silver chloride in sunlight: .


  28. What is quicklime?
    Answer: Calcium oxide ().


  29. What happens when calcium hydroxide reacts with carbon dioxide?
    Answer: It forms calcium carbonate: .


  30. Why does silver turn black over time?
    Answer: Due to the formation of silver sulfide () from reaction with sulfur in air.


  31. Why do oil packets contain nitrogen gas?
    Answer: To prevent oxidation and rancidity.


  32. What is the chemical formula of slaked lime?
    Answer: .


  33. What is the color of copper sulfate solution?
    Answer:


  34. What happens when lead nitrate is heated?
    Answer: It decomposes to form lead oxide, nitrogen dioxide, and oxygen.


  35. Which gas is produced in electrolysis of water?
    Answer: Hydrogen and oxygen.


  36. What is the color of rust?
    Answer: Reddish-brown.


  37. What type of reaction is the thermite reaction?
    Answer: A redox reaction.


  38. What is the main product of the Haber process?
    Answer:


  39. Which metal does not corrode easily?
    Answer:


  40. What type of reaction is neutralization?
     Answer: A double displacement reaction.

Puzzles

Difference Between:

Assertion and Reason

True or False

  1. A chemical reaction always results in a change in state. (False)
  2. The formation of water from hydrogen and oxygen is a combination reaction. (True)
  3. In a balanced chemical equation, the number of atoms of each element on both sides must be equal. (True)
  4. Decomposition reactions always require heat energy. (False)
  5. Oxidation is the loss of oxygen from a substance. (False)
  6. A catalyst is a substance that slows down a chemical reaction. (False)
  7. Rusting of iron is an example of oxidation. (True)
  8. When silver chloride is exposed to sunlight, it decomposes into silver and chlorine gas. (True)
  9. Burning of coal is an exothermic reaction. (True)
  10. Photosynthesis is an exothermic reaction. (False)
  11. In a displacement reaction, a less reactive element replaces a more reactive one. (False)
  12. Double displacement reactions involve the exchange of ions between two compounds. (True)
  13. Electrolysis of water gives hydrogen and oxygen in a 1:1 ratio. (False)
  14. In the reaction Fe + CuSO₄ → FeSO₄ + Cu, iron is reduced. (False)
  15. Calcium hydroxide reacts with carbon dioxide to form calcium carbonate. (True)
  16. The reaction between sodium hydroxide and hydrochloric acid produces a gas. (False)
  17. Lead nitrate decomposes upon heating to give brown fumes of nitrogen dioxide. (True)
  18. Zinc can displace copper from copper sulfate solution. (True)
  19. Redox reactions involve both oxidation and reduction simultaneously. (True)
  20. Precipitation reactions always produce gases. (False)
  21. The reaction Zn + H₂SO₄ → ZnSO₄ + H₂ is a double displacement reaction. (False)
  22. Sulfur dioxide is responsible for acid rain. (True)
  23. Corrosion of iron is accelerated in the presence of salt and moisture. (True)
  24. The decomposition of water by electricity is called photolysis. (False)
  25. The reaction CuO + H₂ → Cu + H₂O is a redox reaction. (True)
  26. The reaction AgNO₃ + NaCl → AgCl + NaNO₃ is a precipitation reaction. (True)
  27. A change in color always indicates a chemical reaction. (False)
  28. Oxidation and reduction can occur independently. (False)
  29. Carbon dioxide is always released in decomposition reactions. (False)
  30. The burning of magnesium ribbon in air is an endothermic reaction. (False)
  31. A combination reaction results in the formation of two or more products. (False)
  32. The green coating on copper is due to the formation of basic copper carbonate. (True)
  33. Hydrogen gas is produced when aluminum reacts with dilute hydrochloric acid. (True)
  34. Rancidity occurs due to the oxidation of oils and fats. (True)
  35. The process of whitewashing walls involves the use of slaked lime. (True)
  36. Rusting of iron can be prevented by galvanization. (True)
  37. Precipitation reactions are a type of decomposition reaction. (False)
  38. The reaction Zn + CuSO₄ → ZnSO₄ + Cu is an example of a combination reaction. (False)
  39. A chemical equation must be balanced to follow the law of conservation of mass. (True)
  40. Respiration in living beings is an exothermic reaction. (True)

Long Answer Questions

1. Combination Reactions

1.1 Reaction of Magnesium with Oxygen

2Mg + O₂ → 2MgO


1.2 Formation of Slaked Lime (Calcium Hydroxide) from Quick Lime

CaO + H₂O → Ca(OH)₂

1.3 Carbon Burning in Oxygen

C + O₂ → CO₂

1.4 Hydrogen Combines with Oxygen to Form Water

2H₂ + O₂ → 2H₂O



2. Decomposition Reactions

2.1 Thermal Decomposition of Ferrous Sulphate

2FeSO₄ → Fe₂O₃ + SO₂ + SO₃


2.2 Thermal Decomposition of Calcium Carbonate (Limestone)

CaCO₃ → CaO + CO₂


2.3 Electrolysis of Water

2H₂O → 2H₂ + O₂


2.4 Decomposition of Lead Nitrate

2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂


3. Displacement Reactions


3.1 Iron Displaces Copper from Copper Sulphate Solution

Fe + CuSO₄ → FeSO₄ + Cu


3.2 Zinc Displaces Copper from Copper Sulphate Solution

Zn + CuSO₄ → ZnSO₄ + Cu


4. Double Displacement Reactions


4.1 Reaction of Sodium Sulphate with Barium Chloride

Na₂SO₄ + BaCl₂ → BaSO₄ ↓ + 2NaCl


5. Oxidation and Reduction (Redox Reactions)


5.1 Oxidation of Copper to Copper Oxide

2Cu + O₂ → 2CuO


5.2 Reduction of Copper Oxide with Hydrogen

CuO + H₂ → Cu + H₂O


5.3 Burning of Methane (Combustion Reaction)

CH₄ + 2O₂ → CO₂ + 2H₂O


6. Corrosion Reaction (Rusting of Iron)

4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃
 (This further dehydrates to form rust: Fe₂O₃·xH₂O)

 

Give Reasons

Arrange the Words 

Case Studies

Numericals

Numeric problems are not available for this chapter.

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