WORKSHEET – CHAPTER 1: CHEMICAL REACTIONS AND EQUATIONS

SECTION A – MULTIPLE CHOICE QUESTIONS (20 MCQs)

  1. The process in which new substances with new properties are formed is called:
     a) Physical change
     b) Chemical reaction
     c) Reversible change
     d) None

  2. Which of the following is a decomposition reaction?
     a) Zn + CuSO₄ → ZnSO₄ + Cu
     b) CaCO₃ → CaO + CO₂
     c) H₂ + Cl₂ → 2HCl
     d) 2Mg + O₂ → 2MgO

  3. The colour of copper sulphate solution changes when iron is added because:
     a) Iron is less reactive
     b) Iron displaces copper
     c) Copper dissolves iron
     d) Copper forms rust

  4. Which of the following is a photodecomposition reaction?
     a) 2AgCl → 2Ag + Cl₂
     b) CaCO₃ → CaO + CO₂
     c) 2H₂O → 2H₂ + O₂
     d) Fe + CuSO₄ → FeSO₄ + Cu

  5. Mass is conserved in a chemical reaction because:
     a) Atoms are destroyed
     b) Atoms are rearranged
     c) Atoms are created
     d) Energy is lost

  6. Rusting of iron is an example of:
     a) Reduction
     b) Displacement
     c) Oxidation
     d) Neutralisation

  7. Which gas is released when Zn reacts with dilute HCl?
     a) Oxygen
     b) Hydrogen
     c) Nitrogen
     d) Carbon dioxide

  8. The symbol “(aq)” represents:
     a) Gas
     b) Aqueous solution
     c) Solid
     d) Precipitate

  9. Formation of BaSO₄ as a white solid is an example of:
     a) Combination reaction
     b) Displacement reaction
     c) Double displacement reaction
     d) Oxidation reaction

  10. Rancidity occurs due to:
     a) Hydrogenation
     b) Oxidation of oils
     c) Corrosion
     d) Evaporation

  11. Green coating on copper is due to the formation of:
     a) CuO
     b) CuCO₃·Cu(OH)₂
     c) Cu₂O
     d) CuCl₂

  12. Which of the following is an endothermic reaction?
     a) Burning of fuel
     b) Respiration
     c) Photosynthesis
     d) Rusting of iron

  13. In a displacement reaction, a metal displaces another metal which is:
     a) Equally reactive
     b) Less reactive
     c) More reactive
     d) Noble

  14. 2Mg + O₂ → 2MgO represents a:
     a) Decomposition reaction
     b) Combination reaction
     c) Redox reaction
     d) Both (b) and (c)

  15. AgCl turns grey in sunlight because:
     a) AgCl absorbs moisture
     b) Ag metal is formed
     c) Cl₂ collects on surface
     d) Light removes water

  16. In oxidation reactions:
     a) Oxygen is removed
     b) Hydrogen is added
     c) Electron is lost
     d) Both (b) and (c)

  17. In the reaction Zn + 2HCl → ZnCl₂ + H₂, Zn undergoes:
     a) Oxidation
     b) Reduction
     c) Both
     d) None

  18. BaCl₂ + Na₂SO₄ → BaSO₄ + NaCl is a:
     a) Combination reaction
     b) Displacement reaction
     c) Double displacement reaction
     d) Neutralisation reaction

  19. Slaking of lime is represented by:
     a) CaO + H₂O → Ca(OH)₂
     b) CaCO₃ → CaO + CO₂
     c) 2AgCl → 2Ag + Cl₂
     d) Zn + CuSO₄ → ZnSO₄ + Cu

  20. Which change indicates that a chemical reaction has occurred?
     a) Dissolving salt
     b) Melting ice
     c) Change in colour
     d) Breaking glass

SECTION B – ASSERTION & REASON (10 Questions)

  1. A: Rusting is an oxidation reaction.
     R: During rusting, oxygen reacts with iron.

  2. A: AgCl turns grey in sunlight.
     R: Silver metal is formed due to decomposition.

  3. A: A balanced equation has equal atoms on both sides.
     R: Mass is conserved in chemical reactions.

  4. A: Zinc displaces copper from CuSO₄ solution.
     R: Zinc is more reactive than copper.

  5. A: BaSO₄ forms a white precipitate.
     R: BaSO₄ is insoluble in water.

  6. A: Rancidity spoils food.
     R: It is caused due to oxidation of fats.

  7. A: Photosynthesis is endothermic.
     R: Sunlight is absorbed in the process.

  8. A: Decomposition reactions require energy.
     R: Heat, light, or electricity is supplied.

  9. A: All double displacement reactions form precipitates.
     R: They involve exchange of ions.

  10. A: Heating CaCO₃ gives CaO and CO₂.
     R: This is thermal decomposition.

SECTION C – ONE-WORD / VERY SHORT ANSWERS (10)

  1. Define oxidation.
  2. Name the gas evolved with Zn + HCl.
  3. Example of photochemical decomposition.
  4. What is corrosion?
  5. Write formula of slaked lime.
  6. Colour of FeSO₄ crystals.
  7. What does (↑) indicate?
  8. Give an exothermic reaction.
  9. Colour change when Fe reacts with CuSO₄.
  10. Balance: Mg + O₂ → ?

SECTION D – SHORT ANSWER QUESTIONS (8)

  1. State four indicators of a chemical reaction.
  2. Why is AgCl stored in dark bottles?
  3. Explain oxidation and reduction with examples.
  4. What is rancidity? Give two prevention methods.
  5. Explain displacement reaction with two examples.
  6. Why should chemical equations be balanced?
  7. Describe corrosion and give two examples.
  8. Explain thermal decomposition with one example.

SECTION E – LONG ANSWER QUESTIONS (5)

  1. Explain the different types of chemical reactions with examples.
  2. Describe corrosion, its effects, and prevention methods.
  3. Explain decomposition reactions (thermal, photolytic, electrolytic) with examples.
  4. What are redox reactions? Explain with suitable examples.
  5. Discuss chemical reactions in daily life (whitewashing, respiration, digestion, photosynthesis).
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