Class 10 Chemical Reactions and Equations Worksheet

Q1. Which observation provides evidence that a chemical reaction has taken place?

• (a) A solid is cut into smaller pieces.
• (b) A liquid is transferred into another container.
• (c) A gas is evolved when two substances react.
• (d) Water freezes into ice.

Q2. Which set of coefficients correctly balances the equation below? __Al + __O₂ → __Al₂O₃

• (a) 2, 1, 1
• (b) 4, 3, 2
• (c) 2, 3, 1
• (d) 1, 1, 2

Q3. Which of the following is a decomposition reaction?

• (a) 2Mg + O₂ → 2MgO
• (b) Zn + CuSO₄ → ZnSO₄ + Cu
• (c) CaCO₃ → CaO + CO₂
• (d) HCl + NaOH → NaCl + H₂O

Q4. When an iron nail is placed in copper sulphate solution, which metal is deposited on the nail?

• (a) Zinc
• (b) Copper
• (c) Iron
• (d) Silver

Q5. Which statement correctly describes an exothermic reaction?

• (a) It always absorbs heat from its surroundings.
• (b) It releases energy to its surroundings.
• (c) It cannot involve a chemical change.
• (d) It always produces a precipitate.

Q6. In the reaction CuO + H₂ → Cu + H₂O which substance undergoes reduction?

• (a) Hydrogen
• (b) Copper
• (c) Copper oxide
• (d) Water

Q7. Assertion–Reason Question

Assertion (A): A chemical equation should be balanced.

Reason (R): Atoms are conserved during a chemical reaction.

Choose the correct option:

• (a) Both A and R are true, and R correctly explains A.
• (b) Both A and R are true, but R does not correctly explain A.
• (c) A is true, but R is false.
• (d) A is false, but R is true.

Q8. Which method helps prevent rancidity in packaged food containing fats and oils?

• (a) Exposing the food to sunlight
• (b) Keeping the packet open
• (c) Flushing the packet with nitrogen gas
• (d) Increasing its contact with air

Q9. Why is a magnesium ribbon cleaned before it is burnt in air? What visible change is observed when it burns?

Q10. Balance the following chemical equations:

(a) Na + H₂O → NaOH + H₂

(b) Al + HCl → AlCl₃ + H₂

Q11. Write balanced chemical equations with appropriate state symbols for:

(a) The reaction between aqueous barium chloride and aqueous sodium sulphate, producing insoluble barium sulphate.

(b) The neutralisation of aqueous sodium hydroxide with aqueous hydrochloric acid.

Q12. Distinguish between combination and decomposition reactions. Give one balanced chemical equation for each type.

Q13. Explain why respiration is considered an exothermic process. Write a balanced chemical equation representing the overall reaction.

Q14. What is a precipitation reaction? Illustrate your answer with a balanced chemical equation and identify the precipitate formed.

Q15. Balance the following equations and identify the type of reaction in each case:

(a) Fe + H₂O (steam) → Fe₃O₄ + H₂

(b) Pb(NO₃)₂ → PbO + NO₂ + O₂ (on heating)

(c) Mg + O₂ → MgO

Q16. Consider the reaction: Fe₂O₃ + 2Al → Al₂O₃ + 2Fe

(a) Name the type of reaction.

(b) Identify the substance that is oxidised.

(c) Identify the substance that is reduced.

Q17. A student heats blue copper sulphate crystals strongly in a dry test tube.

(a) State the colour change observed.

(b) Explain why this change occurs.

(c) What happens when water is added to the anhydrous product?

Q18. Answer the following questions about corrosion and rancidity:

(a) What is corrosion? Give one everyday example.

(b) State two conditions that promote rusting of iron.

(c) Mention one method of preventing rancidity in food.

Q21.

(a) Explain the law of conservation of mass and its importance in balancing chemical equations. (2)

(b) Balance the following skeletal equations using the smallest whole-number coefficients. (3)

(i) KClO₃ → KCl + O₂

(ii) Al + Fe₂O₃ → Al₂O₃ + Fe

(iii) C₃H₈ + O₂ → CO₂ + H₂O

Q22.

(a) Explain oxidation and reduction in terms of gain or loss of oxygen. (2)

(b) Study the reaction given below and answer the questions that follow. (3)

CuO + H₂ → Cu + H₂O

(i) Which substance is oxidised?

(ii) Which substance is reduced?

(iii) Explain why this reaction is called a redox reaction.