Top 29 Most Important MCQs on Chemical Reactions and Equations – Class 10 Science Chapter 1 | CBSE Class 10

Welcome to Edumaterial Scholar! This blog post on Chapter 1 – Chemical Reactions and Equations (Class 10 Science, CBSE) brings you a comprehensive set of MCQs that cover every line of the NCERT textbook. Whether you're preparing for your exams or revising at the last minute, these multiple-choice questions are designed to help you grasp key concepts quickly and effectively. With detailed explanations provided for each question, this resource will boost your confidence and ensure you're fully prepared for the exam.

1. Which one of the following does not happen during a chemical reaction?

(a) Breaking of old chemical bonds and formation of new chemical bonds

(b) Formation of new substances with entirely different properties

(c) Atoms of one element change into those of another element to form new products

(d) A rearrangement of atoms takes place to form new products

Answer: (c) Atoms of one element change into those of another element to form new products

Explanation: Atoms of one element never change into another; chemical reactions involve rearrangement, not transmutation.

Also See: Chemical Reactions and Equations Class 10 Notes | Easy Explanation & Examples

2. Which of the following statements about the given reaction are correct?

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

(i) Iron metal is getting oxidised

(ii) Water is getting reduced

(iii) Water is acting as a reducing agent

(iv) Water is acting as an oxidising agent

(a) (i), (ii), and (iii)

(b) (iii) and (iv)

(c) (i), (ii), and (iv)

(d) (ii) and (iv)

Answer: (c) (i), (ii), and (iv)

Explanation: Iron loses electrons (oxidised), water gains electrons (reduced), so water acts as an oxidising agent.

3. You are given a solution of lead nitrate. In order to obtain a yellow precipitate, you should mix with it a solution of:

(a) Potassium chloride

(b) Potassium nitride

(c) Potassium sulphide

(d) Potassium iodide

Answer: (d) Potassium iodide

Explanation: Lead nitrate reacts with potassium iodide to form yellow lead iodide precipitate.

4. The following reaction is an example of:

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g)

(i) Displacement reaction

(ii) Combination reaction

(iii) Redox reaction

(iv) Neutralisation reaction

(a) (i) and (iv)

(b) (ii) and (iii)

(c) (i) and (iii)

(d) (iii) and (iv)

Answer: (c) (i) and (iii)

Explanation: Oxidation and reduction both occur (redox), and atoms are displaced during reaction.

5. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is(are) true?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv)

Answer: (b) (ii) and (iii)

Explanation: Slaking of lime releases heat (exothermic) and forms a basic solution (pH > 7).

6. One of the following is an endothermic reaction. This is:

(a) Combination of carbon and oxygen to form carbon monoxide

(b) Combination of nitrogen and oxygen to form nitrogen monoxide

(c) Combination of glucose and oxygen to form carbon dioxide and water

(d) Combination of zinc and hydrochloric acid to form zinc chloride and hydrogen

Answer: (b) Combination of nitrogen and oxygen to form nitrogen monoxide

Explanation: The reaction between nitrogen and oxygen absorbs heat and is endothermic.

7. Which of the following is not an endothermic reaction?

(a) CaCO₃ → CaO + CO₂

(b) 2H₂O → 2H₂ + O₂

(c) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

(d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Answer: (d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Explanation: This is the respiration reaction and it releases energy, so it is exothermic.

8. One of the following is an exothermic reaction. This is:

(a) Electrolysis of water

(b) Conversion of limestone into quicklime

(c) Process of respiration

(d) Process of photosynthesis

Answer: (c) Process of respiration

Explanation: Respiration releases energy in the form of heat, making it an exothermic reaction.

9. Which of the following are exothermic processes?

(i) Reaction of water with quicklime

(ii) Dilution of an acid

(iii) Evaporation of water

(iv) Sublimation of camphor (crystals)

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) (iii) and (iv)

Answer: (a) (i) and (ii)

Explanation: Both the reaction of quicklime with water and acid dilution release heat.

10. The chemical equations are balanced to satisfy one of the following laws in chemical reactions. This law is known as:

(a) Law of conservation of momentum

(b) Law of conservation of mass

(c) Law of conservation of motion

(d) Law of conservation of magnetism

Answer: (b) Law of conservation of mass

Explanation: In a balanced equation, the total mass of reactants equals the mass of products.

11. Which of the following is not a physical change?

(a) Boiling of water to give water vapour

(b) Melting of ice to give water

(c) Dissolution of salt in water

(d) Combustion of Liquefied Petroleum Gas (LPG)

Answer: (d) Combustion of Liquefied Petroleum Gas (LPG)

Explanation: Combustion is a chemical reaction that produces new substances.

12. A dilute ferrous sulphate solution was gradually added to a beaker containing acidified permanganate solution. The purple colour disappears. Why?

(a) KMnO₄ is an oxidising agent, it oxidises FeSO₄

(b) FeSO₄ acts as an oxidising agent and oxidises KMnO₄

(c) The colour disappears due to dilution; no reaction is involved

(d) KMnO₄ is unstable and decomposes in the presence of FeSO₄

Answer: (a) KMnO₄ is an oxidising agent, it oxidises FeSO₄

Explanation: KMnO₄ oxidises ferrous ions to ferric ions and gets reduced, causing decolourisation.

13. Which among the following is(are) double displacement reaction(s)?

(i) Pb + CuCl₂ → PbCl₂ + Cu

(ii) Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl

(iii) C + O₂ → CO₂

(iv) CH₄ + 2O₂ → CO₂ + 2H₂O

(a) (i) and (iv)

(b) (ii) only

(c) (i) and (ii)

(d) (iii) and (iv)

Answer: (b) (ii) only

Explanation: Double displacement occurs in (ii) where two compounds exchange ions.

14. Which among the following statement(s) is(are) true? Exposure of silver chloride to sunlight turns it grey due to:

(i) Formation of silver by decomposition of silver chloride

(ii) Sublimation of silver chloride

(iii) Decomposition of chlorine gas from silver chloride

(iv) Oxidation of silver chloride

(a) (i) only

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (iv) only

Answer: (a) (i) only

Explanation: Sunlight causes silver chloride to decompose into silver, which appears grey.

15. Barium chloride reacts with ammonium sulphate to form barium sulphate and ammonium chloride. What type of reaction is this?

(a) Displacement reaction

(b) Precipitation reaction

(c) Double displacement reaction

(d) (b) and (c)

Answer: (d) (b) and (c)

Explanation: It is a double displacement reaction with formation of a white precipitate (BaSO₄).

Also See: Chemical Reactions and Equations Class 10 Notes | Easy Explanation & Examples

16. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated is:

(a) 1:1

(b) 2:1

(c) 4:1

(d) 1:2

Answer: (b) 2:1

Explanation: Two moles of hydrogen and one mole of oxygen are released in water electrolysis.

17. Which of the following is(are) endothermic processes?

(i) Dilution of sulphuric acid

(ii) Sublimation of dry ice

(iii) Condensation of water vapours

(iv) Evaporation of water

(a) (i) and (iii)

(b) (ii) only

(c) (iii) only

(d) (ii) and (iv)

Answer: (d) (ii) and (iv)

Explanation: Both sublimation and evaporation absorb heat from surroundings.

18. If lead nitrate is not available, which can be used to form yellow PbI₂ precipitate with potassium iodide?

(a) Lead sulphate

(b) Lead acetate

(c) Ammonium nitrate

(d) Potassium sulphate

Answer: (b) Lead acetate

Explanation: Lead acetate is soluble and will react with potassium iodide to form PbI₂.

19. Which acid can decolourise purple KMnO₄ solution?

(a) Sulphuric acid

(b) Citric acid

(c) Carbonic acid

(d) Hydrochloric acid

Answer: (d) Hydrochloric acid

Explanation: HCl reduces KMnO₄ and decolourises it by acting as a reducing agent.

20. Which of the following are combination reactions?

(i) 2KClO₃ → 2KCl + 3O₂

(ii) MgO + H₂O → Mg(OH)₂

(iii) 4Al + 3O₂ → 2Al₂O₃

(iv) Zn + FeSO₄ → ZnSO₄ + Fe

(a) (i) and (iii)

(b) (iii) and (iv)

(c) (ii) and (iv)

(d) (ii) and (iii)

Answer: (d) (ii) and (iii)

Explanation: Both are combination reactions where substances combine to form one product.

21. Which process involves a chemical reaction?

(a) Storing oxygen in a cylinder

(b) Liquefaction of air

(c) Keeping petrol open in a dish

(d) Heating copper wire in air at high temperature

Answer: (d) Heating copper wire in air at high temperature

Explanation: Copper reacts with oxygen to form copper oxide, a new substance.

22. Which equation shows correct physical states of substances at reaction temperature?

(a) 2H₂(l) + O₂(l) → 2H₂O(g)

(b) 2H₂(g) + O₂(l) → 2H₂O(l)

(c) 2H₂(g) + O₂(g) → 2H₂O(l)

(d) 2H₂(g) + O₂(g) → 2H₂O(g)

Answer: (d) 2H₂(g) + O₂(g) → 2H₂O(g)

Explanation: Hydrogen and oxygen are gases, and at high temperature, water is in vapour form.

Also See: Chemical Reactions and Equations Class 10 Notes | Easy Explanation & Examples

23. Three beakers A (NaOH), B (anhydrous CuSO₄), and C (NaCl) show different temperature changes. What is true?

(i) In A and B, an exothermic process occurred

(ii) In A and B, an endothermic process occurred

(iii) In C, an exothermic process occurred

(iv) In C, an endothermic process occurred

(a) (i) only

(b) (ii) only

(c) (i) and (iv)

(d) (ii) and (iii)

Answer: (c) (i) and (iv)

Explanation: NaOH and CuSO₄ dissolution release heat (exothermic); NaCl absorbs heat (endothermic).

24. The reaction 2KClO₃(s) → 2KCl(s) + 3O₂(g) is:

(a) A decomposition reaction and endothermic

(b) A combination reaction

(c) A decomposition reaction with heat release

(d) A photochemical decomposition and exothermic

Answer: (a) A decomposition reaction and endothermic

Explanation: Potassium chlorate breaks into simpler substances on heating, absorbing energy.

25. Why should magnesium ribbon be cleaned before burning in air?

A. To make it heavier

B. To remove the oxide layer for better combustion

C. To change its physical properties

D. To prevent it from melting quickly

Answer: B. To remove the oxide layer for better combustion

26. Why is photosynthesis considered an endothermic reaction?

A. It releases heat while making food

B. It absorbs sunlight to form glucose

C. It occurs only during the night

D. It produces carbon dioxide

Answer: B. It absorbs sunlight to form glucose

27. Translate and balance the following statement: Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.

A. BaCl₂ + ZnSO₄ → ZnCl₂ + BaSO₄ (Balanced)

B. BaCl₂ + ZnSO₄ → BaCl₂ + ZnSO₄ (Balanced)

C. BaCl₂ + ZnSO₄ → ZnCl₄ + BaSO₄ (Balanced)

D. BaCl₂ + Zn + SO₄ → ZnCl₂ + Ba + SO₄ (Balanced)

Answer: A. BaCl₂ + ZnSO₄ → ZnCl₂ + BaSO₄ (Balanced)

28. What happens when dilute hydrochloric acid is added to iron fillings?

(a) Hydrogen gas and iron chloride are produced.

(b) Chlorine gas and iron hydroxide are produced.

(c) No reaction takes place.

(d) Iron salt and water are produced.

Answer: (a) Hydrogen gas and iron chloride are produced.

29. What do you observe when barium hydroxide is mixed with ammonium chloride in a test tube and the bottom is touched with your palm?

(a) The test tube becomes warm; it is an exothermic reaction

(b) The test tube becomes cold; it is an exothermic reaction

(c) The test tube becomes cold; it is an endothermic reaction

(d) The test tube becomes warm; it is an endothermic reaction

Answer: (c) The test tube becomes cold; it is an endothermic reaction

Explanation: Heat is absorbed from the surroundings, making the test tube feel cold.