Class 10 Science Quiz- Chapter 1:Chemical Reactions and Equations

 

Class 10 Science Quiz – Chapter 1: Chemical Reactions and Equations

1. Which of the following is a chemical change?

A. Melting of ice
B. Tearing of paper
C. Burning of wood
D. Breaking of glass

Answer: C. Burning of wood
Explanation: Burning is a chemical reaction as it produces new substances and heat.

2. What is the chemical formula of quick lime?

A. Ca(OH)₂
B. CaCO₃
C. CaO
D. CaCl₂

Answer: C. CaO
Explanation: Quick lime is chemically calcium oxide.

3. Which gas is evolved when dilute hydrochloric acid reacts with zinc?

A. Oxygen
B. Hydrogen
C. Carbon dioxide
D. Nitrogen

Answer: B. Hydrogen
Explanation: Zinc reacts with HCl to produce hydrogen gas.

4. What type of reaction is: Fe + CuSO₄ → FeSO₄ + Cu?

A. Combination reaction
B. Displacement reaction
C. Decomposition reaction
D. Double displacement reaction

Answer: B. Displacement reaction
Explanation: Iron displaces copper from its salt solution.

5. What is the colour of copper sulphate solution?

A. Green
B. Blue
C. Red
D. Yellow

Answer: B. Blue
Explanation: Copper sulphate solution is blue in color due to Cu²⁺ ions.

6. A reaction in which heat is released is known as:

A. Endothermic
B. Exothermic
C. Photochemical
D. Thermal decomposition

Answer: B. Exothermic
Explanation: Exothermic reactions release heat energy.

7. What type of reaction is the electrolysis of water?

A. Displacement
B. Combination
C. Decomposition
D. Redox

Answer: C. Decomposition
Explanation: Electrolysis splits water into hydrogen and oxygen, which is a decomposition reaction.

8. Which reaction is used in whitewashing walls?

A. Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
B. CaCO₃ + HCl → CaCl₂ + CO₂ + H₂O
C. CaO + H₂O → Ca(OH)₂
D. Both A and C

Answer: D. Both A and C
Explanation: Whitewashing involves formation of slaked lime and then hardening by absorbing CO₂.

9. What is observed when silver chloride is kept in sunlight?

A. It becomes white
B. It turns black
C. It becomes yellow
D. It does not change

Answer: B. It turns black
Explanation: Silver chloride decomposes in sunlight forming silver (black in color).

10. What does a balanced chemical equation satisfy?

A. Avogadro’s law
B. Law of conservation of mass
C. Newton’s third law
D. None of these

Answer: B. Law of conservation of mass
Explanation: Balanced equations ensure mass is conserved on both sides of the reaction.