Class 10 Science – Chapter 1: Chemical Reactions and Equations
(GSEB/CBSE Board Exam Level)
1. Which of the following is NOT an indicator of a chemical reaction?
A) Change in colour
B) Evolution of gas
C) Change in shape only
D) Change in temperature
Answer: C
2. Magnesium ribbon is cleaned with sandpaper before burning because it:
A) Makes it shine
B) Removes the oxide layer
C) Makes it softer
D) Removes moisture
Answer: B
3. Magnesium burns in air to form:
A) Magnesium carbonate
B) Magnesium oxide
C) Magnesium hydroxide
D) Magnesium sulphate
Answer: B
4. Which law is followed while balancing chemical equations?
A) Law of Multiple Proportions
B) Law of Conservation of Mass
C) Avogadro's Law
D) Boyle's Law
Answer: B
5. Which of the following is a balanced chemical equation?
A) Mg + O₂ → MgO
B) 2Mg + O₂ → 2MgO
C) Mg + O → MgO
D) Mg₂ + O₂ → MgO
Answer: B
6. The symbol (aq) in a chemical equation represents:
A) Gas
B) Liquid
C) Solid
D) Aqueous solution
Answer: D
7. Which reaction is a combination reaction?
A) CaO + H₂O → Ca(OH)₂
B) CaCO₃ → CaO + CO₂
C) Fe + CuSO₄ → FeSO₄ + Cu
D) AgNO₃ + NaCl → AgCl + NaNO₃
Answer: A
8. The reaction between quicklime and water is:
A) Endothermic
B) Exothermic
C) Neutralisation
D) Redox
Answer: B
9. Which reaction is an example of thermal decomposition?
A) CaCO₃ → CaO + CO₂
B) Zn + CuSO₄ → ZnSO₄ + Cu
C) H₂ + Cl₂ → 2HCl
D) CaO + H₂O → Ca(OH)₂
Answer: A
10. Brown fumes are evolved when heating:
A) Copper sulphate
B) Lead nitrate
C) Sodium chloride
D) Calcium carbonate
Answer: B
11. The gas responsible for brown fumes during decomposition of lead nitrate is:
A) Oxygen
B) Nitrogen
C) Nitrogen dioxide
D) Sulphur dioxide
Answer: C
12. Silver chloride turns grey in sunlight because:
A) It melts
B) It decomposes into silver
C) It evaporates
D) It reacts with oxygen
Answer: B
13. Decomposition of water by electricity is called:
A) Combustion
B) Electrolysis
C) Neutralisation
D) Fermentation
Answer: B
14. During electrolysis of water, hydrogen and oxygen are obtained in the ratio:
A) 1 : 1
B) 1 : 2
C) 2 : 1
D) 3 : 1
Answer: C
15. Iron displaces copper from copper sulphate because iron is:
A) Less reactive
B) More reactive
C) Equal in reactivity
D) Non-metal
Answer: B
16. Which is a displacement reaction?
A) Fe + CuSO₄ → FeSO₄ + Cu
B) CaO + H₂O → Ca(OH)₂
C) CaCO₃ → CaO + CO₂
D) AgNO₃ + NaCl → AgCl + NaNO₃
Answer: A
17. A white precipitate is formed when sodium sulphate reacts with:
A) HCl
B) Barium chloride
C) Copper sulphate
D) Zinc sulphate
Answer: B
18. Double displacement reactions usually involve:
A) Heat evolution only
B) Exchange of ions
C) Exchange of electrons only
D) Formation of gases only
Answer: B
19. In the reaction CuO + H₂ → Cu + H₂O, CuO is:
A) Oxidised
B) Reduced
C) Neutralised
D) Displaced
Answer: B
20. Oxidation means:
A) Gain of oxygen
B) Loss of oxygen
C) Gain of hydrogen
D) Loss of electrons only
Answer: A
21. Rusting of iron is an example of:
A) Corrosion
B) Neutralisation
C) Decomposition
D) Fermentation
Answer: A
22. The green coating on copper is due to formation of:
A) Copper oxide
B) Copper sulphate
C) Basic copper carbonate
D) Copper chloride
Answer: C
23. Rancidity occurs due to:
A) Reduction of fats
B) Oxidation of fats and oils
C) Heating of oils
D) Fermentation
Answer: B
24. Nitrogen gas is filled in packets of chips to:
A) Increase taste
B) Increase weight
C) Prevent oxidation
D) Remove moisture
Answer: C
25. Which of the following is an example of an exothermic reaction?
A) Photosynthesis
B) Respiration
C) Electrolysis of water
D) Decomposition of calcium carbonate
Answer: B
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