Class 10 Science (NCERT)

1. Burning of a magnesium ribbon in air is an example of which type of chemical reaction?

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

2. Which gas is evolved when dilute hydrochloric acid is added to reactive metals like zinc?

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

3. What is the chemical formula of rust formed on iron?

• A. FeO
• B. Fe₃O₄
• C. Fe₂O₃ · xH₂O
• D. Fe(OH)₃

4. The reaction in which a single reactant breaks down into two or more simpler products is called:

• A. Combination reaction
• B. Decomposition reaction
• C. Displacement reaction
• D. Neutralization reaction

5. Which of the following is an endothermic process?

• A. Respiration
• B. Decomposition of calcium carbonate
• C. Slaking of lime
• D. Combustion of methane

6. A substance that undergoes gain of oxygen or loss of hydrogen during a reaction is said to be:

• A. Reduced
• B. Oxidized
• C. Decomposed
• D. Neutralized

7. What is observed when lead nitrate powder is heated in a test tube?

• A. Yellow gas evolved
• B. Brown fumes of NO₂ evolved
• C. White precipitate formed
• D. Black residue left

8. Chemically, quick lime is known as:

• A. Calcium carbonate (CaCO₃)
• B. Calcium hydroxide (Ca(OH)₂)
• C. Calcium oxide (CaO)
• D. Calcium sulfate (CaSO₄)

9. When calcium oxide reacts vigorously with water, it produces slaked lime along with heat. This reaction is:

• A. Endothermic
• B. Exothermic
• C. Displacement
• D. Photochemical

10. The process of respiration in human beings is an example of an:

• A. Exothermic reaction
• B. Endothermic reaction
• C. Reduction reaction
• D. Displacement reaction

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

• A. 1 : 1
• B. 2 : 1
• C. 1 : 2
• D. 4 : 1

12. Silver chloride turns grey when exposed to sunlight due to:

• A. Thermal decomposition
• B. Photolytic decomposition
• C. Oxidation
• D. Displacement

13. Which chemical reaction is utilized in black and white photography?

• A. Decomposition of AgBr
• B. Combination of CaO and H₂O
• C. Displacement of Cu by Fe
• D. Oxidation of Fe

14. When iron nails are dipped in blue copper sulfate solution, the solution turns light green due to formation of:

• A. Fe₂O₃
• B. FeSO₄
• C. Cu(NO₃)₂
• D. FeCl₂

15. The reaction Fe₂O₃ + 2Al → Al₂O₃ + 2Fe is an example of a:

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

16. The chemical equation must be balanced to satisfy which fundamental law?

• A. Law of Definite Proportions
• B. Law of Conservation of Mass
• C. Law of Multiple Proportions
• D. Avogadro's Law

17. A reaction in which exchange of ions takes place between reactants is called:

• A. Displacement reaction
• B. Double displacement reaction
• C. Combination reaction
• D. Oxidation reaction

18. What is formed when sodium sulfate solution reacts with barium chloride solution?

• A. White precipitate of BaSO₄
• B. Yellow precipitate of BaSO₄
• C. Red precipitate of NaCl
• D. No precipitate

19. In the reaction CuO + H₂ → Cu + H₂O, which substance acts as the reducing agent?

• A. CuO
• B. H₂
• C. Cu
• D. H₂O

20. The shiny brown element 'X' on heating in air turns black and forms compound 'Y'. Name 'X' and 'Y'.

• A. X = Fe, Y = Fe₂O₃
• B. X = Cu, Y = CuO
• C. X = Mg, Y = MgO
• D. X = Ag, Y = Ag₂O

21. Prevention of oxidation of fat and oil-containing food items is achieved by adding:

• A. Oxidizing agents
• B. Antioxidants
• C. Catalysts
• D. Acids

22. Which gas is flushed into bags of potato chips to prevent rancidity?

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

23. The green coating formed on copper vessels when exposed to moist air is due to formation of:

• A. Copper carbonate
• B. Copper oxide
• C. Copper sulfate
• D. Copper hydroxide

24. Black coating on silver objects on exposure to air is due to the formation of:

• A. Silver nitrate
• B. Silver sulfide
• C. Silver oxide
• D. Silver carbonate

25. What type of reaction occurs when dilute hydrochloric acid is added to marble chips (calcium carbonate)?

• A. Evolution of CO₂ gas
• B. Evolution of H₂ gas
• C. Formation of green precipitate
• D. No reaction

26. Redux reactions involve simultaneous occurrence of:

• A. Oxidation and Neutralization
• B. Oxidation and Reduction
• C. Combination and Decomposition
• D. Corrosion and Rancidity

27. Which condition is necessary for photo-decomposition reactions?

• A. Electricity
• B. Heat
• C. Sunlight
• D. Catalyst

28. Which of the following is a physical change and NOT a chemical change?

• A. Ripening of fruits
• B. Souring of milk
• C. Melting of candle wax
• D. Digestion of food

29. What is the coefficient of O₂ in the balanced chemical equation: 2Mg + O₂ → 2MgO?

• A. 1
• B. 2
• C. 3
• D. 4

30. Any reaction that produces an insoluble solid in water is known as a:

• A. Precipitation reaction
• B. Neutralization reaction
• C. Oxidation reaction
• D. Thermal reaction