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CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class X > 2008 > Science > Science By :- Nagesh Kumar

Science - Chemical Reactions

  1. What happens when an iron nail is dipped in copper sulphate solution?
  2. Explain the oxidation in terms of gain or loss of oxygen with examples.
  3. Explain the terms oxidizing and reducing agents.
  4. Oil and fat containing food items are flushed with Nitrogen. Why?
  5. Why do we apply paint on iron articles?
  6. What do you understand by corrosion?
  7. Define oxidizing agent.
  8. Identify the component oxidized in the following reaction :    H2S  +  Cl2       →     S  +  2HCl
  9. Which of the following is a combination and which is a displacement reaction?  
    (a)      Cl2   +   2KI   →    2KCl   +   I2
  10. (b)      2K   +   Cl2     →   2KCl   

  11. A solution of a substance ‘X’ is used for white washing. (a) Name the substance ‘X’ and write its formula.(b) Write the reaction of the substance ‘X’ named in (a) above with water.
  12. What is the difference between displacement and double displacement reactions? Write example of each reaction.
  13. Why should magnesium ribbon be cleaned before burning in air?
  14. Explain the oxidation in terms of gain or loss of oxygen with examples.
  15. What do you understand by corrosion?
  16. What is a chemical reaction?
  17. Define rancidity.
  18. What is meant by oxidation?
  19. What are displacement reactions?
  20. What is catalytic decomposition?
  21. What do you understand by a balanced chemical equation? Why should the chemical equation be Balanced?
  22. (a) Sodium + Water Sodium hydroxide + Hydrogen
    (b) Barium Chloride + Aluminium Sulphate Barium Sulphate + Aluminium Chloride
    (c) Hydrogen sulphide + Oxygen Water + Sulphur dioxide

  23. Why respiration is considered an exothermic reaction? Explain.
  24. What is the difference between combination and decomposition reaction? Give one example of each type.
  25. What type of reaction is represented by the digestion of food in our body?
  26. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
  27. What are double displacement reactions? Give an example.


  1. Electricity
  2. Light Reflestion and Refraction Human Eye and The Colourful World
  3. Source of Energy
  4. Our Environment/Management of Natural Resources
  5. Life Processes
  6. Control and Coordination
  7. Reproduction
  8. Heredity and Variation
  9. Chemical Reactions
  10. Acid Bases and Salts
  11. Metals and Non-Metals
  12. Carbon and its Compounds
  13. Periodic Classification of Elements