CBSE Important Questions

Chemical reactions and equations

1. Why should a magnesium ribbon be cleaned before burning in air?
2. What is balanced chemical equation?
3. Why should chemical equation be balanced?
4. Give an example of double displacement reaction?
5. Why does colour of copper sulphate solution change when an iron nail is dipped in it?
6. What is exothermic and endothermic reaction?
7. Why respiration is considered an exothermic reaction?
8. What are the latest techniques used to prevent rancidity?
9. On what basis is a chemical equation is balanced?
10. Why all decomposition reactions are endothermic reaction?
11. When blue salt of copper sulphate is heated it becomes colourless? Why?
12. What does a word equation show?
13. What is meant by thermal decomposition reaction?
14. Explain law of conservation of mass?
15. Enlist importance of a chemical equation?
16. Define combination reaction?
17. What is oxidation?
18. What are oxidizing agents?
19. What are reducing agents?
20. Explain electronic concept of oxidation and reduction?
21. What is corrosion? Give 2 examples.
22. What is rusting?
23. Enlist conditions necessary for rusting?
24. State various methods used to prevent rusting?
25. Describe rancidity?
26. Oil and fat containing food items are flushed with nitrogen. Why?