Page 67 - Chemistry ICSE Class IX

Chemical Changes and Reactions 55
14. (a) How does light affect chemical reactions?

(b) Give two processes/reactions which are affected by light.
15. Describe the double displacement reaction giving suitable example.
16. Is the following reaction exothermic or endothermic? Give reason.
C H OH(l) + 3O (g) o 2CO (g) + 3H O(l) + 1368 kJ
2
5
2
2
2
17. Give one example of a redox reaction, naming the substances oxidised and reduced.
18. Explain by giving one example, why do oxidation and reduction proceed side by side.
19. Given below are two reactions. Which is the combination reaction and which is the displacement reaction?
Justify by giving reason.
(a) 2KBr(aq) + Cl (aq) o 2KCl(aq) + Br (aq)
2
2
'
(b) Fe(s) + S(s) o FeS(s)
20. In the reaction represented by the equation,
CuSO (aq) + Zn(s) o Cu(s) + ZnSO (aq)
4
4
(a) ____________ is the oxidising agent, while ____________ is the reducing agent.
(b) ____________ is oxidised while ____________ is reduced.
21. Give two examples of combustion reactions.
22. What are the disadvantages of partial combustion?
23. Why does the burning of a metal in air cause a gain in its mass?
24. Give reasons for the following:
Blue colour of copper sulphate solution is destroyed when iron lings are added to it.

25. Identify the compounds oxidised and reduced in the following reactions:
(a) H S + Cl o 2HCl + S
2
2
(b) 2Na + Cl o 2NaCl
2
26. From among the reactants of the following chemical equations, name the oxidising and reducing agents:
(a) 2Na + Cl o 2NaCl
2
(b) HgCl 2 + Hg o Hg Cl 2
2
(c) CuO + H o Cu + H O
2
2
27. In the following redox reaction:
2+
Cu 2+ + Zn o Cu + Zn
Name the (a) oxidising agent, (b) substance oxidised, (c) substance gaining electrons, and (d) element whose
oxidation number increases.
28. Give possible explanation for the following observations:

(a) When ammonium nitrate is dissolved in water taken in a beaker, the beaker becomes cold.
(b) When magnesium is dissolved in dilute hydrochloric acid, the reaction mixture gets warm.
29. What are the necessary conditions for the process of combustion to take place?
30. Compare the processes of respiration and combustion.
31. What do you mean by exothermic and endothermic reactions? Give examples.
32. Explain the following in terms of gain or loss of oxygen with two examples each:
(a) Oxidation (b) Reduction

33. Account for the oxygen - carbon dioxide balance in nature.
34. Name the consumers and producers of (a) oxygen, (b) carbon dioxide, on the Earth.