Define :

(a) Photochemical reaction

(b) Electrochemical reaction.

Give one example in each case.

Give an example of each of the following chemical changes.

(a) A photochemical reaction involving 1. silver salt 2. water

(b) A reaction involving 1. blue solution 2. formation of a dirty green precipitate

(c) Two gases combine to form a white solid.

(d) Two solids combine to form a liquid.

(e) A reaction where color change is noticed.

Give a reason for the following :

(a) Silver nitrate solution is kept in coloured bottles.

(b) Molybdenum is used in the manufacture of ammonia.

(c) A blue solution of copper sulphate changes to green when a piece of iron is added to this solution.

(d) Colourless concentrated sulphuric acid in a test tube changes to blue on adding a small piece of copper to it.

Which of the following is not a characteristic of a chemical change?

(i) It is irreversible

(ii) No net energy change is involved

(iii) New substance is formed

(iv) Involves absorption or liberation of energy