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.

State the changes observed in the following chemical reactions.

(a) A small piece of sodium is dropped in water.

(b) Few iron filings are added to blue copper sulphate solution.

(c) Water is added to quick lime (CaO).

(d) Hydrochloric acid is added to metal sulphide.