Assertion (A): Chlorine can displace iodide ions from KI solution.

Reason (R): It is an example of displacement reaction.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): Silver is displaced by copper from the aqueous solution of silver nitrate.

Reason (R): Copper is placed below silver in the activity series.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Which is the most reactive element in this question :

CuSO₄ + Fe ⟶ FeSO₄ + Cu

Define :

(a) Photochemical reaction

(b) Electrochemical reaction

Give one example in each case.