The figure given below demonstrates the preparation of oxygen.

2KClO₃ (s) $\xrightarrow{\text{MnO}{_2}/{\text {heat}}}$ 2KCl (s) + 3O₂ (g)

(I) Which of the following statements is/are correct about the reaction?

1. It is a decomposition reaction and is exothermic.

2. It is a decomposition reaction and is endothermic.

3. It is a photochemical decomposition reaction.

4. It is a combination reaction.

(II) Potassium chlorate is:

1. an oxidising agent.

2. a reducing agent.

3. both reducing as well as an oxidising agent.

4. all options are correct.

(III) In the reaction, manganese dioxide:

1. takes part in the reaction.

2. acts as a catalyst.

3. decreases the speed of reaction.

4. helps in producing more oxygen.

What happens when a solution of an acid is mixed with a solution of a base in a test tube?

P — The temperature of the solution increases.

Q — The temperature of the solution decreases.

R — The temperature of the solution remains the same.

S — Salt formation takes place.

1. Only P

2. P and R

3. Q and R

4. P and S

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.