(a) When a moist blue litmus paper is dipped in a solution of hypochlorous acid, it first turns red and then latter gets decolourised. Explain.
(b) Iodine is liberated when `KI` is added to a solution of `Cu^(2+)` ions but `Cl_(2)` is not liberated when `KCl` is added to a solution of `Cu^(2+)` ions. why?

Explanation

### Step-by-Step Solution

#### Part (a)
1. **Understanding Hypochlorous Acid**: Hypochlorous acid (HClO) is an acid, which means it can donate protons (H⁺ ions) in solution.

2. **Effect on Litmus Paper**: When a moist blue litmus paper is dipped into a solution of hypochlorous acid, the acid donates H⁺ ions, which causes the blue litmus paper to turn red. This is a characteristic reaction of acids with litmus paper.

3. **Decolorization Process**: Hypochlorous acid also acts as an oxidizing agent. It can release nascent oxygen (O) in solution. The nascent oxygen has bleaching properties.
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