(i) Answer the following questions:
a) Arrange the following in the increasing order of thermal stability:
`H_(2)O, H_(2)S, H_(2)Se, H_(2)Te`
b)Give the formula of the brown ring formed at the interface during the ring test for nitrate.
(ii) A greenish yellow gas ‘A’ with pungent and suffocating odour, is a powerful bleaching agent. ‘A’ on treatment with dry slaked lime it gives bleaching powder. Identify ‘A’ and explain the reason for its bleaching action. Write the balanced chemical equation for the reaction of ‘A’ with hot and concentrated NaOH.

Explanation

### Step-by-Step Solution

#### (i) a) Arrange the following in the increasing order of thermal stability: `H₂O, H₂S, H₂Se, H₂Te`

1. **Identify the Compounds**: The compounds are water (H₂O), hydrogen sulfide (H₂S), hydrogen selenide (H₂Se), and hydrogen telluride (H₂Te).

2. **Understand Thermal Stability**: Thermal stability refers to the ability of a compound to resist decomposition when heated. A more thermally stable compound will decompose at a higher temperature.

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