The pair of exothermic hydrides of VI A group are 

Options

A. `H_(2)O, H_(2)S`
B. `H_(2)O, H_(2)Se`
C. `H_(2)Se, H_(2)Te`
D. `H_(2)S, H_(2)Te`

Answer

To determine the pair of exothermic hydrides of the VI A group, we will analyze the hydrides formed by the elements in this group and their enthalpy changes during formation.

### Step-by-Step Solution:

1. **Identify the Group**: The VI A group (or Group 16) of the periodic table includes the elements Oxygen (O), Sulfur (S), Selenium (Se), Tellurium (Te), and Polonium (Po).

2. **List the Hydrides**: The hydrides formed by these elements are:
- H2O (Water)
- H2S (Hydrogen Sulfide)
- H2Se (Hydrogen Selenide)
- H2Te (Hydrogen Telluride)

3. **Understand Exothermic Reactions**: An exothermic reaction is one that releases heat. In the context of hydrides, this means that when the hydride is formed from its elements, the enthalpy change (ΔH) is negative.

4. **Analyze the Formation of Each Hydride**:
- For H2O:
\[ \text{H}_2 + \text{O}_2 \rightarrow \text{H}_2\text{O} \quad (\Delta H = -286 \text{ kJ/mol}) \]
- For H2S:
\[ \text{H}_2 + \text{S} \rightarrow \text{H}_2\text{S} \quad (\Delta H = -20 \text{ kJ/mol}) \]
- For H2Se:
\[ \text{H}_2 + \text{Se} \rightarrow \text{H}_2\text{Se} \quad (\Delta H = +85.7 \text{ kJ/mol}) \]
- For H2Te:
\[ \text{H}_2 + \text{Te} \rightarrow \text{H}_2\text{Te} \quad (\Delta H = +0.27 \text{ kJ/mol}) \]

5. **Determine Exothermic Hydrides**: From the above reactions, we see that:
- H2O and H2S have negative ΔH values, indicating they are exothermic.
- H2Se and H2Te have positive ΔH values, indicating they are endothermic.

6. **Conclusion**: The pair of exothermic hydrides of the VI A group is H2O and H2S.

### Final Answer:
The pair of exothermic hydrides of the VI A group are **H2O and H2S**.

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