Which of the following acids will not evolve `H_(2)` gas on reaction with alkali metals?

Options

A. hydrazoic acid
B. perxenic acid
C. boric acid
D. none of these

Explanation

To determine which of the following acids will not evolve hydrogen gas when reacting with alkali metals, we need to analyze the behavior of each acid in the presence of alkali metals such as lithium, sodium, potassium, rubidium, and cesium.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
Alkali metals typically react with acids to produce hydrogen gas. The general reaction can be represented as:
\[ \text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{H}_2 \text{(gas)} \]
However, some acids do not produce hydrogen gas when they react with alkali metals.

2. **Analyzing Hydrazine Acid (N3H)**:
- When sodium reacts with hydrazoic acid (N3H), it produces sodium azide (NaN3) and nitrogen gas (N2) instead of hydrogen gas.
- Therefore, hydrazoic acid does not evolve hydrogen gas on reaction with alkali metals.

3. **Analyzing Perzanic Acid (Re2O7)**:
- Perzanic acid does not release hydrogen gas when it reacts with alkali metals. Instead, it forms perrhenate salts without evolving hydrogen.
- Thus, perzanic acid also does not evolve hydrogen gas.

4. **Analyzing Boric Acid (H3BO3)**:
- Boric acid does not release hydrogen gas when it reacts with alkali metals. Instead, it forms borate salts.
- Therefore, boric acid does not evolve hydrogen gas upon reaction with alkali metals.

5. **Conclusion**:
All three acids mentioned (hydrazoic acid, perzanic acid, and boric acid) do not evolve hydrogen gas when they react with alkali metals.

### Final Answer:
The acids that will not evolve H2 gas on reaction with alkali metals are:
- Hydrazine Acid (N3H)
- Perzanic Acid (Re2O7)
- Boric Acid (H3BO3)