When a strong acid, strong base or their salt are dissolved in water, they are completely ionised. If a strong acid is added to a strong base, `H^(+)` ions from the former combine with `OH^(-)` ions of the latter forming water. The formation of each water molecule liberates a certain quantity of energy and the reaction is exothermic. The heat liberated when one mole of water is formed by combining hydrochloric acid sodium hydroxide is 13.7 kcal. The heat liberated when one mole of water is formed by combining sulphuic acid and sodium hydroxide is

Options

A. 25.5 kcal
B. 8.5 kcal
C. 13.7 kcal
D. 34 kcal

Answer

To solve the problem, we need to determine the heat liberated when one mole of water is formed by combining sulfuric acid (H₂SO₄) and sodium hydroxide (NaOH).

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When sulfuric acid (H₂SO₄) reacts with sodium hydroxide (NaOH), the reaction can be represented as:
\[ H_2SO_4 + 2NaOH \rightarrow Na_2SO_4 + 2H_2O \]
- This shows that one mole of sulfuric acid reacts with two moles of sodium hydroxide to produce one mole of sodium sulfate and two moles of water.

2. **Heat Released per Mole of Water**:
- From the problem statement, we know that the heat liberated when one mole of water is formed by combining hydrochloric acid (HCl) and sodium hydroxide (NaOH) is 13.7 kcal.
- This value represents the energy released during the neutralization reaction where H⁺ ions from the acid combine with OH⁻ ions from the base to form water.

3. **Applying the Same Principle**:
- The same principle applies to the reaction between sulfuric acid and sodium hydroxide. When one mole of water is formed from the reaction of H₂SO₄ and NaOH, the heat released will also be the same.
- Thus, the heat liberated when one mole of water is formed in this reaction is also 13.7 kcal.

4. **Conclusion**:
- Therefore, the heat liberated when one mole of water is formed by combining sulfuric acid and sodium hydroxide is:
\[ \text{Heat liberated} = 13.7 \text{ kcal} \]

### Final Answer:
The heat liberated when one mole of water is formed by combining sulfuric acid and sodium hydroxide is **13.7 kcal**.