Heat of neutralization of strong acid against strong base is constant and is equal to

Options

A. 13.7 kcal
B. 57 kJ
C. `5.7 xx 10^(4) J`
D. All of the above

Answer

### Step-by-Step Solution:

1. **Understanding Neutralization**:
- Neutralization is a chemical reaction between an acid and a base that produces a salt and water. In this case, we are considering a strong acid (HCl) and a strong base (NaOH).

2. **Identifying the Reaction**:
- The reaction can be written as:
\[ \text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O} \]
- When HCl dissociates, it produces H⁺ and Cl⁻ ions, and when NaOH dissociates, it produces Na⁺ and OH⁻ ions.

3. **Net Ionic Equation**:
- The net ionic equation for the neutralization reaction is:
\[ \text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O} \]
- This shows that the heat of neutralization is essentially the heat released when H⁺ ions react with OH⁻ ions to form water.

4. **Heat of Neutralization**:
- The heat of neutralization for strong acids and strong bases is constant and is equal to the heat of formation of water from its ions.

5. **Value of Heat of Neutralization**:
- The value of the heat of neutralization is approximately:
\[ 57 \text{ kJ/mol} \]
- This can also be expressed as:
\[ 5.7 \times 10^4 \text{ J/mol} \]
- Additionally, converting this value to kilocalories gives:
\[ 57 \text{ kJ} \approx 13.7 \text{ kcal} \]

6. **Conclusion**:
- Therefore, the heat of neutralization of a strong acid against a strong base is constant and equal to 57 kJ, which can also be expressed in other units as mentioned above.

### Final Answer:
The heat of neutralization of a strong acid against a strong base is constant and is equal to **57 kJ** (or **5.7 x 10^4 J** or **13.7 kcal**).

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