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

To solve the question regarding the heat of neutralization of a strong acid against a strong base, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The neutralization reaction between a strong acid (like HCl) and a strong base (like NaOH) can be represented as:
\[ \text{H}^+_{\text{(aq)}} + \text{OH}^-_{\text{(aq)}} \rightarrow \text{H}_2\text{O}_{\text{(l)}} \]
- This reaction produces water (H₂O) and releases heat.

2. **Definition of Heat of Neutralization**:
- The heat of neutralization is defined as the amount of heat released when one equivalent of acid reacts with one equivalent of base to form water.
- For strong acids and strong bases, this value is constant.

3. **Heat Released in the Reaction**:
- When one mole of HCl reacts with one mole of NaOH, it completely ionizes:
- HCl → H⁺ + Cl⁻
- NaOH → Na⁺ + OH⁻
- Therefore, the overall reaction simplifies to:
\[ \text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O} \]
- The heat released during this neutralization is approximately -57 kJ (negative sign indicates that heat is released).

4. **Conversion to Other Units**:
- To convert kilojoules to kilocalories, we use the conversion factor:
\[ 1 \text{ kJ} = 0.239 \text{ kcal} \]
- Thus, converting 57 kJ to kilocalories:
\[ 57 \text{ kJ} \times 0.239 \text{ kcal/kJ} \approx 13.7 \text{ kcal} \]

5. **Conclusion**:
- The heat of neutralization for the reaction of a strong acid with a strong base is constant and is equal to approximately -57 kJ or 13.7 kcal.
- Therefore, the correct answer to the question is that the heat of neutralization is equal to -57 kJ or 13.7 kcal.

### Final Answer:
The heat of neutralization of a strong acid against a strong base is constant and is equal to -57 kJ (or 13.7 kcal).

---