The enthalpy of neutralization is about 57.3 kJ for the pair

Options

A. `HCl and NH_(4)OH`
B. `NH_(4)OH and HNO_(3)`
C. HCl and NaOH
D. `CH_(3)COOH and NaOH`

Explanation

To solve the question regarding the enthalpy of neutralization, we need to understand the concept of enthalpy changes during neutralization reactions. Here is a step-by-step solution:

### Step-by-Step Solution:

1. **Understanding Enthalpy of Neutralization**:
The enthalpy of neutralization is the heat change that occurs when an acid and a base react to form water and a salt. For strong acids and strong bases, this value is typically around -57.3 kJ/mol.

2. **Identifying Strong and Weak Acids/Bases**:
- Strong acids (like HCl) completely dissociate in water.
- Strong bases (like NaOH) also completely dissociate in water.
- Weak acids (like CH3COOH) and weak bases (like NH4OH) do not completely dissociate.

3. **Analyzing the Given Pairs**:
- If both the acid and base are strong, the enthalpy of neutralization will be approximately -57.3 kJ.
- If one of the reactants is a weak acid or a weak base, some of the heat released during the reaction is used for the ionization of the weak component, resulting in a lower enthalpy of neutralization.

4. **Applying to the Given Example**:
- In the case of HCl (strong acid) and NH4OH (weak base), the enthalpy of neutralization will be less than -57.3 kJ because NH4OH does not completely ionize.
- Similarly, if we consider other pairs like CH3OH (weak acid) and NH4OH (weak base), the enthalpy will also be less than -57.3 kJ.

5. **Conclusion**:
- For strong acid and strong base pairs, the enthalpy of neutralization is around -57.3 kJ.
- For weak acid or weak base combinations, the enthalpy will be lower than -57.3 kJ.

### Final Answer:
The enthalpy of neutralization for combinations where at least one component is weak will be less than -57.3 kJ.