The enthalpy of reaction is maximum in which of the following reaction?

Options

A. `NaOH + HCI rightarrow NaCI + H_(2)O`
B. `NaOH + HF rightarrow NaF + H_(2)O`
C. `NaOH + HBr rightarrow NaBr + H_(2)O`
D. All have same value

Answer

To determine which reaction has the maximum enthalpy change, we need to analyze the reactions involving the acids HBr, HCl, and HF when they react with NaOH to form water. The enthalpy change (ΔH) indicates the amount of energy released or absorbed during a reaction.

### Step-by-Step Solution:

1. **Identify the Reactions**:
- The reactions we are considering are:
- HBr + NaOH → NaBr + H2O
- HCl + NaOH → NaCl + H2O
- HF + NaOH → NaF + H2O

2. **Understand the Enthalpy Changes**:
- For the reaction of HBr with NaOH, the enthalpy change (ΔH) is approximately -57.1 kJ. This indicates that this reaction releases a significant amount of energy.
- For HCl with NaOH, the enthalpy change will be slightly less than -57.1 kJ because some energy is required to dissociate HCl.
- For HF with NaOH, since HF is a weak acid, it does not dissociate completely in solution. Therefore, the energy released in this reaction will be less than that of HCl and HBr, as some energy is needed to dissociate HF.

3. **Compare the Enthalpy Changes**:
- HBr (strong acid) releases the most energy: ΔH = -57.1 kJ
- HCl (strong acid) releases slightly less energy than HBr due to dissociation: ΔH < -57.1 kJ
- HF (weak acid) releases the least energy due to incomplete dissociation: ΔH < ΔH for HCl

4. **Conclusion**:
- Since HBr is the strongest acid among the three, it will have the maximum enthalpy change when reacting with NaOH. Thus, the reaction with HBr has the maximum enthalpy change.

### Final Answer:
The enthalpy of reaction is maximum in the reaction involving HBr with NaOH.

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