The enthalpy of neutralisation of a weak acid in `1 M` solution with a strong base is `-5.6 kJ mol^(-1)`. Enthalpy of ionization of the acid is `1.5 kJ mol^(-1)` and enthalpy of neutralization of the strong acid with a strong base is `-57.3 kJ"equiv"^(-1)`, what is the % ionization of the weak acid in molar solution (assume the acid to be monobasic) ?

Answer

To solve the problem step by step, we need to calculate the percentage ionization of the weak acid based on the provided enthalpy values.

### Step 1: Understand the given data
- Enthalpy of neutralization of the weak acid with a strong base (ΔH_neutralization, weak acid) = -5.6 kJ/mol
- Enthalpy of ionization of the weak acid (ΔH_ionization) = 1.5 kJ/mol
- Enthalpy of neutralization of a strong acid with a strong base (ΔH_neutralization, strong acid) = -57.3 kJ/mol

### Step 2: Calculate the enthalpy change due to ionization of the weak acid
The enthalpy of ionization can be expressed as:
\[ \Delta H_{\text{ionization}} = \Delta H_{\text{neutralization, weak acid}} - \Delta H_{\text{neutralization, strong acid}} \]

Substituting the values:
\[ \Delta H_{\text{ionization}} = (-5.6 \text{ kJ/mol}) - (-57.3 \text{ kJ/mol}) \]
\[ \Delta H_{\text{ionization}} = -5.6 + 57.3 = 51.7 \text{ kJ/mol} \]

### Step 3: Calculate the effective enthalpy of ionization of the weak acid
Now, we know the enthalpy of ionization of the weak acid is given as 1.5 kJ/mol. We can find the effective enthalpy of ionization:
\[ \Delta H_{\text{effective}} = \Delta H_{\text{ionization}} - \Delta H_{\text{ionization, weak acid}} \]
\[ \Delta H_{\text{effective}} = 51.7 \text{ kJ/mol} - 1.5 \text{ kJ/mol} = 50.2 \text{ kJ/mol} \]

### Step 4: Calculate the percentage ionization
The percentage ionization can be calculated by the formula:
\[ \text{Percentage Ionization} = \left( \frac{\Delta H_{\text{effective}}}{\Delta H_{\text{ionization}}} \right) \times 100 \]
Substituting the values:
\[ \text{Percentage Ionization} = \left( \frac{50.2 \text{ kJ/mol}}{51.7 \text{ kJ/mol}} \right) \times 100 \]
\[ \text{Percentage Ionization} \approx 97.1\% \]

### Conclusion
The percentage ionization of the weak acid in a 1 M solution is approximately **97.1%**.