Chemistry - Thermochemistry Question with Solution | TestHub

Given,

$\frac{1}{2}{\text{H}}_2\left(\text{g}\right)+\left(\text{aq}\right)\to {\text{H}}^{\text{+}}\left(\text{aq}\right)+e^{-};{\text{ΔH}}^{\text{o}}=0\dots .\left(\text{i}\right)$

$\frac{1}{2}{\text{H}}_2\left(\text{g}\right)+\frac{1}{2}{\text{Cl}}_2\left(\text{g}\right)\to \text{HCl}\left(\text{g}\right);{\text{ΔH}}^{\text{o}}=-92.4\text{ kJ}\dots \left(\text{ii}\right)$

$$\text{HCl}\left(\text{g}\right)+{\text{nH}}_2\text{O}\left(\text{l}\right)\to {\text{ H}}^{+}\left(\text{aq}\right)+{\text{Cl}}^{-}\left(\text{aq}\right);{\text{ΔH}}^{\text{o}}=-74.8\text{ kJ}\dots \left(\text{iii}\right)$$$$\text{HCl}\left(\text{g}\right)+{\text{nH}}_2\text{O}\left(\text{l}\right)\to {\text{ H}}^{+}\left(\text{aq}\right)+{\text{Cl}}^{-}\left(\text{aq}\right);{\text{ΔH}}^{\text{o}}=-74.8\text{ kJ}\dots \left(\text{iii}\right)$$

$\left(\text{i}\text{i}\right)+\left(\text{i}\text{i}\text{i}\right)-\left(\text{i}\right)$

$\therefore \frac{1}{2}{\text{Cl}}_2\left(\text{g}\right)+\left(\text{aq}\right)+e^{-}\to {\text{Cl}}^{-}\left(\text{aq}\right);\text{ΔH}=\left(-92.4-74.8\right)\text{ kJ}-167.2\text{ kJ}\dots .\left(\text{iv}\right)$

Heat of formation for${\text{Cl}}^{-}\left(\text{aq}\right)=-167.2\text{ kJ}$