NEET (UG) 2023 — Question 48

The stability of $\mathrm{Cu}^{2+}(\mathrm{aq})$ is more than $\mathrm{Cu}^{+}(\mathrm{aq})$

is due to the much more negative $\Delta$ hyd $\mathrm{H}^{\circ}$ of

$\mathrm{Cu}^{2+}(\mathrm{aq})$ than $\mathrm{Cu}^{+}(\mathrm{aq})$,

which more than compensates for second ionisation enthalpy of Cu .

$$\begin{aligned} & \Delta_{\text {hyd }} \mathrm{H}^{\circ} \text { of } \mathrm{Cu}^{2+}(\mathrm{aq})=-2121 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta_{\mathrm{i}} \mathrm{H}_1^{\circ} \text { of } \mathrm{Cu}=+745 \mathrm{~kJ} \mathrm{~mol}^{-1} \\ & \Delta_{\mathrm{i}} \mathrm{H}_2^{\circ} \text { of } \mathrm{Cu}=+1960 \mathrm{~kJ} \mathrm{~mol}^{-1} \end{aligned}$$