Out of $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ and $\mathrm{CuCl}_{2}$, which is more stable and why ?
$\mathrm{CuCl}_{2}$ is more stable because of higher stability of $\mathrm{Cu}^{2+}$ ion due to high negative value of hydration enthalpy of $\mathrm{Cu}^{2+}$ than $\mathrm{Cu}^{+}$.