Cu$^{+}$in aqueous solution undergoes disproportionation, i.e.,2Cu$^{+}$$_{\mathrm{aq}}$ → Cu$^{2+}$$_{\mathrm{aq}}$+ Cu(s)The stability of Cu$^{2+}$$_{\mathrm{aq}}$ rather than Cu$^{ +}$$_{\mathrm{aq}}$ is due to the much more negative$\Delta_{\mathrm{hyd}}$H° of Cu$^{2+}$$_{\mathrm{aq}}$ than Cu$^{+}$, which more than compensates for the secondionisation enthalpy of Cu.