Q10 / 180 · KCET 2020 · Chemistry

For $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ and $\mathrm{CuCl}_{2}$ in aqueous medium, which of the following statement is correct?

  • Correct answer
    A
    $\mathrm{CuCl}_{2}$ is more stable than $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$
  • B
    Stability of $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ is equal to stability of $\mathrm{CuCl}_{2}$
  • C
    Both are unstable
  • D
    $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ is more stable than $\mathrm{CuCl}_{2}$

Solution

Out of $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ and $\mathrm{CuCl}_{2}$ in aqueous medium, $\mathrm{CuCl}_{2}$ is more stable than $\mathrm{Cu}_{2} \mathrm{Cl}_{2}$ as $\mathrm{Cu}^{2+}(a q)$ is more stable than $\mathrm{Cu}^{+}(a q)$ due to more negative enthalpy of hydration which compensates for the second ionisation enthalpy of $\mathrm{Cu}$. In $\mathrm{CuCl}_{2}, \mathrm{Cu}$ is in $\mathrm{Cu}^{2+}$ state and in $\mathrm{Cu}_{2} \mathrm{Cl}_{2}, \mathrm{Cu}$ is in $\mathrm{Cu}^{+}$state

Hence, the correct answer is option: 'A'.

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