KCET · Chemistry · d and f Block Elements

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

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 \(\mathrm{CuCl}_{2}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(\mathrm{CuCl}_{2}\) is more stable than \(\mathrm{Cu}_{2} \mathrm{Cl}_{2}\)

Step-by-step Solution

Detailed explanation

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

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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