In the separation of $\mathrm{Cu}^{2+}$ and $\mathrm{Cd}^{2+}$ in 2 nd group qualitative analysis of cations…

In the separation of $\mathrm{Cu}^{2+}$ and $\mathrm{Cd}^{2+}$ in 2 nd group qualitative analysis of cations, tetrammine copper (II) sulphate and tetrammine cadmium (II) sulphate react with $\mathrm{KCN}$ to form the corresponding cyano complexes. Which one of the following pairs of the complexes and their relative stability enable the separation of $\mathrm{Cu}^{2+}$ and $\mathrm{Cd}^{2+?}$
  1. $\mathrm{K}_{3}\left[\mathrm{Cu}(\mathrm{CN})_{4}ight]$ more stable and $\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}ight]$
    less stable
  2. $\mathrm{K}_{2}\left[\mathrm{Cu}(\mathrm{CN})_{4}ight]$ less stable and $\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}ight]$
    more stable
  3. $\mathrm{K}_{2}\left[\mathrm{Cu}(\mathrm{CN})_{4}ight]$ more stable and $\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}ight]$
    less stable
  4. $\mathrm{K}_{3}\left[\mathrm{Cu}(\mathrm{CN})_{4}ight]$ less stable and $\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}ight]$
    more stable

Solution

$\mathrm{K}_{3}\left[\mathrm{Cu}(\mathrm{CN})_{4}ight]$ is more stable whereas $\mathrm{K}_{2}\left[\mathrm{Cd}(\mathrm{CN})_{4}ight]$ is less stable.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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