Assertion : Cu^{2+} and Cd^{2+} are separated | vedclass

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(A) When $KCN$ is added to a mixture of $Cu^{2+}$ and $Cd^{2+}$,$Cu^{2+}$ is reduced to $Cu^{+}$ by $CN^-$ ions,forming the stable complex $K_3[Cu(CN)

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If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

Vedclass · Answer

(A) When $KCN$ is added to a mixture of $Cu^{2+}$ and $Cd^{2+}$,$Cu^{2+}$ is reduced to $Cu^{+}$ by $CN^-$ ions,forming the stable complex $K_3[Cu(CN)_4]$.$Cd^{2+}$ also forms a complex,$K_2[Cd(CN)_4]$,but it is less stable than the copper complex.When $H_2S$ gas is passed through this solution,the $Cd^{2+}$ complex dissociates to provide enough $Cd^{2+}$ ions to react with $S^{2-}$ and form a yellow precipitate of $CdS$.However,the $Cu^{+}$ complex is highly stable and does not dissociate to provide sufficient $Cu^{+}$ ions to form $Cu_2S$.Thus,$Cu^{2+}$ and $Cd^{2+}$ are separated. Both the assertion and the reason are correct,and the reason explains why $Cu^{2+}$ does not precipitate.

Assertion : $Cu^{2+}$ and $Cd^{2+}$ are separated from each other by first adding $KCN$ solution and then passing $H_2S$ gas.
Reason : $KCN$ reduces $Cu^{2+}$ to $Cu^{+}$ and forms a complex with it.

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Assertion : $Cu^{2+}$ and $Cd^{2+}$ are separated from each other by first adding $KCN$ solution and then passing $H_2S$ gas.Reason : $KCN$ reduces $Cu^{2+}$ to $Cu^{+}$ and forms a complex with it.