In quantitative analysis of second group in laboratory, `H_2S` gas is passed in acidic medium for precipitation. When `Cu^(2+)` and `Cd^(2+)` react with `KCN`, then for product true statement is

Options

A. (a) `K_2[Cu(CN)_4]` more soluble
B. (b) `K_2[Cd(CN)_4]` less stable
C. (c) `K_2[Cd(CN)_3]` more stable
D. (d) `K_3[Cu(CN)_2]` less stable

Explanation

To solve the question regarding the reaction of \(Cu^{2+}\) and \(Cd^{2+}\) with \(KCN\) and to find the true statement about the products, we will follow these steps:

### Step 1: Understand the Reaction
When \(Cu^{2+}\) and \(Cd^{2+}\) react with \(KCN\), they form coordination complexes. The cyanide ion (\(CN^-\)) acts as a ligand and coordinates with the metal ions.

### Step 2: Determine the Oxidation States
For both \(Cu^{2+}\) and \(Cd^{2+}\), the oxidation state is +2. This is important because the stability of coordination compounds often depends on the oxidation state of the central metal ion.

### Step 3: Analyze Stability of Complexes
In coordination chemistry, the stability of a complex is generally higher when the oxidation state of the metal is higher. Since both \(Cu^{2+}\) and \(Cd^{2+}\) are in the +2 oxidation state, we need to compare the stability of their respective complexes formed with \(CN^-\).

### Step 4: Compare Solubility and Stability
- The stability of a coordination compound is inversely related to its solubility. A more stable complex will typically be less soluble in solution.
- Since both \(Cu^{2+}\) and \(Cd^{2+}\) form stable complexes with \(CN^-\), we need to identify which one is more stable.

### Step 5: Conclusion on Stability
- \(Cu(CN)_4^{2-}\) is known to be more stable than \(Cd(CN)_4^{2-}\) due to the higher ligand field stabilization energy associated with \(Cu^{2+}\).
- Therefore, the correct statement regarding the products is that the complex formed with \(Cu^{2+}\) is more stable than that formed with \(Cd^{2+}\).

### Final Answer
The true statement regarding the products of the reaction of \(Cu^{2+}\) and \(Cd^{2+}\) with \(KCN\) is that the complex with \(Cu^{2+}\) is more stable than the complex with \(Cd^{2+}\).

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