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In the separation of Cu^(2+) and Cd^(2+)...

In the separation of `Cu^(2+)` and `Cd^(2+)` of Iind group in qualitative analysis of cations, tetraamminecopper (II) sulphate and tetramminecadmium (II) sulphate react with KCN to form the corresponding cyano complex. Which one of the following pairs of the complexes and their relative stability enables the separation of `Cu^(2+)` and `Cd^(2+)` ?

A

`K_(3)[Cu(CN)_(4)]`: less stable and `K_(2)[Cd(CN)_(4)]`: more stable

B

`K_(3)[Cu(CN)_(4)]`: more stable and `K_(2)[Cd(CN)_(4)]`: less stable

C

`K_(2)[Cu(CN)_(4)]`: less stable and `K_(2)[Cd(CN)_(4)]`: more stable

D

`K_(2)[Cu(CN)_(4)]`: more stable and `K_(2)[Cd(CN)_(4)]`: less stable

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem of separating `Cu^(2+)` and `Cd^(2+)` in qualitative analysis, we need to analyze the stability of the complexes formed when these cations react with KCN. Here’s a step-by-step breakdown of the solution: ### Step 1: Identify the complexes formed - **Tetraamminecopper(II) sulfate** reacts with KCN to form **Tetraamminecopper(II) cyanide** (K3Cu(CN)4). - **Tetramminecadmium(II) sulfate** reacts with KCN to form **Tetramminecadmium(II) cyanide** (K2Cd(CN)4). ### Step 2: Write the reactions 1. For copper: \[ \text{Cu(NH}_3\text{)}_4\text{SO}_4 + 4 \text{KCN} \rightarrow \text{K}_3\text{Cu(CN)}_4 + \text{K}_2\text{SO}_4 + 4 \text{NH}_4\text{OH} \] 2. For cadmium: \[ \text{Cd(NH}_3\text{)}_4\text{SO}_4 + 4 \text{KCN} \rightarrow \text{K}_2\text{Cd(CN)}_4 + \text{K}_2\text{SO}_4 + 4 \text{NH}_4\text{OH} \] ### Step 3: Analyze the stability of the complexes - The stability of metal complexes is influenced by the size of the central metal ion. - **Cu^(2+)** is smaller than **Cd^(2+)**, which gives it a higher charge density. Higher charge density typically leads to greater stability of the complex. - Therefore, the stability order can be inferred as: \[ \text{Stability: } K_3\text{Cu(CN)}_4 > K_2\text{Cd(CN)}_4 \] ### Step 4: Conclusion - The greater stability of the copper complex compared to the cadmium complex allows for the effective separation of `Cu^(2+)` and `Cd^(2+)`. - The correct answer to the question is option **B**, which indicates that the stability of the complexes formed enables the separation of the two cations.
To solve the problem of separating `Cu^(2+)` and `Cd^(2+)` in qualitative analysis, we need to analyze the stability of the complexes formed when these cations react with KCN. Here’s a step-by-step breakdown of the solution: ### Step 1: Identify the complexes formed - **Tetraamminecopper(II) sulfate** reacts with KCN to form **Tetraamminecopper(II) cyanide** (K3Cu(CN)4). - **Tetramminecadmium(II) sulfate** reacts with KCN to form **Tetramminecadmium(II) cyanide** (K2Cd(CN)4). ### Step 2: Write the reactions 1. For copper: ...
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