Question

An octahedral complex with the formula \(\text{CoCl}_3n\text{NH}_3\) upon reaction with excess of \(\text{AgNO}_3\) solution gives 2 moles of \(\text{AgCl}\). Consider the oxidation state of Co in the complex is \(x\). The value of "x + n" is ______.

• A. 3
• B. 6
• C. 8
• D. 5

Answer 1

The Correct Option is C

The reaction of $[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{Cl}_2$ with excess AgNO$_3$ is as follows:
\[[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{Cl}_2 + \text{excess AgNO}_3 \rightarrow 2\text{AgCl (2 moles)}\]
In the complex $[\text{Co}(\text{NH}_3)_5\text{Cl}]\text{Cl}_2$:
The inner coordination sphere contains 1 Cl ligand.
The outer coordination sphere contains 2 Cl$^-$ ions, which react with AgNO$_3$ to give 2 moles of AgCl.
Let $x$ be the oxidation state of Co. The total charge on the complex is neutral. Therefore:
\[x + 0 \text{ (from 5 NH}_3\text{)} + (-1 \text{ from 1 Cl}) + (-2 \text{ from 2 Cl}^-) = 0\]
\[x - 1 - 2 = 0\]
\[x = +3\]
Here, $n = 5$ (the number of NH$_3$ ligands). Thus:
\[x + n = 3 + 5 = 8\]
Final Answer: $x + n = 8$