Question

The number of ions formed on dissolving one mole of $ \text{K_3[\text{Fe}(\text{CN})_6] $ in water is:}

• A. 3
• B. 4
• C. 5
• D. 6

Hint:

Coordination compounds like $ \text{K}_3[\text{Fe}(\text{CN})_6] $ dissociate into outer-sphere ions (like $ \text{K}^+ $) and retain the inner complex ion intact in solution.

Answer 1

The Correct Option is B

Step 1: Understand the dissociation of the coordination compound
The compound $ \text{K}_3[\text{Fe}(\text{CN})_6] $ is a coordination complex. When dissolved in water, it dissociates into its constituent ions. $$ \text{K}_3[\text{Fe}(\text{CN})_6] \rightarrow 3\text{K}^+ + [\text{Fe}(\text{CN})_6]^{3-} $$ This means:
3 potassium ions ($ \text{K}^+ $) are released.
One complex ion $ [\text{Fe}(\text{CN})_6]^{3-} $ remains intact and does not further dissociate.
Step 2: Total number of ions formed
From one mole of $ \text{K}_3[\text{Fe}(\text{CN})_6] $, we get:
3 $ \text{K}^+ $ ions
1 $ [\text{Fe}(\text{CN})_6]^{3-} $ ion
So, total = $ 3 + 1 = 4 $ ions. Step 3: Conclusion
The total number of ions formed in solution is: $$ (2) 4 $$