Question

The oxidation number of Fe in \( K_2[Fe(CN)_6] \) is:

• A. +6
• B. +4
• C. +3
• D. -4

Hint:

To find the oxidation state of an element in a complex, balance the charges from the ions and the metal.

Answer 1

The Correct Option is B

Step 1: Understanding the complex.
In the complex \( K_2[Fe(CN)_6] \), the cyanide ion (CN) has a charge of \( -1 \). Since there are 6 cyanide ions, the total charge contributed by cyanides is \( -6 \).

Step 2: Determine the oxidation state of Fe.
Let the oxidation state of Fe be \( x \). The total charge on the complex is \( 0 \), and the charges from the cyanides and potassium ions are: \[ 2(+1) + x + 6(-1) = 0 \Rightarrow 2 + x - 6 = 0 \Rightarrow x = +4. \]

Step 3: Conclusion.
The oxidation state of Fe is \( +4 \), which corresponds to option (2).