Question

The oxidation number of Cu in the ion [Cu(CN)$_4$]$^{3-}$ is

• A. +2
• B. +3
• C. +1
• D. –7

Hint:

Always balance total oxidation states with overall charge of the complex ion.

Answer 1

The Correct Option is C

Step 1: Apply oxidation number rule.
Let oxidation number of Cu = $x$.
Charge on cyanide (CN$^-$) = –1 each.
There are 4 CN$^-$ ligands $\Rightarrow$ total = –4.
Step 2: Write equation.
$x + (-4) = -3$
$x - 4 = -3$
$x = +1$
Step 3: Conclude.
Oxidation number of Cu is +1. Final Answer: \[ \boxed{+1} \] % Quciktip