Question

Determine the oxidation state of the underlined element in $K\underset{–}{Au}{Cl}_4$.

• A. $+3$
• B. $+2$
• C. $+4$
• D. none of these

Answer 1

The correct option is A $+3$

Let $x$ be the oxidation number of $Au$ in $KAuC{l}_4$.
The oxidation numbers of $K$ and $Cl$ are $+1$ and $-1$ respectively.
Since the overall charge on the complex is $0$, the sum of oxidation states of all elements in it should be equal to $0$.
Therefore, $+1+x+4(-1)=0$
$x-3=0$
$x=+3$
Hence, the oxidation number of $Au$ in $KAuC{l}_4$ is $+3$.