Question

Which of the following can act only as a reducing agent?

• A. $K_{2}C{r}_2{O}_7$
• B. $CaOC{l}_2$
• C. $Pb{O}_2$
• D. $H_{2}S$

Answer 1

The correct option is D $H_{2}S$

$S$ can have oxidation states in the range $-2$ to $+6$.

In $H_{2}S$, it has oxidation state of $-2$. Thus, it can only lose electrons.

Hence, $H_{2}S$ can act only as reducing agent.

$K_{2}C{r}_2{O}_7$, $CaOC{l}_2$ and $Pb{O}_2$ are oxidizing agents while $H_{2}S$ is a reducing agent.

Hence, the correct option is $D$