Question

Which of the following acts as a reducing agent?

• A. $HN{O}_3$
• B. $KMn{O}_4$
• C. $H_{2}S{O}_4$
• D. $(COOH{)}_2$

Answer 1

Answer: (D)

The O.N, of $C$ increases from $+3$ in $(COOH{)}_2$ to $+4$ in $C{O}_2$, therefore, it acts as a reducing agent
$(C^{+3}OOH{)}_2\to 2C^{+4}{O}_2$
In all the remaining compounds, one element has already the maximum possible O.N., i.e., $N$ has $+5$ in $HN{O}_3$, $Mn$ has $+7$ in $KMn{O}_4$ and $S$ has $+6$ in $H_{2}S{O}_4$ and they cannot further increase their G.N. and hence cannot act as reducing agents.