Question

In the reaction of $FeS{O}_4$ with $K_{2}C{r}_2{O}_7$ in the presence of an acid, the changes in the formal oxidation numbers of Cr and Fe are _________ respectively.

• A. 1 and 5
• B. 3 and 1
• C. 5 and 1
• D. 1 and 3

Answer 1

Answer: (B)

3 and 1

$C{r}_2{O}_7^{2-}+6F{e}^{2+}+14H^{+}\to 6F{e}^{3+}+2C{r}^{3+}+7H_{2}O$
Change in oxidation number of Cr is $=6-3=3$
Change in oxidation number of Fe is $=3-2=1$