Question

How many electrons are involved in the following redox reaction?
$C{r}_2{O}_7^{2-}+F{e}^{2+}+C_2{O}_4^{2-}\to C{r}^{3+}+F{e}^{3+}+C{O}_2$ (Unbalanced)

• A. 3
• B. 4
• C. 6
• D. 5

Answer 1

Answer: (C)

$C{r}_2{O}_7^{2-}+2F{e}^{2+}+2C_2{O}_4^{2-}\to 2C{r}^{3+}+2F{e}^{3+}+4C{O}_2$
The oxidation number of chromium in $C{r}_2{O}_7^2$ is $+6$ and it reduces to $+3$ in $C{r}^{3+}$.
On balancing the equation, we will see 2 moles of chromium ion goes from $+6$ to $+3$.
Hence, there are 6 electrons involved in the above redox reaction.