Question

How many electrons are involved in the following redox reaction?
$Cr_2O^{2-}_{7}+Fe^{2+}+C_2O^{2-}_{4} \to Cr^{3+}+Fe^{3+}+CO_2$ (Unbalanced)

• A. 3
• B. 4
• C. 6
• D. 5

Answer 1

Answer: (C)

$Cr _{2} O_{7}^{2-}+2 F e ^{2+}+2 C _{2} O _{4}^{2-} \rightarrow 2 Cr ^{3+}+2 F e ^{3+}+4 CO _{2}$
The oxidation number of chromium in $Cr _{2} O _{7}^{2}$ is $+6$ and it reduces to $+3$ in $Cr ^{3+}$.
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.