Question

The permanganate ion is an excellent oxidizing agent in aqueous solutions. When the half reaction, $Mn{O}_4{}^{-}+H^{+}+e^{-}\to Mn{O}_2+H_{2}O$ is balanced, the correct coefficients for the species involved are:

• A. 1, 4, 4, 1, 2
• B. 1, 4, 2, 1, 2
• C. 1, 4, 3, 1, 2
• D. 1, 4, 1, 1, 2

Answer 1

Answer: (C)

1, 4, 3, 1, 2

The unbalanced half reaction is $Mn{O}_4^{-}+H^{+}+e^{-}\to Mn{O}_2+H_{2}O$
$Mn$ atoms ar aleady balanced.

Balance $O$ atoms by adding a water molecule on the right-hand side.

$Mn{O}_4^{-}+H^{+}+e^{-}\to Mn{O}_2+2H_{2}O$

Balance H atoms by adding 3 protons on left-hand side:

$Mn{O}_4^{-}+4H^{+}+e^{-}\to Mn{O}_2+2H_{2}O$

Balance charges by adding 2 electrons on left hand side:

$Mn{O}_4^{-}+4H^{+}+3e^{-}\to Mn{O}_2+2H_{2}O$

This is a balanced half-reaction.

The correct coefficients for the species involved are $1,4,3,1,2$

Hence, the option $C$ is the correct answer.