Question

The balanced equation in acidic medium is :

${ClO}_3^{-}+F{e}^{2+}\stackrel{H+}{⟶}C{l}^{-}+F{e}^{3+}+H_{2}O$

• A. $6H^{+}+{ClO}_3^{-}+6F{e}^{2+}\to C{l}^{-}+6F{e}^{3+}+3H_{2}O$
• B. $3H^{+}+{ClO}_3^{-}+9F{e}^{2+}\to C{l}^{-}+6F{e}^{3+}+3H_{2}O$
• C. $6H^{+}+{ClO}_3^{-}+12F{e}^{2+}\to C{l}^{-}+4F{e}^{3+}+3H_{2}O$
• D. none of these

Answer 1

Answer: (A)

$6H^{+}+{ClO}_3^{-}+6F{e}^{2+}\to C{l}^{-}+6F{e}^{3+}+3H_{2}O$

The unbalanced redox equation is as follows:
$Cl{O}_3^{-}+F{e}^{2+}\stackrel{H+}{\to }C{l}^{-}+F{e}^{3+}+H_{2}O$
All atoms other than H and O are balanced.
The oxidation number of Fe changes from +2 to +3. The change in the oxidation number of Fe is 1.
The oxidation number of Cl changes from +5 to -1. The change in the oxidation number of Cl is 6.
The increase in the oxidation number is balanced with decrease in the oxidation number by multiplying $F{e}^{2+}$ and $F{e}^{3+}$ with 6.
$Cl{O}_3^{-}+6F{e}^{2+}\stackrel{H+}{\to }C{l}^{-}+6F{e}^{3+}+H_{2}O$
O atoms are balanced by adding 2 water molecules on RHS.
$Cl{O}_3^{-}+6F{e}^{2+}\stackrel{H+}{\to }C{l}^{-}+6F{e}^{3+}+3H_{2}O$
Hydrogen atoms are balanced by adding 6 $H^{+}$ atoms on the LHS.
$Cl{O}_3^{-}+6F{e}^{2+}\stackrel{H+}{+}6H^{+}\to C{l}^{-}+6F{e}^{3+}+3H_{2}O$
This is the balanced chemical equation.