Question

Balance the following redox reactions in acidic solutions:

${VO}_4^{3-}+{Fe}^{2+}⟶{Fe}^{3+}+{VO}^{2+}$

• A. ${VO}_4^{3-}+{Fe}^{2+}+6H^{+}⟶{Fe}^{3+}+{VO}^{2+}+3H_{2}O$
• B. ${VO}_4^{3-}+3{Fe}^{2+}+6H^{+}⟶{4Fe}^{3+}+{VO}^{2+}+3H_{2}O$
• C. $2{VO}_4^{3-}+3{Fe}^{2+}+6H^{+}⟶{4Fe}^{3+}+{VO}^{2+}+3H_{2}O$
• D. None of these

Answer 1

The correct option is A ${VO}_4^{3-}+{Fe}^{2+}+6H^{+}⟶{Fe}^{3+}+{VO}^{2+}+3H_{2}O$

The unbalanced redox reaction is as follows:
${VO}_4^{3-}+{Fe}^{2+}⟶{Fe}^{3+}+{VO}^{2+}$
All atoms other than H and O are balanced.
The oxidation number of V changes from +5 to +4. The net change in the oxidation number is 1.
The oxidation number of iron changes from +2 to +3. The net change in the oxidation number is 1.
To balance O atoms, add 3 water molecules on RHS.
${VO}_4^{3-}+{Fe}^{2+}⟶{Fe}^{3+}+{VO}^{2+}+3H_{2}O$
To balance H atoms, add 6 $H^{+}$ ions on LHS
${VO}_4^{3-}+{Fe}^{2+}+6H^{+}⟶{Fe}^{3+}+{VO}^{2+}+3H_{2}O$
This is balanced redox reaction in acidic medium.