Question

Write a balanced half-reaction for the oxidation of liquid water H2O to aqueous hydrogen peroxide H2O2 in basic aqueous solution. Be sure to add physical state symbols where appropriate.

Answer 1

Answer : The balanced half-reaction in a basic solution will be,

$2OH^-(aq)\rightarrow H_2O_2(aq)+2e^-$  

Explanation :

Redox reaction or Oxidation-reduction reaction : It is defined as the reaction in which the oxidation and reduction reaction takes place simultaneously.

Rules for the balanced chemical equation in basic solution are :

First we have to write into the two half-reactions.

Now balance the main atoms in the reaction.

Now balance the hydrogen and oxygen atoms on both the sides of the reaction.

If the oxygen atoms are not balanced on both the sides then adding water molecules at that side where the more number of oxygen are present.

If the hydrogen atoms are not balanced on both the sides then adding hydroxide ion $(OH^-)$ at that side where the less number of hydrogen are present.

Now balance the charge.

• The half reaction is :

$H_2O(l)\rightarrow H_2O_2(aq)$

• Now balance the oxygen atoms.

$H_2O(l)\rightarrow H_2O_2(aq)+H_2O(l)$

• Now balance the hydrogen atoms.

$H_2O(l)+2OH^-(aq)\rightarrow H_2O_2(aq)+H_2O(l)$

• Now balance the charge.

$H_2O(l)+2OH^-(aq)\rightarrow H_2O_2(aq)+H_2O(l)+2e^-$

The balanced half-reaction in a basic solution will be,

$2OH^-(aq)\rightarrow H_2O_2(aq)+2e^-$