Hydrogen peroxide can act as either an oxidizing agent or a reducing agent, depe

Question

Hydrogen peroxide can act as either an oxidizing agent or a reducing agent, depending on the species present in solution. Write balanced half-reaction equations for each of the following: (a) H202 aq) acting as an oxidizing agent in an acidic solution. Write the balanced half-reaction equation. Phases are optional. 2H++H2O2 2H2O (b) H202(aq) acting as a reducing agent in an acidic solution. Write the balanced half-reaction equation Phases are optional. (c) A disproportionation reaction is one in which a single species oxidizes and reduces itself. Write the complete balanced equation for the disproportionation reaction of H202(aq). Phases are optional. 2H202 2H2O+02

Explanation / Answer

(a)Oxidising agent in acidic condition:

The oxidation state of each oxygen atom in H2O2 is –1 (see Example 24-1c). Because H2O2(aq) is acting as an oxidizing agent, the oxygen atom is reduced to an oxidation state of –2. This is the lowest possible oxidation state for an oxygen atom because the addition of two electrons yields a noble-gas electron configuration. The oxidation state of the oxygen atom in a water molecule is –2, and so we write

H2O2 H2O (reduction)

Balancing the oxygen atoms by adding another H2O molecule to the right side yields

H2O2 2 H2O

and balancing the hydrogen atoms by adding 2 H+ ions to the left side yields

2 H+ + H2O2 2 H2O

We now balance the charge by adding 2e– to the left side and indicate phases to obtain

2 H+(aq) + H2O2(aq) + 2 e– 2 H2O(l)

(b) Balanced equation for reducing agent in acidic condition:

H2O2(aq) O2(g) + 2 H+(aq) + 2 e–

(c) Disproportionation:

Hg2Cl2 ==> Hg + HgCl2
One Hg atom is oxidized and the other one is reduced.
2H2O2 ==> 2H2O + O2

Ag(s) + 2H+(aq) +2NO3-(aq) --> NO2(g) + H2O(l) + Ag+(aq) + NO3-(aq) that is your net ionic.

2 Cu0 + O20 2 CuIIO-II

Cu0 - 2e- CuII (oxidation)

O0 + 2e- O-II (reduction)

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