Reactions of Peroxides and Superoxides with Water and Acids

Peroxides and Superoxides: Chemical Reactions

Reactions with Water

Peroxides and superoxides are compounds containing oxygen in unusual oxidation states. Their reactions with water are important in understanding their chemical behavior and applications.

• Peroxides react with water to produce hydroxide ions (OH-) and hydrogen peroxide (H2O2) as an additional product.

• Superoxides produce hydroxide ions (OH-), hydrogen peroxide (H2O2), and oxygen gas (O2) as additional products.

Compound Type	Example Reaction	Products
Peroxides	$\mathrm{BaO_2 (s) + 2 H_2O (l) \rightarrow Ba(OH)_2 (aq) + H_2O_2 (aq)}$	Barium hydroxide, hydrogen peroxide
Superoxides	$\mathrm{2 KO_2 (s) + 2 H_2O (l) \rightarrow 2 KOH (aq) + H_2O_2 (aq) + O_2 (g)}$	Potassium hydroxide, hydrogen peroxide, oxygen gas

• Key Point: Superoxides generate oxygen gas in addition to the products formed by peroxides.

Example: Complete and balance the following equation:

$\mathrm{Na_2O_2 (s) + 2 H_2O (l) \rightarrow 2 NaOH (aq) + H_2O_2 (aq)}$

Practice: Write a balanced equation for the reaction of sodium superoxide with water:

$\mathrm{2 NaO_2 (s) + 2 H_2O (l) \rightarrow 2 NaOH (aq) + H_2O_2 (aq) + O_2 (g)}$

Reactions with Acids

Peroxides and superoxides also react with acids, producing different products compared to their reactions with water.

• Peroxides react with acids to produce hydrogen peroxide (H2O2) instead of water.

• Superoxides produce hydrogen peroxide (H2O2) and oxygen gas (O2) in addition to salts.

Compound Type	Example Reaction	Products
Peroxides	$\mathrm{Na_2O_2 (s) + 2 HCl (aq) \rightarrow 2 NaCl (aq) + H_2O_2 (aq)}$	Sodium chloride, hydrogen peroxide
Superoxides	$\mathrm{2 KO_2 (s) + 2 HCl (aq) \rightarrow 2 KCl (aq) + H_2O_2 (aq) + O_2 (g)}$	Potassium chloride, hydrogen peroxide, oxygen gas

• Key Point: Acidic reactions of superoxides yield oxygen gas, which is not produced in peroxide reactions.

Example: Complete and balance the following reaction:

$\mathrm{2 CaO_2 (s) + H_2SO_4 (aq) \rightarrow CaSO_4 (aq) + H_2O_2 (aq) + O_2 (g)}$

Practice: Write a balanced equation for the reaction of barium peroxide with hydrochloric acid:

$\mathrm{BaO_2 (s) + 2 HCl (aq) \rightarrow BaCl_2 (aq) + H_2O_2 (aq)}$

Definitions and Key Concepts

• Peroxide: A compound containing the O22- ion, where oxygen has an oxidation state of -1.

• Superoxide: A compound containing the O2- ion, where oxygen has an average oxidation state of -1/2.

• Hydrogen Peroxide (H2O2): A common product in both peroxide and superoxide reactions, used as a disinfectant and bleaching agent.

• Oxygen Gas (O2): Produced in superoxide reactions, important for biological and industrial processes.

Applications

• Peroxides and superoxides are used in oxygen generation systems, bleaching, and as oxidizing agents in chemical synthesis.

• Understanding their reactions is important in inorganic chemistry and environmental science.

Additional info: These reactions are relevant to the study of the chemistry of nonmetals and periodic properties, as well as aqueous equilibria and acid-base chemistry.