Hydrogen Peroxide
Hydrogen Peroxide (H₂O₂)
Hydrogen peroxide is a chemical compound with the formula H₂O₂. It is the simplest peroxide (a compound with an oxygen-oxygen single bond). It is a colorless liquid at room temperature and is slightly more viscous than water. Hydrogen peroxide is a strong oxidizing agent and is used in various applications, from disinfection to bleaching.
Properties of Hydrogen Peroxide
| Property | Description |
|---|---|
| Molecular Formula | H₂O₂ |
| Molar Mass | 34.0147 g/mol |
| Appearance | Colorless liquid |
| Density | 1.450 g/cm³ (20 °C, 30% (w/w) solution) |
| Melting Point | -0.43 °C (31.23 °F; 272.72 K) |
| Boiling Point | 150.2 °C (302.4 °F; 423.3 K) (decomposes) |
| Solubility in Water | Miscible |
| pH | Approximately 4.5 for a 1% solution |
Hydrogen peroxide is a weak acid, forming hydroperoxide or peroxide salts with many metals.
Chemical Structure
The chemical structure of hydrogen peroxide is as follows:
H
|
O-O
|
H
The O-O bond length is approximately 147.4 pm and the H-O-O angle is 94.8 degrees.
Preparation
Hydrogen peroxide is most commonly produced by the anthraquinone process, which involves the reduction of anthraquinone to hydroquinone, followed by its reaction with oxygen. The overall reaction can be represented as:
$$\text{C}{14}\text{H}{8}\text{O}{2} + \text{H}{2} \rightarrow \text{C}{14}\text{H}{8}\text{O}{2}\text{H}{2}$$ $$\text{C}{14}\text{H}{8}\text{O}{2}\text{H}{2} + \text{O}{2} \rightarrow \text{C}{14}\text{H}{8}\text{O}{2} + \text{H}{2}\text{O}{2}$$
Uses of Hydrogen Peroxide
Hydrogen peroxide has a wide range of applications, including:
- Disinfectant: It is used as a disinfectant in healthcare, in homes, and in the food industry because it kills bacteria, viruses, and fungi upon contact.
- Bleaching Agent: In the textile and paper industries, it is used to bleach cotton and wood pulp.
- Antiseptic: In low concentrations, it is used as an antiseptic in wound care.
- Chemical Synthesis: It is used as a reagent for oxidation reactions in the synthesis of various chemicals.
- Environmental Control: It is used to treat wastewater and to detoxify pollutants.
Reactions
Decomposition
Hydrogen peroxide decomposes into water and oxygen gas, which can be catalyzed by various substances, including transition metals and enzymes like catalase:
$$2\text{H}{2}\text{O}{2} \rightarrow 2\text{H}{2}\text{O} + \text{O}{2}$$
Redox Reactions
As an oxidizing agent, hydrogen peroxide can participate in a variety of redox reactions. For example, it can oxidize iodide ions to iodine in an acidic solution:
$$\text{H}{2}\text{O}{2} + 2\text{I}^{-} + 2\text{H}^{+} \rightarrow \text{I}{2} + 2\text{H}{2}\text{O}$$
Disproportionation
Hydrogen peroxide can act as both an oxidizing and a reducing agent in disproportionation reactions. For instance, in the presence of a base, it can disproportion to form water and oxygen:
$$2\text{H}{2}\text{O}{2} \rightarrow 2\text{H}{2}\text{O} + \text{O}{2}$$
Safety and Storage
Hydrogen peroxide can be dangerous at high concentrations. It is corrosive to the skin, eyes, and respiratory system. It should be stored in a cool, dark place in a container with a vented cap to allow the release of oxygen as it slowly decomposes.
Examples
Disinfection
Hydrogen peroxide is used in hospitals to sterilize surgical instruments and surfaces. A typical concentration for disinfection purposes is 3%.
Bleaching
In the paper industry, hydrogen peroxide is used to bleach paper pulp to a high level of whiteness. Concentrations used for bleaching can range from 35% to 50%.
Antiseptic
For wound care, a dilute solution of hydrogen peroxide (usually 3%) can be applied to minor cuts and abrasions to prevent infection.
Chemical Synthesis
In organic chemistry, hydrogen peroxide can be used to synthesize epoxides, which are important intermediates in the production of various pharmaceuticals.
In summary, hydrogen peroxide is a versatile compound with a wide range of applications due to its oxidizing properties. It is important to handle it with care due to its potential hazards, especially at high concentrations.