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Chlorite

physical science Maturity 11-13 Next article →

The chlorite ion is a specific chemical group known as the chlorine dioxide anion. It has the chemical formula ClO2-.

Hypochlorite-3D-vdW
Hypochlorite-3D-vdW

This ion is a member of a larger family of chlorine oxides. These are substances where chlorine and oxygen are bonded together. Chlorites are also described as salts of chlorous acid. This group of chemicals is important because of how they interact with other substances. Specifically, chlorite is a very strong oxidiser. An oxidiser is a substance that causes a chemical change in others through a specific reaction.

Chloride-ion-3D-vdW
Chloride-ion-3D-vdW

To understand how chlorite works, we must look at its molecular geometry. The ion has a bent shape rather than a straight line. This occurs because of the effects of lone pairs on the chlorine atom. Lone pairs are groups of electrons that do not participate in bonding. These pairs push the other atoms away, creating a specific angle. The O–Cl–O bond angle is exactly 111 degrees. Additionally, the Cl–O bond lengths are 156 pm.

Hypochlorite-3D-vdW
Hypochlorite-3D-vdW

This structure defines how the ion behaves in chemical reactions.

Chlorite belongs to a series of oxyanions. These are ions containing oxygen and a central atom. In this family, chlorine can exist in several different oxidation states. An oxidation state is a way to describe the charge on an atom. The different states include -1, +1, +3, +5, and +7. Each state creates a different ion with a unique name. For example, chloride has an oxidation state of -1. Hypochlorite has a state of +1. Chlorite is the +3 state. Chlorate is +5, and perchlorate is +7.

Chlorate-3D-vdW
Chlorate-3D-vdW

There are many different types of chlorite compounds. Most alkali metal and alkaline earth metal compounds are colorless or pale yellow. Sodium chlorite (NaClO2) is the most commercially important version. Other compounds involve heavy metals such as silver, mercury, thallium, lead, copper, or iron. These heavy metal chlorites are quite unstable. They can decompose explosively if they are exposed to heat or shock. The free acid, chlorous acid (HClO2), is also very unstable. It can only be observed as an aqueous solution at low concentrations. Because it cannot be concentrated, it is not used as a commercial product.

Sodium chlorite is used widely in industrial processes. Its primary use is in the bleaching of textiles, pulp, and paper. However, it is often not used directly in its own form. Instead, it is used to generate a neutral species called chlorine dioxide (ClO2). This is achieved through a reaction with hydrochloric acid (HCl). The chemical equation for this process is 5 NaClO2 + 4 HCl → 5 NaCl + 4 ClO2 + 2 H2O. This reaction produces salt, water, and the useful chlorine dioxide.

Chlorate-3D-vdW
Chlorate-3D-vdW

Safety and health regulations are very important when dealing with chlorite. In 2009, the California Office of Environmental Health Hazard Assessment (OEHHA) set a public health goal. They recommended maintaining chlorite levels in drinking water below 50 parts per billion. This is a very small amount. Some scientific studies have indicated that chlorite may be carcinogenic at certain levels. A carcinogen is a substance that can cause cancer. The federal legal limit in the United States is different. It allows up to 1,000 parts per billion in drinking water. This federal limit is 20 times higher than the California goal.

Chlorite is also notable for its strength as an oxidiser. When looking at the standard half-cell potentials, it is the strongest oxidiser among the chlorine oxyanions. This potential measures how much a substance wants to gain electrons. In acidic reactions, chlorite has an E° of 1.64 V. This is higher than hypochlorite at 1.63 V and chlorate at 1.47 V. In neutral or basic reactions, chlorite has an E° of 0.78 V. This makes it a very active participant in chemical environments. Understanding these values helps scientists predict how chlorite will react with other chemicals.

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File:Hypochlorite-3D-vdW.png
Hypochlorite-3D-vdW.png
File:Chlorite-3D-vdW.png
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File:Chlorate-3D-vdW.png
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File:Perchlorate-3D-vdW.png
Perchlorate-3D-vdW.png
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