Difference Between Sodium Chlorite and Sodium Hypochlorite

Key Difference – Sodium Chlorite vs Sodium Hypochlorite
 

Sodium chlorite and sodium hypochlorite are common sodium salts used in industries. Both these compounds are very important as bleaching agents and disinfectants. But they are very different from each other when their chemical properties such as molar mass and physical properties are considered. Sodium chlorite is mainly used in paper manufacturing and as a disinfectant. Sodium hypochlorite is used as a disinfectant by dissolving it in water to form “liquid bleach”. The key difference between sodium chlorite and sodium hypochlorite is that sodium chlorite contains chlorine atoms having +3 oxidation state whereas sodium hypochlorite contains chlorine atoms having +1 oxidation state.

CONTENTS

1. Overview and Key Difference
2. What is Sodium Chlorite
3. What is Sodium Hypochlorite
4. Similarities Between Sodium Chlorite and Sodium Hypochlorite
5. Side by Side Comparison – Sodium Chlorite vs Sodium Hypochlorite in Tabular Form
6. Summary

What is Sodium Chlorite?

Sodium chlorite is an inorganic chemical compound having the chemical formula NaClO₂. The molar mass of this compound is 90.438 g/mol when it is anhydrous. There is a hydrate form as well (composed of three water molecules associated with the sodium chlorite molecule whose molar mass is 144.48 g/mol). The compound is also called chlorous acid. It is an ionic compound that contains a sodium cation (Na⁺) and chlorite anion (ClO₂^–).

It is available as a white crystalline powder which is odorless. The burning of sodium chlorite is difficult, but it can accelerate the burning of organic compounds. Therefore, sodium chlorite can be used to make explosive mixtures with combustible materials. Sodium chlorite decomposes at about 180-200◦C.

Sodium chlorite is less soluble in water but more soluble in methanol and ethanol. The crystal structure of the compound is monoclinic. Sodium chlorite is mainly used in the manufacturing of paper and also as a disinfectant. It is a good oxidizing agent; hence is used to bleach various types of materials such as wood, oils, etc.

The free chlorous acid (HClO₂) is very unstable and it has no considerable importance in industries. But the sodium salt of this acid is very stable and also inexpensive. Most of the times, sodium chlorite is derived from sodium chlorate, which has the chemical formula NaClO₃. The production process is an indirect method in which chlorine dioxide (ClO₂) is produced at first. Chlorine dioxide is very explosive and it is made by reducing sodium chlorate in a strong acid in the presence of a reducing agent like sodium sulfite. The produced chlorine dioxide is then absorbed to an alkaline solution along with reduction by hydrogen peroxide (H₂O₂). This yields sodium chlorite.

What is Sodium Hypochlorite?

Sodium hypochlorite is an inorganic compound having the chemical formula NaClO. The atomic ratio between sodium, chlorine and oxygen is 1:1:1. The compound is composed of a sodium cation bound to a hypochlorite anion. Therefore it is the sodium salt of hypochlorous acid. When sodium hypochlorite is dissolved in water, it is known as liquid bleach due to its bleaching properties.

The molar mass of sodium hypochlorite is 74.44 g/mol. The appearance of this compound can be described as a greenish yellow solid. It also has a sweet odor. The melting point of sodium hypochlorite is 18°C and the boiling point is 101◦C.

Sodium hypochlorite is mainly used as a disinfectant and as a bleaching agent. Almost all the bleaching liquid we use in household contain around 3-8% of sodium hypochlorite. This compound has de-staining properties; hence it is used to remove mold stains, dental stains, etc. Sodium hypochlorite is a good disinfectant since it has a broad range of anti-microbial activity.

The production of sodium hypochlorite is done via Hooker process. It is a large-scale, industrial method. Here, sodium hypochlorite is produced by passing chlorine gas into a cold, dilute sodium hydroxide solution. The other product that is given by this method is sodium chloride (NaCl).

What are the Similarities Between Sodium Chlorite and Sodium Hypochlorite?

• Sodium Chlorite and Sodium Hypochlorite are composed of Na, Cl and O atoms.
• Both are good disinfectants.

What is the Difference Between Sodium Chlorite and Sodium Hypochlorite?

Summary – Sodium Chlorite vs Sodium Hypochlorite

Sodium chlorite is NaClO₂ and sodium hypochlorite is NaClO. The key difference between Sodium chlorite and sodium hypochlorite is that sodium chlorite contains chlorine atoms having +3 oxidations state whereas sodium hypochlorite contains chlorine atoms having +1 oxidations state.

Reference:

1. “Sodium hypochlorite.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. Croswell, Jonathan. “What Is Sodium Chlorite?” LIVESTRONG.COM, Leaf Group, 3 Oct. 2017, Available here.
3. “Sodium hypochlorite.” Wikipedia, Wikimedia Foundation, 17 Feb. 2018, Available here.

Image Courtesy:

1. “Sodium chlorite 450g” By W. Oelen –  (CC BY-SA 3.0) via Commons Wikimedia
2. “Sodium-hypochlorite” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia