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Chlorine and Bleach terminology

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Terminology alert: Sometimes people use the same word to describe different things. For example, “chlorine” can refer to:


a single, neutral, chlorine atom. These are unstable.
We normally never encounter one.
They almost instantly bind to each other to form chlorine molecules.


molecule (Cl2) – deadly gas


A chlorine ion is chlorine atom that has picked up an extra electron.
In small quantities these ions are essential for life.


There are many chemicals used to bleach laundry, or disinfect swimming pools.
The most common is “chlorine bleach”, sodium hypochlorite.
Chemical formula is NaOCl
In water this breaks down into a sodium cation (Na+) and a hypochlorite anion (OCl
or ClO− ).

Visualizing the electron distribution in sodium hypochlorite a little more accurately.

How to make sodium hypochlorite

Add chlorine gas (Cl2) to caustic soda (NaOH).

Then sodium hypochlorite, water (H2O) and salt (NaCl) are produced according to the following reaction:

Cl2 + 2NaOH + → NaOCl + NaCl + H2O

How does sodium hypochlorite disinfection work?

By adding hypochlorite to water, hypochlorous acid (HOCl) is formed:

NaOCl + H2O → HOCl + NaOH

Hypochlorous acid is divided into hydrochloric acid (HCl) and oxygen (O).

Sodium hypochlorite is effective against bacteria, viruses and fungi.

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