Chlorine Gas - Cl<sub>2</sub>

What is Chlorine gas?

Chlorine is a green yellow gas with a very pungent odour that is twice as dense as air. It is a chemical element belongs to the halogen group with the symbol Cl. It was discovered in 1770’s and soon became useful as a commercial agent.It is found easily in natural state. It should be handled carefully because it is poisonous at low concentrations. Chlorine is very harmful and been used as chemical weapons throughout history.

Other name – Molecular chlorine

Cl2

Chlorine gas

Density

3.2 g/L

Molecular Weight/ Molar Mass

35.453 u

Boiling Point

-34.04 °C

Melting Point

-101.5 °C

Chemical Formula

Cl2

Chlorine gas Structure – Cl2

Chlorine

Physical Properties of Chlorine gas – Cl2

Odour

Odour of bleach

Appearance

Yellow green gas

Covalently-Bonded Unit

1

Vapour Pressure

85.3 psig

pH

7.4

Solubility

Slightly soluble in water

Chemical Properties of Chlorine gas – Cl2

  • Chlorine reacts with organic compounds and ammonia to form chloro-organics or chloramines. Chloramines are part of the group of chlorine compounds that have disinfectant properties and show up as part of chlorine residue test.
  • It acts as a reducing agent present in wastewater. These reactions are called chlorine demand. The reaction is as below.

    H2O + Cl2 → HCl + HClO

Uses of Chlorine gas – Cl2

  • Chlorine gas was used by the Germans as a chemical weapon against the allied troops during the First World War.
  • The most common use of chlorine in wastewater treatment is for disinfection.
  • Used in odor control and in the control of filamentous organisms in the activated sludge process.
  • Despite of all these it is used for preventing the spread of waterborne disease and the most common means of disinfection in use.

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