Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

2.3.4Inorganic Chemistry

Uses of Chlorine and Chlorate(I) — Oxford AQA International A Level Chemistry Revision Notes & Topical Questions

5 min read 5 parts Lesson 12 of 27

📚 Oxford AQA International A Level Chemistry Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read

Part 1 of 5Disproportionation

2.3.4 Uses of Chlorine and Chlorate(I)

A single chlorine atom changes in two directions: part is oxidised, part is reduced.

Disproportionation
Definition
  • Disproportionation is a reaction in which the same element is both oxidised and reduced.
Chlorine and water
  • Cl₂(aq) + H₂O(l) ⇌ HClO(aq) + HCl(aq); chlorine goes from 0 to +1 in chloric(I) acid and to −1 in HCl.
Cold alkali
  • Cl₂(aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H₂O(l), again oxidising chlorine to +1 and reducing it to −1.
Sodium chlorate(I)
  • The solution of NaClO is household bleach, and the active species is the chlorate(I) ion ClO⁻.

Part 2 of 5Water Treatment

Action
  • Chloric(I) acid and chlorate(I) ions are strong oxidising agents and kill bacteria in drinking water and swimming pools.
Benefit
  • Treated water prevents the spread of diseases such as cholera and typhoid.
Risk 1
  • Chlorine gas is toxic and corrosive, so storage and handling need careful safety measures.
Risk 2
  • Chlorine can react with organic matter in water to form chlorinated hydrocarbons, some of which are suspected carcinogens.
Judgement
  • Most public health authorities decide that the benefit of disinfection outweighs the small risks.

Part 3 of 5Bleach and Other Uses

1
Chlorine is bubbled into cold, dilute sodium hydroxide solution to make sodium chlorate(I).
2
The solution contains NaClO, which acts as an oxidising agent and bleaches coloured substances.
3
It is used as a household bleach for cleaning and as a disinfectant.
4
The temperature must be kept low, because warm or hot alkali produces different products.
5
Chlorine is also used to make solvents, plastics such as PVC and many pharmaceuticals.

Part 4 of 5Oxidation State Analysis

Oxidation State Analysis
Cl₂
  • Elemental chlorine has oxidation state 0, since there are no electronegativity differences between the atoms.
ClO⁻
  • In chlorate(I), oxygen is −2 and the ion has charge −1, so chlorine is +1.
Cl⁻
  • Chloride is −1; both ClO⁻ and Cl⁻ come from chlorine, confirming disproportionation.

Part 5 of 5Exam Checklist & Tips

2.3.4 – Key Points for the Exam

  • Disproportionation A redox reaction in which the same element is oxidised and reduced.
  • Chlorate(I) The ion ClO⁻, in which chlorine has oxidation state +1.
  • Disinfectant A substance that kills harmful microorganisms.
  • Bleach A substance that removes colour, often by oxidation.

Common Mistakes

  • Writing the product of chlorine and cold sodium hydroxide as NaClO₃.
  • Saying chlorine is only oxidised in its reaction with water.
  • Stating that chlorine is a reducing agent in water treatment.
  • Ignoring the health risks of chlorine when evaluating its use.

Last updated:

\n