Describe Sulphur (IV) oxide as bleaching agent.

Describe Sulphur (IV) oxide as bleaching agent.

Answers

Procedure
- Coloured flower petals are placed in a test-tube full of sulphur (IV) oxide.

Observation
- The coloured (blue or red) petals are bleached (turned colorless);

Explanations:
- In presence of water, sulphur (IV) oxide acts as a bleaching agent. It bleaches by reduction (removal of oxygen form the dye)
- It first combines with water forming the sulphurous acid; which then reduces the dye to form a colourless product.



Note
- The original colour may be restored by oxidation or prolonged exposure to air. This explains why old newspapers which were originally bleached white by sulphur (IV) oxide turn brown with time.
- Chlorine bleaches by oxidation hence its oxidation is permanent; SO₂ is however preferred because it is milder in action.

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Kavungya answered the question on April 29, 2019 at 13:16

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