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JAMB Chemistry 2012 Paper

Question : 31

Total: 45

Commercial bleaching can be carried out using

sulphur (IV) oxide and ammonia
hydrogen sulphide and chlorine
chlorine and sulphur (IV) oxide
ammonia and chlorine

Solution:

Concept:

Commercial bleaching usually uses agents that remove colour either by oxidation or reduction; chlorine and sulphur(IV) oxide are common bleaching agents.

Explanation:

Chlorine bleaches in the presence of moisture by oxidation:

\mathrm{Cl_2 + H_2O \to HOCl + HCl}

The

\mathrm{HOCl}

produced releases oxygen, which destroys coloured materials.

Sulphur(IV) oxide,

\mathrm{SO_2}

, bleaches by reduction in the presence of moisture.

Ammonia and hydrogen sulphide are not commercially used for bleaching.

Answer:

C. chlorine and sulphur (IV) oxide

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