Question

A gas which bleaches substances by reduction process is:

• A. moist ${Cl}_2$
• B. $S{O}_2$
• C. $O_3$
• D. Dry ${Cl}_2$

Answer 1

The correct option is B $S{O}_2$

Sulphur dioxide is good bleaching agents. Bleaching action of sulphur dioxide is based on reduction.

Sulphour dioxide removes oxygen from the coloured substance and makes it colourless. But atmospheric oxygen slowly takes place of the removed oxygen and because of which the material regains the colour.

Hence option B is correct.