Question

Mark the incorrect statement about bleaching action of $C{l}_2$ and $S{O}_2$:

• A. Bleaching of flowers by chlorine is permanent.
• B. After bleaching with $S{O}_2$ the colour of flowers returns.
• C. $C{l}_2$ bleaches coloured material by oxidation.
• D. $S{O}_2$ is reduced when it bleaches coloured material.

Answer 1

The correct option is D $S{O}_2$ is reduced when it bleaches coloured material.

a) The bleaching action of chlorine is based on oxidation. It reacts with water to produce nascent oxygen. This oxygen reacts with coloured substance and thus make it colourless.
b) This is because the bleaching action of $S{O}_2$ is based on reduction. So when the bleached colourless compounds are exposed to air, they will get oxidised again. Hence, after bleaching with $S{O}_2$ the colour of flowers return.
c) As we have explained in option (a), $C{l}_2$ bleaches coloured material by oxidation.
d) Since the bleaching action of $S{O}_2$ is based on reduction, hence $S{O}_2$ itself gets oxidised