Question

Chlorine acts as a bleaching agent only in the presence of
A. Oxygen
B. Sunlight
C. Air
D. Moisture

Answer 1

Hint: Chlorine is highly used as a bleaching agent, for sterilisation and for preparation of antiseptic. In this process, a nascent oxygen is released on reaction of chlorine, which helps in the bleaching.

Complete Step by Step Answer:
Chlorine is a halogen element.
The chemical formula of bleaching powder is $Ca(OCl)Cl$ . Thus it is evident that bleaching powder contains chlorine. Chlorine can bleach colored substances and make the substances colourless.

Chlorine gas in reaction with moisture that is water produces hydrochloric acid and $HClO$ . This $HClO$ on decomposition gives hydrochloric acid and nascent oxygen. This nascent oxygen can make colored substances colourless and helps in bleaching. Thus the reaction is given as follows:
$C{{l}_{2}}+{{H}_{2}}O\to HCl+HClO\to HCl+[O]$

Thus we can write that chlorine acts as a bleaching agent only in the presence of moisture.
Thus the correct option is D.

Note: Chlorine is the major constituent of sodium hypochlorite and bleaching powder i.e. Ca(OCl)Cl. Sodium hypochlorite is also used as a bleaching agent especially in biological laboratories for the purpose of keeping the equipments germ free.