Question

Explain the following with proper reason:
Dry chlorine does not bleach clothes.

Answer 1

Chlorine acts as a bleaching agent only in the presence of moisture. Chlorine reacts with water to form HOCl and HCl. HOCl is unstable so it decomposes to give nascent oxygen, due to nascent oxygen, chlorine bleaches by oxidation. Nascent oxygen is the oxygen that has just been made in the chemical reaction.

Complete Step By Step Solution
A bleaching agent is a material that lightens a substance through chemical reaction. The bleaching reactions mostly involve oxidative or reductive processes that degrade the color of systems.
Clothes can be bleached by the oxidation process but for that we require nascent oxygen. Chlorine cannot produce nascent oxygen in the absence of water so this is the reason that dry chlorine is not able to produce nascent oxygen required for oxidation and so it is not able to bleach clothes. $\begin{aligned} & C {{l}_{2}} + {{H}_{2}} O\to HClO + HCl \\\ & HClO\to HCl + O \\\ \end{aligned}$
In the above given reaction HClO is produced on reaction of chlorine with water and this HClO produced is unstable so it further produces HCl and nascent oxygen which undergoes oxidation and bleaches the clothes. So, without water no HClO is produced therefore no nascent O and no bleaching.

Additional Information
Bleaching agents are chemicals that oxidize or reduce impurities and colorants in the material which is to be bleached. Sun exposure has been used since ancient times to reduce the impurities. Bleaching agents can produce harmful effects on skin as they can cause irritation due to the presence of acids.
Oxidation is defined as the chemical process in which a substance gains oxygen or loses electrons and hydrogen. When one of the reactants is oxygen, then oxidation is the gain of oxygen. Reduction is the loss of oxygen. The nascent oxygen reacts easily with the chromophores(part of the molecule responsible for color) to remove electrons from the molecule, which chemically changes the structure of the molecule and the physical properties that cause the color. This is how nascent oxygen helps in bleaching by the oxidation process.

Note
Main types of bleaching agents are chlorine and its related compounds (such as sodium hypochlorite) and the per-oxygen bleaching agents. Nascent oxygen is the oxygen which hasn’t bonded covalently with another oxygen atom to form ${{O}_{2}}$ . It is the monatomic oxygen which is very reactive and very unstable. It has a high tendency to react with other nascent oxygen to form oxygen molecules.