Question

Chlorine reacts with hot conc. $NaOH$ giving;
A. $NaCl,NaOCl$
B. $NaCl,NaCl{O_3}$
C. $NaCl,NaCl{O_4}$
D. $NaCl{O_3},NaCl{O_4}$

Answer 1

Chlorine is a reactive gas so it reacts with both hot conc. and cold dilute solution. But here, it will yield two different reactions.

Complete step by step answer
Chlorine was discovered by Scheele by the action of $HCl$ on $Mn{O_2}$. A scientist named Davy explained its elementary nature and provides the name chlorine due to its colour. (Greek, chloros = greenish yellow).
It can be prepared by any one of the following methods:
1. By heating manganese dioxide with concentrated hydrochloric acid.
$Mn{O_2}{\rm{ }} + {\rm{ }}4HCl{\rm{ }} \to {\rm{ }}MnC{l_2}{\rm{ }} + {\rm{ }}C{l_2}{\rm{ }} + {\rm{ }}2{H_2}O$
However, a mixture of common salt and concentrated $H_2SO_4$ is used in place of $HCl$. $4NaCl{\rm{ }} + {\rm{ }}Mn{O_{}}{\rm{ }} + {\rm{ }}4{H_2}S{O_4}{\rm{ }} \to {\rm{ }}MnC{l_2}{\rm{ }} + {\rm{ }}4NaHS{O_4}{\rm{ }} + {\rm{ }}2{H_2}O{\rm{ }} + {\rm{ }}C{l_2}$

2. By the action of HCl on potassium permanganate.
$2KMn{O_4}{\rm{ }} + {\rm{ }}16HCl{\rm{ }} \to {\rm{ }}2KCl{\rm{ }} + {\rm{ }}2MnC{l_2}{\rm{ }} + {\rm{ }}8{H_2}O{\rm{ }} + {\rm{ }}5C{l_2}$

3. Deacon’s process: By oxidation of hydrogen chloride gas by atmospheric oxygen in the presence of $CuC{l_2}$ (catalyst) at $723K$.

4. Electrolytic process: Chlorine is obtained by the electrolysis of brine (concentrated $NaCl$ solution). Chlorine is liberated at anode. It is also obtained as a by–product in many chemical industries.

Chlorine is greenish yellow in colour. It has a very pungent and a suffocating smell. Its solubility is very high and it will react with different metals and non-metals to form chlorides. It has great affinity for hydrogen. It reacts with compounds containing hydrogen to form HCl. Chlorine reacts with hydrocarbons and gives substitution products with saturated hydrocarbons and additional products with unsaturated hydrocarbons. Chlorine water on standing loses its yellow colour due to the formation of HCl and $HOCl$. Hypochlorous acid ($HOCl$) is formed, gives nascent oxygen which is responsible for oxidising and bleaching properties of chlorine.
With hot and concentrated alkali, it gives chloride and chlorate.

$$6{\rm{ }}NaOH{\rm{ }} + {\rm{ }}3C{l_2}{\rm{ }} \to {\rm{ }}5NaCl{\rm{ }} + {\rm{ }}NaCl{O_3} + {\rm{ }}3{H_2}O{\rm{ }}\\\ \left( {hot{\rm{ }}\,and\\\\{\rm{ }}conc.} \right)$$

**Hence, option (B) is correct.

Note **
With cold and dilute alkali, chlorine produces a mixture of chloride and hypochlorite.

$$2NaOH{\rm{ }} + {\rm{ }}C{l_2}{\rm{ }} \to {\rm{ }}NaCl{\rm{ }} + {\rm{ }}NaOCl{\rm{ }} + {\rm{ }}{H_2}O{\rm{ }}\\\ \left( {cold{\rm{ }}\,and\\\\{\rm{ }}dilute} \right){\rm{ }}$$