Question

How is chlorine prepared in the laboratory? Explain how it reacts with the following along equations:
a. Hot, Conc.$\,{\text{NaOH}}$
b. ${\text{N}}{{\text{H}}_{\text{3}}}$ excess
c. ${\text{N}}{{\text{a}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{3}}}$

Answer 1

Hint: Chlorine can be prepared in the laboratory by taking hydrochloric acid with oxide. The hydrochloric acid can be replaced with the salt of chloride and strong acid.

Complete step by step answer:
Chlorine can be prepared in the laboratory by taking conc. Hydrochloric acid with manganese dioxide.
The reaction of conc. Hydrochloric acid with manganese dioxide gives manganese di chloride, chlorine gas and water.
The reaction of conc. Hydrochloric acid with manganese dioxide is as follows:
${\text{Mn}}{{\text{O}}_{\text{2}}}\,{\text{ + }}\,{\text{HCl}}\, \to {\text{MnC}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{\text{C}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{\text{2}}{{\text{H}}_{\text{2}}}{\text{O}}\,$
(a) The reaction of chlorine with Hot, Conc.$\,{\text{NaOH}}$ is as follows:
Chlorine on reacting with hot concentrated alkalis hydroxides give chloride and chlorate.
The equation is as follows:
${\text{6}}\,{\text{NaOH}} + 3\,{\text{C}}{{\text{l}}_{\text{2}}} \to 5\,{\text{NaCl}}\,{\text{ + }}\,{\text{NaCl}}{{\text{O}}_{\text{3}}}\,{\text{ + }}\,{\text{3}}{{\text{H}}_{\text{2}}}{\text{O}}\,$
(b) The reaction of chlorine with ${\text{N}}{{\text{H}}_{\text{3}}}$ excess is as follows:
Chlorine on reacting with ${\text{N}}{{\text{H}}_{\text{3}}}$ which is present in excess gives nitrogen and ammonium chloride.
The equation is as follows:
${\text{8}}\mathop {{\text{N}}{{\text{H}}_{\text{3}}}}\limits_{{\text{excess}}} + 3\,{\text{C}}{{\text{l}}_{\text{2}}} \to {{\text{N}}_2}\,{\text{ + }}\,6\,{\text{N}}{{\text{H}}_4}{\text{Cl}}$
(c) The reaction of chlorine with ${\text{N}}{{\text{a}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{3}}}$ is as follows:
Chlorine on reacting with sodium thiosulphate ${\text{N}}{{\text{a}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{3}}}$ give hydrochloric acid, sulphur and sodium sulphate.

The equation is as follows:
${\text{N}}{{\text{a}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{3}}}{\text{ + C}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{S}}\,{\text{ + }}\,2\,{\text{HCl}}\,\,{\text{ + }}\,\,{\text{N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4}$

Note: 

> In the laboratory preparation of chlorine, a salt of chloride and strong acid can be used in place of hydrochloric acid. 

The equation is as follows:
${\text{Mn}}{{\text{O}}_{\text{2}}}\,{\text{ + }}\,{\text{4}}\,{\text{NaCl}}\,\, + \,4\,{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}} \to {\text{MnC}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{\text{C}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{\text{4}}\,{\text{NaHS}}{{\text{O}}_4}{\text{ + }}\,{\text{2}}{{\text{H}}_{\text{2}}}{\text{O}}\,$
> When chlorine reacts with cold and dilute alkalis hydroxides in place of hot concentrated alkalis hydroxides, the reaction gives chloride and hypochlorite.
The equation is as follows:
${\text{2}}\,{\text{NaOH}} + {\text{C}}{{\text{l}}_{\text{2}}} \to \,{\text{NaCl}}\,\,{\text{ + }}\,\,{\text{NaOCl}}\,\,{\text{ + }}\,\,{{\text{H}}_{\text{2}}}{\text{O}}\,$
> When chlorine reacts with ${\text{N}}{{\text{H}}_{\text{3}}}$, if chlorine is in excess in place of ammonia, the reaction gives nitrogen trichloride and hydrochloric acid.
The equation is as follows:
${\text{N}}{{\text{H}}_{\text{3}}} + 3\mathop {{\text{C}}{{\text{l}}_{\text{2}}}}\limits_{{\text{excess}}} \, \to {\text{NC}}{{\text{l}}_3}\,{\text{ + }}\,3\,{\text{HCl}}$