Question

${\text{C}}{{\text{l}}_{\text{2}}}$ gas is obtained by various reactions but not by:
A. ${\text{KMn}}{{\text{O}}_{\text{4}}}\,\,{\text{ + }}\,{\text{conc}}{\text{.}}\,{\text{HCl}}\,\,\mathop \to \limits^\Delta \,$
B. ${\text{KCl}}\,{\text{ + }}\,{{\text{K}}_2}{\text{C}}{{\text{r}}_2}{{\text{O}}_7}\,\,{\text{ + }}\,{\text{conc}}{\text{.}}\,{{\text{H}}_2}{\text{S}}{{\text{O}}_4}\,\,\mathop \to \limits^\Delta \,$
C. ${\text{Mn}}{{\text{O}}_2}\,\,{\text{ + }}\,{\text{conc}}{\text{.}}\,{\text{HCl}}\,\,\mathop \to \limits^\Delta \,$
D. ${\text{KCl}}\,\,{\text{ + }}\,{{\text{F}}_2}\,\, \to $

Answer 1

Hint: The potassium chromate forms chromyl chloride. Due to the formation of chromyl chloride, chlorine gas does not produce. Let us discuss all the reactions one by one.

Complete step by step answer:
The potassium permanganate is heated with concentrated hydrochloric acid to give potassium chloride, manganese chloride, water and chlorine gas.
The reaction of potassium permanganate with concentrated hydrochloric acid is as follows:
${\text{2}}\,{\text{KMn}}{{\text{O}}_{\text{4}}}\,\,{\text{ + }}\,16\,{\text{conc}}{\text{.}}\,{\text{HCl}}\,\,\mathop \to \limits^\Delta \,2\,{\text{KCl}}\,\,{\text{ + }}\,2\,{\text{MnC}}{{\text{l}}_2}\, + \,8\,{{\text{H}}_{\text{2}}}{\text{O}}\,{\text{ + }}\,{\text{5}}\,{\text{C}}{{\text{l}}_{\text{2}}}$
So, the reaction given in option (A) produces chlorine gas so, option (A) is incorrect.
The potassium chloride, potassium dichromate heated with concentrated sulphuric acid to give potassium sulphate, chromyl chloride and water.
The reaction of potassium chloride, potassium dichromate with concentrated sulphuric acid is as follows:
${\text{4}}\,{\text{KCl}}\,{\text{ + }}\,{{\text{K}}_2}{\text{C}}{{\text{r}}_2}{{\text{O}}_7}\,\,{\text{ + }}\,3\,{\text{conc}}{\text{.}}\,{{\text{H}}_2}{\text{S}}{{\text{O}}_4}\,\,\mathop \to \limits^\Delta \,3\,{{\text{K}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}\, + 2{\text{Cr}}{{\text{O}}_{\text{2}}}{\text{C}}{{\text{l}}_{\text{2}}}\, + 3\,{{\text{H}}_2}{\text{O}}$
The reaction given in option (B) does not produce chlorine gas so, option (B) is correct.
The manganese oxide is heated with concentrated hydrochloric acid to give manganese chloride, chlorine gas and water.
The reaction of manganese oxide with concentrated hydrochloric acid is as follows:
${\text{Mn}}{{\text{O}}_2}\,\,{\text{ + }}\,4\,{\text{conc}}{\text{.}}\,{\text{HCl}}\,\,\mathop \to \limits^\Delta \,{\text{MnC}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,2\,{\text{C}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}$
The reaction given in option (C) produces chlorine gas, so option (C) is incorrect.
The potassium chloride reacts with fluorine to give potassium fluoride and chlorine gas.
The reaction of potassium chloride with fluorine is as follows:
${\text{2}}\,{\text{KCl}}\,\,{\text{ + }}\,{{\text{F}}_2}\,\, \to \,{\text{2}}\,{\text{KF}}\,{\text{ + }}\,{\text{C}}{{\text{l}}_{\text{2}}}$
The reaction given in option (D) produces chlorine gas so, option (D) is incorrect.

So, the correct answer is “Option B”

Note: Potassium permanganate, manganese oxide, and potassium dichromate all are an oxidizing agent but potassium permanganate, and potassium dichromate are very strong. Potassium permanganate and manganese oxide release chlorine gas on reacting with strong acids that have chlorine. But potassium dichromate does not release chlorine gas on reacting with the compound having chlorine due to the formation of chromyl chloride which traps the chlorine.