Question

Chlorine is liberated when we heat:
A. \[KMn{{O}_{4}}+NaCl\]
B. \[P{{b}_{2}}{{(N{{O}_{3}})}_{4}}+Mn{{O}_{2}}\]
C. \[{{K}_{2}}C{{r}_{2}}{{O}_{7}}+Mn{{O}_{2}}\]
D. \[{{K}_{2}}C{{r}_{2}}{{O}_{7}}+HCl\]

Answer 1

Hint: When a compound is treated with salt of chlorine or hydride of chlorine then only chlorine is liberated. Sodium chloride can’t react with potassium permanganate directly to liberate chlorine gas without sulfuric acid.

Complete Step by Step Answer:
Hydrogen chloride reacts with potassium dichromate to produce a salt of potassium that is potassium chloride along with a salt of chromium that is chromium chloride, water and chlorine gas as products.

Thus the reaction is given as follows:
\[{{K}_{2}}C{{r}_{2}}{{O}_{7}}+14HCl\to 2KCl+2CrC{{l}_{3}}+7{{H}_{2}}O+3C{{l}_{2}}\]

Thus in this reaction fourteen moles of Hydrogen chloride reacts with one mole of potassium dichromate to produce two moles of a salt of potassium that is potassium chloride along with two moles of a salt of chromium that is chromium chloride, seven moles of water and three moles of chlorine gas as products.

Thus chlorine gas is liberated in the reaction of potassium dichromate and hydrogen chloride.
Thus the correct option is D.

Additional Information: Chlorine is a halogen element. It has the symbol of $Cl$. It generally exists as a gas. It has the colour yellow.

Note: Potassium dichromate is a strong oxidising agent. Thus it helps to oxidise another species and reduce itself. In this reaction potassium dichromate oxidises hydrogen chloride to chlorine gas.