Question

Oxalic acid on heating with conc. ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ produce
A. ${{\text{H}}_2}{\text{O}}$and ${\text{C}}{{\text{O}}_2}$
B. ${\text{CO}},\,$ ${\text{C}}{{\text{O}}_2}$and${{\text{H}}_2}{\text{O}}$
C. ${\text{C}}{{\text{O}}_2}$and ${{\text{H}}_2}{\text{S}}$
D. ${\text{CO}}$and ${\text{C}}{{\text{O}}_2}$

Answer 1

Hint: Concentrated sulphuric acid is a strong oxidizing agent and also a dehydrating agent. The dehydrating agent removes water from the compounds.

Complete step by step answer:
Concentrated sulphuric acid works as a dehydrating agent, so it discards water molecules from the compound and thus dehydrates the compound. These reactions are known as dehydration reactions and the substance which causes the dehydration is known as a dehydrating agent.
The chemical formula of oxalic acid is ${\left( {{\text{COOH}}} \right)_2}$. The concentrated sulphuric acid removes water from oxalic acid.
The heating reaction of oxalic acid in presence of concentrated sulphuric acid is as follows:
${\left( {{\text{COOH}}} \right)_2}\, + \,{{\text{H}}_2}{\text{S}}{{\text{O}}_4} + \,{\text{Heat }} \to \,{\text{CO}}\,{\text{(g)}}\,{\text{ + }}\,{\text{C}}{{\text{O}}_2}\,{\text{(g)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}}$
So, heating of oxalic acid in presence of concentrated sulphuric acid produces carbon monoxide gas, carbon dioxide gas, and a water molecule.
The option (A) does not have carbon monoxide gas so the option (A) is incorrect.
Therefore, option (B), ${\text{CO}},\,{\text{C}}{{\text{O}}_2} $and$ {{\text{H}}_2}{\text{O}}$, is correct.
Hydrogen sulfide gas does not produce during the reaction of oxalic acid and concentrated sulphuric acid so option (C) is incorrect.

Therefore, Option B is correct.

Note:
In case of dehydration reaction water forms as one of the products. Concentrated sulphuric acid is a hygroscopic substance that has a high affinity for water molecules, so the presence of sulphuric acid with the heat on the reactant side in reaction indicates dehydration reaction. The presence of only sulphuric acid, no heat can lead to the oxidation reaction where the sulphuric acid acts as an oxidizing agent hence causing the oxidation of a species.