Question

Write the reaction of conc. sulphuric acid with oxalic acid.

Hint:

Conc. H$_2$SO$_4$ dehydrates oxalic acid to give CO and CO$_2$ — a key test reaction for distinguishing H$_2$C$_2$O$_4$.

Answer 1

Step 1: Reaction involved.
When concentrated sulphuric acid reacts with oxalic acid (H$_2$C$_2$O$_4$), it acts as a dehydrating agent and also as an oxidizing agent.
Step 2: Chemical equation.
\[ \text{H}_2\text{C}_2\text{O}_4 \xrightarrow[\text{Conc. H}_2\text{SO}_4]{\text{Heat}} \text{CO} + \text{CO}_2 + \text{H}_2\text{O} \] Step 3: Observation.
On heating, a mixture of carbon monoxide (CO) and carbon dioxide (CO$_2$) gases is evolved, and water vapor is released. The reaction mixture becomes warm due to its exothermic nature.
Step 4: Explanation.
Concentrated H$_2$SO$_4$ removes water from oxalic acid and decomposes it into CO and CO$_2$.