Question

What happens when gas obtained by heating oxalic acid in presence of sulphuric acid is passed through heated caustic soda

Answer 1

 (COOH)2. 2H2O + conc. H2SO4 + ∆ → CO + CO2 + [H2SO4.3H2O]

Carbon monoxide is prepared by the dehydration of oxalic acid crystal.

Answer 2

Explanation:

When oxalic acid is heated in the presence of concentrated sulphuric acid, oxalic acid dehydrates or in other words, it loses its water molecules.  

$(COOH)_2.2H_2O + conc. H_2SO_4 + heat \rightarrow CO + CO_2 + [H_2SO_4.H_2O]$

The gases so obtained are CO and $CO_2$. When the gases CO and CO2 are passed through caustic soda which is NaOH, CO being soluble, passes through and does not get absorbed and react with NaOH. $CO_2$ on the other hand, is not soluble and gets absorbed and reacts with NaOH to form sodium carbonate $(Na_2CO_3)$.