Question

A colourless solid (X) on heating evolved CO2 & also gave a white residue , soluble in water.Residue also gave CO2 when treated with dilute acid. So (X) is

Answer 1

sodium chloride may be

Answer 2

Answer : The colourless solid (X) is, sodium bicarbonate $(NaHCO_3)$.

Explanation :

As per question,

When the colourless solid sodium bicarbonate on heating it evolved sodium carbonate residue, water and carbon dioxide gas.

The balanced chemical reaction will be :

$Na_HCO_3(s)\overset{\Delta}\rightarrow Na_2CO_3(s)+H_2O(l)+CO_2(g)$

In this reaction, the residue sodium carbonate is soluble in water.

When the residue sodium carbonate treated with dilute acid like dil. HCl then it gives sodium bicarbonate and sodium chloride as a product.

The balanced chemical reaction will be :

$NaCO_3+HCl\rightarrow NaHCO_3+NaCl$

Hence, the colourless solid (X) is, sodium bicarbonate $(NaHCO_3)$.