(N/A) The chemical equation for the reaction is:
$CH_{3}COOH + NaHCO_{3} \rightarrow CH_{3}COONa + H_{2}O + CO_{2}$
$X$ is sodium ethanoate $(CH_{3}COONa)$.
The gas evolved is carbon dioxide $(CO_{2})$.
Activity:
$1$. Take a test tube and add a small amount of sodium hydrogencarbonate $(NaHCO_{3})$ to it.
$2$. Add a few drops of ethanoic acid $(CH_{3}COOH)$ to the test tube.
$3$. You will observe effervescence due to the evolution of a gas.
$4$. Pass this gas through a delivery tube into another test tube containing lime water $(Ca(OH)_{2})$.
$5$. The lime water will turn milky,which confirms that the evolved gas is carbon dioxide $(CO_{2})$.
Chemical reaction with lime water:
$Ca(OH)_{2} + CO_{2} \rightarrow CaCO_{3} + H_{2}O$