Question

When metal X reacts with dilute $\text{HCl}$, bubbles of gas Y are formed. Moreover, when this metal X reacts with cold water, it will again produce gas Y. Identify X and Y.

Answer 1

Metals on reaction with acids, produce metal salts and hydrogen gas except copper, gold etc.

When sodium reacts with dilute $\text{HCl}$ it forms sodium chloride and hydrogen gas. The reaction involved is:
$\text{2Na(s) + 2HCl(g)}\to {\text{2NaCl(s) + H}}_2\text{(g)}$

Moreover, when it reacts with the cold water it will form sodium hydroxide and hydrogen gas. The hydrogen gas formed immediately catches fire because this reaction generates a lot of heat.

${\text{2Na(s) + H}}_2\text{O(l)}\to {\text{2NaOH(aq) +H}}_2\text{(g)}$

So, X is sodium and Y is hydrogen.