The metal X reacts with dilute hydrochloric acid to form a gas Y. The metal X also reacts with sodium hydroxide solution (on heating) to form the same gas Y. When a lighted matchstick is applied, this gas burns by producing a ‘pop’ sound.
(a) name two metals which could behave like X
(b) Name the gas Y
(a) The ‘pop’ sound indicates the presence of hydrogen gas. Metals react with dilute acids to form metallic salts and hydrogen gas. Some metals react with bases to produce hydrogen gas. Generally, non-metals do not react with acids. For example, Aluminium reacts with dilute hydrochloric acid to form Aluminium chloride and hydrogen gas. The balanced chemical equation for the reaction is:
2Al(s) + 6HCl(aq) 
2AlCl3(aq) + 3H2(g).
Aluminium is an amphoteric metal. It reacts with both acids and bases. The reaction is highly exothermic and produces a lot of heat. There is rapid evolution of hydrogen gas during this reaction. Aluminium metal reacts with a base called sodium hydroxide to produce sodium aluminate and hydrogen gas.
(b) The name of the gas is hydrogen.