Name the gas produced when aluminium foil reacts with:
(a) dilute hydrochloric acid.
(b) Sodium Hydroxide solution.

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.

(a) Metals react with dilute acids to form metallic salts and hydrogen gas. 

Aluminium foil reacts with dilute hydrochloric acid to produce aluminium chloride and hydrogen gas.

The balanced chemical equation for the reaction is:

$2Al(s) + 6HCl(aq) \rightarrow 2AlCl_3(aq) + 3H_2(g)$

(b) When aluminium foil reacts with sodium hydroxide, sodium aluminate is formed.