Aluminium dissolves in mineral acids and aqueous

Question:

Aluminium dissolves in mineral acids and aqueous alkalies and thus shows amphoteric character. A piece of aluminium foil is treated with dilute hydrochloric

acid or dilute sodium hydroxide solution in a test tube and on bringing a burning matchstick near the mouth of the test tube, a pop sound indicates the evolution

of hydrogen gas. The same activity when performed with concentrated nitric acid, the reaction doesn’t proceed. Explain the reason.

Solution:

Aluminium reacts both with acid and base to give hydrogen gas which burns in air with a pop sound. Nitric acid forms a thin layer of aluminium oxide on the surface of

aluminium as it is a strong oxidizing agent. Thus, the further reaction is prevented and no hydrogen is liberated.

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