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, reaction does not proceed. Explain the reason.

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alok kumar singh | Contributor-Level 10

5 months ago

This is a Short Answers Type Questions as classified in NCERT Exemplar

The following reaction takes place in the test tube

i) When Aluminium is treated with dilute hydrochloric acid.

Al + HCl -à AlCl₃

ii) When Aluminium is treated with dilute sodium hydroxide solution.

Al + NaOH -àNaAlO₂ + H₂

In both the cases, the Hydrogen atoms are evolved. So, when a burning match stick is brought near the test tube we hear a pop sound.

Aluminium does not react with concentrated nitric acid. A "layer" of "Aluminium Oxide" is formed, when aluminium reacts with the nitric acid because "nitric acid" is an oxidising

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