Aluminium dissolves in mineral acids and aqueous alkalis and thus shows amphoteric character. A piece ofaluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning match stick near the mouth of the test tube, a pop sound indicates the evolutionof hydrogen gas. The same activity when performed with concentrated nitric acid, reaction doesn't proceed . Explain the reason.

Aluminium dissolves in mineral acids and aqueous alkalis and thus show

1.	Aluminium dissolves in mineral acids and aqueous alkalis and thus shows amphoteric character. A piece ofaluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning match stick near the mouth of the test tube, a pop sound indicates the evolutionof hydrogen gas. The same activity when performed with concentrated nitric acid, reaction doesn't proceed . Explain the reason.
Answer» Solution :Aluminum is amphoteric in nature ,it reacts with acid and base to give salt and `H_2` gas. It burns with POP SOUND . `2Al+6HCl to 2AlCl_3 + 3H_2` `2Al+NaOH + 2H_2O to 2NaAlO_2 + 3H_2` When Al reacts with conc. `HNO_3` , a THIN layer of `Al_2O_3` on the surface of Al metal which protect further reaction. This layer is CALLED protective layer. `2Al+6HNO_3 to Al_2O_3 + 6NO_2 + 3H_2O`