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Aluminium dissovles in mineral acids and aqueous alkalies and thus shows amphoteric character. A place of aluminum 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 evolution of hydrogen gas. The same activity when performed with concentrated with concentrated nitric acid. reaction doesn't proceed. Expalin the reason.

Answer» <html><body><p></p>Solution :Aluminium being amphoteric in nature dissolves both in acids and alkalies evolving `H_(2)` gas which burns with a <a href="https://interviewquestions.tuteehub.com/tag/pop-592262" style="font-weight:bold;" target="_blank" title="Click to know more about POP">POP</a> sound <br/> `2Al+6HClrarr2AlCl_(3)+3H_(2)` <br/> `2Al+NaOH+2H_(2)Orarrunderset("Sodium meta aluminate")(2NaAlO_(2))+3H_(2)` <br/> But when Al is <a href="https://interviewquestions.tuteehub.com/tag/treated-1426908" style="font-weight:bold;" target="_blank" title="Click to know more about TREATED">TREATED</a> with conc. `HNO_(3)`, a thin protective layer of `Al_(2)O_(3)` is formed on its <a href="https://interviewquestions.tuteehub.com/tag/surface-1235573" style="font-weight:bold;" target="_blank" title="Click to know more about SURFACE">SURFACE</a> which prevents further action <br/> `2Al + 6HNO_(3) <a href="https://interviewquestions.tuteehub.com/tag/rarr-1175461" style="font-weight:bold;" target="_blank" title="Click to know more about RARR">RARR</a> Al_(2)O_(3)+6NO_(2)+3H_(2)O`.</body></html>


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