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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» <html><body><p></p>Solution :Aluminum is amphoteric in nature ,it reacts with acid and base to give salt and `H_2` gas. It burns with <a href="https://interviewquestions.tuteehub.com/tag/pop-592262" style="font-weight:bold;" target="_blank" title="Click to know more about POP">POP</a> <a href="https://interviewquestions.tuteehub.com/tag/sound-648690" style="font-weight:bold;" target="_blank" title="Click to know more about SOUND">SOUND</a> . <br/> `2Al+6HCl to 2AlCl_3 + 3H_2` <br/> `2Al+NaOH + 2H_2O to 2NaAlO_2 + 3H_2` <br/> When Al reacts with conc. `HNO_3` , a <a href="https://interviewquestions.tuteehub.com/tag/thin-707663" style="font-weight:bold;" target="_blank" title="Click to know more about THIN">THIN</a> layer of `Al_2O_3` on the surface of Al metal which protect further reaction. This layer is <a href="https://interviewquestions.tuteehub.com/tag/called-907796" style="font-weight:bold;" target="_blank" title="Click to know more about CALLED">CALLED</a> protective layer. <br/> `2Al+6HNO_3 to Al_2O_3 + 6NO_2 + 3H_2O`</body></html>


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