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Explain why conc. HNO3 can be stored in aluminium container

Dear student!

Actually, the nitric acid (HNO3) reacts with aluminium to form a thin protective aluminium oxide (Al2O3) layer on the aluminium surface.  This oxide layer renders aluminium passive and prevents it to further react or dissolve in HNO3 and thus the conc. nitric acid is not affected by the container.

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These containers usually have a plastic coating covering the entire inside.The Al2O3 coatings WILL dissolve in concentrations of aqueous Nitric acid more dilute than about 90% HNO3.Al2O3 (s) + 6 HNO3 (aq) --- 2 Al(NO3)3 (aq) + 3 H2OConcentrations above 90% HNO3 are so strongly oxidizing that they do not react with the Aluminum oxide coating. Aluminum storage tanks for industrial sites have been used, but do have problems when cleaning for inspection.

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