Explain the reactions of aluminium with acids.

Explanation

Reactions of .Al. with acids :
i) Dil: (or) conc. HCl dissolves Al and gives `H_2`.
`2Al + underset("dil or conc.")(6HCl) to 2AlCl_3 + 3H_2 uarr`
ii) a) Dil. `H_2 SO_4` liberates `H_2`
`underset("(dil)")(2Al + 3H_2 SO_4) to Al_2 (SO_4)_3 + 3H_2 uarr`
b) Conc. `H_2 SO_4` dissolves the metal .Al. and gives `SO_2`
`underset("(Conc.)")(2Al + 6H_2 SO_4) to Al_2 (SO_4)_3 + 6H_2 O + 3SO_2`
iii) a) very dil. `HNO_3` is reduced to `NH_4 NO_3` by Al.
`underset("(dil.)")(8Al + 30HNO_3) to 8Al (NO_3)_3 + 3NH_4 NO_3 + 9H_2 O`
b) Conc. `HNO_3` makes .Al. passive due to the formation of a thin film of oxide layer on the metal surface.