Question

A small piece of aluminium metal was placed in a beaker containing a greenish solution. After some time, a grey coating was observed on the aluminium piece. The greenish solution is most likely to be :
(1) salt solution of copper metal
(2) salt solution of iron metal
(3) salt solution of zinc metal
(4) salt solution of aluminium metal

Answer 1

Aluminium is more reactive than all the metals given in the options. So, aluminium will displace metals from their respective salts.
From the given options we have salt of iron which is of greenish colour, when aluminium metal placed in iron salt solution colour of solution fades and aluminium piece gets grey coating.
$3{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+2\mathrm{Al}\left(\mathrm{s}\right)\to {\mathrm{Al}}_2\left({\mathrm{SO}}_4{)}_3\right(\mathrm{aq})+3\mathrm{Fe}(\mathrm{s})$

Hence, the correct answer is option 2.