Question

Question #966b5

Answer 1

See below.

Explanation:

Test for `Cr^(3+)` is treating it with NaOH. It gives a grey-green precipitate which is soluble in excess NaOH to give a dark green solution.

Or you can treat it with aqueous `NH_3` where it forms a grey-green precipitate and insoluble in excess ammonia.

It dissolves in dilute HCl to form solutions containing `Cr^(2+)`. So it would be 3.