A metal complex having composition `Cr(NH_(3))_(4)CI_(2)Br` has been isolated in two forms A and B. The form A reacts with `AgNO_(3)` to give a white precipitate readily soluble in dilute aqueous ammonia whereas B gives a pale yellow precipitate soluble in concentrated ammonia.
(i) Write the formulae of isomers A and B.
(ii) State the hybridisation of chromium in each of them.
(iii) Calculate the magnetic moment (spin only) of the isomer A.

Explanation

The data suggests that the two complexes are ionisation isomers. In the form A , one `Cl^(-)` ion is present in the ionisation sphere while the from B, one `Br^(+) ` ion is the part of ionisation sphere. The formulae of the two ionisation isomers are :
`[Cr(NH_3)_(4)BrCl]^(+)Cl^(-)` `[Cr(NH_3)_(4)Cl_2]^(+)Br^(-)`.
(A) (B)