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

(a) Isomer A: `[Cr(NH_(3))_(4)BrCI]CI.`
Isomer B : `[Cr(NH_(3))_(4)CI_(2)]Br.`
(b) Hybridisation of Cr in isomer A and B is `d^(2)sp^(3)`.
(c) Number of unpaired electrons in `Cr^(3+)(3d^(3))` is 3.
Magnetic moment `=sqrt(n(n+2)) = sqrt(3(3+2)) = 2.87 BM`