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

To solve the problem, we will break it down into three parts as specified in the question.

### Part (i): Write the formulae of isomers A and B.

1. **Identify the ligands and their positions**: The complex is `Cr(NH3)4Cl2Br`. The two isomers A and B differ in the arrangement of the ligands.

2. **Determine isomer A**: Since isomer A reacts with AgNO3 to form a white precipitate, this indicates that chloride (Cl-) is the ion that is being released. Therefore, in isomer A, the chloride must be outside the coordination sphere. The formula for isomer A is:
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