A metal complex having composition `Cr(NH_(3))_(4)Cl_(2)Br` has been isolated in two forms (P) and (Q). The form (P) reacts with `AgNO_(3)` to give a white precipitate. Readily soluble in dilute aqueous ammonia, whereas (Q) gives a pale yellow precipitate soluble in concentrated ammonia. Write the formula of (P) and (Q) and state the hybridisation of Cr in each. Calculate the magnetic moments (spin only value).

Explanation

Since `Cr` has the coordination number of six, the two forms of the complex `Cr(NH_(3))_(4)Cl_(2)Br` may be represented as follows -
`underset("(P)")([Cr(NH_(3))__(4)ClBr]Cl)" "underset("(Q)")([Cr(NH_(3))_(4)Cl(2)]Br)`
With these formnulae of (P) and (Q). The experimental results can be explained by the following equation

The hybridisation state of `Cr` in both the complexes is `d^(2)sp^(3)`. The electronic configuration of `Cr` in both the complexes is `d^(2)sp^(3)`. The electronic of `Cr` in the complexes (P) and (Q) can be represented as follows -

Magnetic moments of the complexes
`=sqrt(n(n+2))BM=sqrt(3(3+2))BM=3.87BM`