Given the molecular of the hexacoordinated complexes is `:`
`(1)CoCl_(3).6NH_(3)" "(2)CoCl_(3).5NH_(3)" "(3)CoCl_(3).4NH_(3)`
If the number of co-ordinated `NH_(3)` molecules in `(1),(2)` and `(3)` respectively are `(6),(5)` and `(4)` , the primary valency in `(1),(2)` and `(3)` are `:`

Options

A. `6,5,4`
B. `3,2,1`
C. `0,1,2`
D. `3,3,3`

Answer

4

Explanation

The primary valency is ionisable valency. It corresponds to oxidation state of metal. The primary valency is always satisfied by negatively charged ion i.e. anion.
`underset((1))([Co(III)(NH_(3))_(5)]Cl_(3))rarr[Co(III)(NH_(3))_(6)]^(3+)+3Cl^(-)`
`:. " "`number of primary valency is 3.
`underset((2))([Co(III)(NH_(3))_(5)Cl]Cl_(2))rarr [Cl(III)(NH_(3))_(2)+2Cl^(-)`
`:. " "` number of primary alency is 3.
`underset((3))([Co(IIII)(NH_(3))_(4)Cl_(2)]Cl)rarr[Co(III)(NH_(3))_(4)Cl_(2)]^(+)+Cl^(-)`
`:. " "` number of primary valency is 3.