A complex compound of `Cu^(3+)` with molecular formula `CoCl_(x).yH_(2)O` gives a total of 3 ions on dissolving in water. To satisy both the primary and secondary valencies in the complex , the number of `Cl^(-)` ions required is :

Explanation

Since, the complex gives total of 3 ions on dissolving in water, cobalt is in `+3` oxidation state `Co^(3+)` and the co-ordination number of cobalt is 6.
The molecular formula of the complex = `CoCl_(3).YNH_(3)`.
Since the complex gives a total of three ions on dissolving in water, its structrual formular = `[CoCl(NH_(3))_(5)]Cl_(2)`.
The complex dissociates in aqueous solution as : `+2Cl^(-)[CoCl(NH_(3))_(5)]Cl_(2) ltimplies [CoCl(NH_(3))_(5)]^(2+)`
Thus, one `Cl^(-)` ion satisfies both the primary and secondary valencies of the metal while the remaining two (ionisable) satisfy the secondary valencies.