The primary and secondary valencies of cobalt respectively in $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{5}\mathrm{Cl}\right]\mathrm{Cl}_{2}$ are :

JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Coordination Compounds

The primary and secondary valencies of cobalt respectively in

[Co (NH_{3})_{5} Cl] Cl_{2}

are :

(A)3 and 5
(B)2 and 6
(C)2 and 8
(D)3 and 6✓ Correct

Answer: (D)

Solution

[Co (N H_{3})_{5} Cl] C l_{2}

the complex ion

[Co (N H_{3})_{5} Cl]^{2 +}

has cobalt bonded to five ammonia molecules and one chloride, so its coordination number, the secondary valency, is six. Cobalt is in the

+ 3

state, balanced by three chlorides in all—one inside the sphere and two outside—so the primary valency is three. The primary and secondary valencies are three and six respectively.

JEE Main · 2023 · 24 Jan 2023 · Shift 1 · Single correct option

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