The secondary valency and the number of hydrogen bonded water molecule(s) in $\mathrm{CuSO}_{4} .5 \mathrm{H}_{2} \mathrm{O}$ respectively, are:

JEE Main · 2021 · 18 Mar 2021 · Shift 2 · Coordination Compounds

The secondary valency and the number of hydrogen bonded water molecule(s) in

CuSO_{4} .5 H_{2} O

respectively, are:

(A)6 and 4
(B)4 and 1✓ Correct
(C)5 and 1
(D)6 and 5

Answer: (B)

Solution

In the crystal four of the five water molecules occupy the coordination sphere of copper(II), giving the square planar

[Cu (H_{2} O)_{4}]^{2 +}

unit, so the secondary valency, which is the coordination number, is

4

. The fifth water molecule lies outside that sphere and is held in place by hydrogen bonds, two to coordinated water molecules and two to oxygen atoms of the sulphate ion, so exactly one water molecule in the formula unit is hydrogen bonded. The secondary valency is

4

and the number of hydrogen bonded water molecules is

1

JEE Main · 2021 · 18 Mar 2021 · Shift 2 · Single correct option

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