Question

In ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$ what are their secondary valency and the number of hydrogen bonds?

• A. $6\mathrm{and}4$
• B. $4\mathrm{and}1$
• C. $5\mathrm{and}1$
• D. $6\mathrm{and}5$

Answer 1

The correct option is B

$4\mathrm{and}1$

The explanation for the correct options:

B. $4\mathrm{and}1$

The secondary valency:

• In the diagram the ${\mathrm{CuSO}}_4$ is coordinated with four water molecules.
• So the secondary valency is $4$.
• Its geometry is square planar.

The number of hydrogen atoms:

• In ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$ is coordinated with $4$ water molecules and two more oxygen atoms from sulphate ions.
• The fifth water molecule is highly embedded so it cannot be coordinated.
• So 4 molecules are only coordinated and only one is hydrogen-bonded.

Hence, option (B) is the correct answer.