Question

In which one of the hydrated crystals, water molecules present in the interstitial spaces?

• A. ${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$
• B. $\left[\mathrm{Cu}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NH}}_3\right)}_2\right]{\mathrm{Cl}}_2$
• C. ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$
• D. $[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_5{]}^{3+}.3{\mathrm{Cl}}^{-}$

Answer 1

The correct option is A

${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$

Explanation for the correct option:

Option(A): ${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$

• Interstitial water is defined as the water molecules that are present in the interstitial sites of a crystal lattice.
• The Interstitial water molecules are found in the case of ${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$ salt.
• There are two interstitial water molecules present in barium chloride dihydrate
• Between the first and second solvation shells, water molecules are primarily trapped, which can be found in the crystal lattice’s interstitial locations.

Explanation for the incorrect option:

Option(B): $\left[\mathrm{Cu}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NH}}_3\right)}_2\right]{\mathrm{Cl}}_2$

• The water molecule present in this complex is present in its coordinate site, but not in the interstitial site.
• Hence the given Option is the incorrect one.

Option(C):${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$

• In the case of the given complex, the water molecules are present in its coordinate site.
• Thus, the given Option does not satisfy the correct concept.

Option(D):$[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_5{]}^{3+}.3{\mathrm{Cl}}^{-}$

• The water molecules present in this complex are not present in its interstitial site but instead present on the coordinate site.
• Hence the given Option does not coincide with the correct concept.

Hence, among the hydrated crystals, water molecules are present in the interstitial spaces in option (A) ${\mathrm{BaCl}}_2.2{\mathrm{H}}_2\mathrm{O}$ salt.