Question

Which of the following salts contain interstitial water molecules in it?

• A. [Cr(H\(_2\)O)\(_6\)]\(^{3+}\), 3Cl\(^-\)
• B. CuSO\(_4\).5H\(_2\)O
• C. [Cu(H\(_2\)O)\(_2\)(NH\(_3\))\(_5\)]Cl\(_2\)
• D. BaCl\(_2\).2H\(_2\)O

Hint:

Salts like BaCl\(_2\).2H\(_2\)O contain interstitial water molecules, which are not part of the coordination sphere but are incorporated in the crystalline structure.

Answer 1

The Correct Option is D

Step 1: Understanding interstitial water.
Interstitial water is the water that is bound loosely between ions in a crystalline structure, often seen in salts like copper sulfate pentahydrate (CuSO\(_4\).5H\(_2\)O) and barium chloride dihydrate (BaCl\(_2\).2H\(_2\)O).

Step 2: Analyzing the options.
(A) [Cr(H\(_2\)O)\(_6\)]\(^{3+}\), 3Cl\(^-\): This is an example of a coordination complex where water molecules are coordinated to the metal ion, not interstitial.
(B) CuSO\(_4\).5H\(_2\)O: This is a hydrated salt with water molecules that are part of the crystal lattice, but not interstitial water.
(C) [Cu(H\(_2\)O)\(_2\)(NH\(_3\))\(_5\)]Cl\(_2\): This is another coordination complex, where water molecules are part of the coordination sphere, not interstitial.
(D) BaCl\(_2\).2H\(_2\)O: This is the correct answer, as it is a salt that contains interstitial water molecules.

Step 3: Conclusion.
The correct answer is (D) BaCl\(_2\).2H\(_2\)O.