Question

Which statement best describes the water molecules in a hydrate?

They slide around the ions throughout the crystal lattice.
They vibrate but are held in fixed positions in the crystal lattice.
They have no motion because they are held in fixed positions in the crystal lattice. They vibrate randomly along the outer edges of the crystal lattice.

Answer 1

Answer: Option (a) is the correct answer.

Step-by-step explanation:

Water is a liquid form of matter and in this molecules are less tightly held together due to less intermolecular forces of attraction between them.

As a result, molecules are able to slide past each other.

Whereas in a solid state, molecules are held through strong intermolecular forces of attraction. As a result, they are held in fixed position and they can vibrate in the crystal lattice.

On the other hand, when a substance is in gaseous state then molecules are held through weak Vander waal forces. As a result, molecules move in rapid random motion.

Therefore, we can conclude that the statement they slide around the ions throughout the crystal lattice, best describes the water molecules in a hydrate.

Answer 2

Which statement best describes the water molecules in a hydrate?

They slide around the ions throughout the crystal lattice.
They vibrate but are held in fixed positions in the crystal lattice.
They have no motion because they are held in fixed positions in the crystal lattice.
They vibrate randomly along the outer edges of the crystal lattice.

The best answer seems to be (1). (2) is invalid because the water does not bond with the ions. (3) violates laws of chemistry, while (4) does not hold true for all substances as sometimes the water of hydration can be "inside" the crystal lattice.