Question

It is well known that copper sulfate, sodium sulfate, et al crystallize with 5,10 water molecules of hydration, locked in their crystal lattices. Is it possible to have other molecules instead of water, such as maybe ammonia or hydrogen sulfide?

Answer 1

Other molecules like ammonia can indeed replace water to form different types of hydrates or solvates, such as the deep blue-violet complex ion [Cu(NH3)4]2+, demonstrating that a variety of molecules can coordinate with metal ions in solids.

Step-by-step explanation:

It is indeed possible for other molecules, such as ammonia or hydrogen sulfide, to become incorporated into the crystal lattice in place of water molecules, forming different types of hydrates or solvates. This can happen when these molecules are present in significant concentrations and have suitable properties for coordination, often leading to the formation of complex ions.

For example, the addition of aquous ammonia to a solution of copper sulfate results in the substitution of water molecules by ammonia in the hydrated copper ion, generating a deep blue-violet complex, usually written as [Cu(NH3)4(H2O)2]2+, or more simply as [Cu(NH3)4]2+.

This illustrates the principle that water is not the only molecule that can coordinate with metal ions in solids; a wide range of other molecules with lone pairs of electrons are also capable of fulfilling this role.