How is the number of water of crystallization determined?

Answer 1

The number of water molecules in a hydrate can be determined by Thermogravimetric analysis. In a laboratory, it can be done as follows.

1. Take a hydrated salt sample of known mass, m1.
2. Heat it in the presence of a dessicant to dehydrate it, measure the mass again. Let this mass be m2.
3. Subtract m2 from m1. This is the mass of water present in the sample, m.
4. Divide the factor m with molar mass of water i.e. 18.015 g.
5. The factor given thus is the number of water molecules in the sample.

It should be kept in mind that this method is not as accurate as the termogravimetric analysis.

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Answer 2

The number of water molecules in a compound's crystal structure can be determined by techniques such as thermogravimetric analysis (TGA) or X-ray crystallography. TGA measures the weight loss during heating, with the loss in weight corresponding to the removal of water molecules. X-ray crystallography provides a detailed atomic structure of the compound, including the positioning of water molecules within the crystal lattice.