A hydrate is a crystalline ionic compound containing water in its structure. When a hydrate is heated, it gives off a definite amount of water, losing its crystalline form. This definite amount of water is called water of crystallization. If we know the percent composition of the water of crystallization, we can determine the empirical formula of the hydrate.
The empirical formula of a hydrate is the simplest whole-number ratio of water molecules to the anhydrous compound. To determine the empirical formula of hydrate, we must know either the amount of water in it or the amount of the anhydrous salt, which means, the ionic part of the hydrate without water. Generally, these amounts can be reported in grams or percent.
For instance, if the amount of water in the hydrate is 60.00%, we will subtract 60.00% from 100% to get the amount of the anhydrous salt and vice versa. Once we know the amount in percent of salt and water, next we convert the amount in percent to amount in grams, and then calculate the amount in moles for each by dividing the amount in grams by their molar mass.
After getting the moles, we again divide the moles of water of crystallization by the moles of the anhydrous salt to arrive at the empirical formula or water of crystallization of the hydrate. Watch the above video to see how we applied the above steps to solve the following problem
In an experiment you heated a specific amount of the hydrate – CuSO4.XH2O and found that it contains 36.08% of water. Determine the empirical formula of the hydrate