# Barium chloride crystals contain 14.8% water of crystallization.Find the number of molecules of water of crystallization per molecule.

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Expert Answers

mlsiasebs | Certified Educator

The waters of crystallization tell us the amount of water associated with a particular molecule. Hydrated compounds have a specific number of water molecules associated with it and that number is a characteristic property of a substance. The percentage for the water of crystallization is found by taking the mass of the hydrate molecules and dividing it by the molar mass of the hydrated molecule.
% = 100* mass of water molecules / mass of hydrated salt
We'll use x for the mass of the water, we know the percentage, and we can find the mass of the unhydrated salt, which is 208.3 g/mol
14.8 = 100x / (208.3+x)
Divide by 100 to get
0.148 = x / (208.3+x)
Rearrange to solve for x
0.148(208.3+x) = x
30.8 + 0.148x = x
30.8 = 0.852x
x=36.2
Since we assigned x as the mass of water, we have 36.2 g of water. In order to have a mass of water of 36 g, we need two moles of water so the formula will be BaCl2-2H2O.