Epsom salts are hydrates of magnesium sulfate. the formula for epsom salt is mgso4·7h2o. if a 7.834 g sample is heated until constant mass is obtained, what is the mass of the anhydrous magnesium sulfate? what percent of the hydrate is water?

1. For the first question, we must find the mass of the anhydrous salt, MgSO₄. The molar mass for MgSO₄·7H₂O is 246.47 g/mol, while that of MgSO₄ is 120.37 g/mol.

7.834 g MgSO₄·7H₂O * 1 mol MgSO₄·7H₂O/246.47 g * 1 mol MgSO₄/1 mol MgSO₄·7H₂O * 20.37 g MgSO₄/mol = 0.647 g MgSO₄

2. Mass of Water = Mass of sample - Mass of anhydrous sale

Mass of water = 7.834 - 0.647 = 7.19 g

Percent Water in Hydrate = 7.19/7.834 * 100 = 91.74%