calcium sulfate is known to form hydrates (ionic compounds with water that have well-defined ratios of the ionic formula unit to molecules of water, written caso4⋅nh2o). the water content of the hydrate can be determined by gravimetric analysis. how many molecules of water are present for every formula unit of caso4 in an unknown calcium sulfate hydrate if a complete drying of a sample to anhydrous caso4 caused its mass to decrease from 8.609g to 6.807g?