Magnesium sulfate is also a hydrate and has the formula: MgSO4 . X H20. Of a 3.38 gram sample of the PURE hydrate, only 1.65 grams remained after heating in a crucible. What is the formula of the hydrate?

Question

aaronq · Answer

so you had a total mass of the hydrate (MgSO4 . X H20) of 3.38 g
then you heated it (removed all the water) and had left (MgSO4) 1.65 g
what is the mass that evaporated?  3.38 g-1.65 g= mass of water

convert both of the values, MgSO4 1.65 g and the mass of the water, to moles and see in what proportion they are in