Epsom salt is commonly purchased in the pharmacy for a variety of uses, anti-inflammatory, laxative, and cosmetic. epsom salt is a hydrated salt of magnesium sulfate. if 2.000 g of epsom salt are heated to remove the waters of hydration, 0.977 g of the anhydrous (without water) magnesium sulfate, mgso4, were obtained. calculate the number of waters of hydration, and write the chemical formula of the epsom salt.

Epsom salt is MgSO4.
We assume x water of hydration in the crystalline form.

Molecular mass of MgSO4 = 24+32+4*16=120
Molecular mass of MgSO4.xH2O = 120+18x

By proportion, 
2.000/0.977 = (120+18x)/120
Cross multiply
0.977(120+18x) = 120*2.000
from which we solve for x
17.586x+117.24 = 240
x=122.78/17.586
=6.980

there are 7 water of hydration in Epsom salt, according to the experiment.

Note: more accurate (proper) results may be obtained by using exact values (3-4 significant figures) in the molecular masses.  However, since water of hydration is the nearest integer, using approximate values (to at least two significant figures) suffice.