Experimentally measuring the percentage water in a hydrate involves first heating a recognised mass of the hydrate to take away the waters of hydration and then measuring the mass of the anhydrate remaining.
The distinction between the two loads is the mass of water lost.
Determine the mass of the water that has left the compound. Take the mass of the hydrate and subtract the mass of anhydrate from that to get the mass of water. 210.4 g MgSO4 nH2 O - 120.4 g MgSO4 = 90 g H2 O. Convert the mass of water to moles.
Learn more about mass of water during heating here:
