Final answer:
The name of the hydrate MgSO4·7H2O is Epsom salts. When heated, water is evaporated from the hydrate, and the mass decreases. The number of water molecules can be calculated by the change in mass and is consistent with seven molecules of water in the hydrate, confirming the compound as MgSO4·7H2O.
Step-by-step explanation:
The hydrate MgSO4·7H2O is commonly known as Epsom salts. This compound is a type of hydrate where the magnesium sulfate is bonded to seven molecules of water. When you heat magnesium sulfate hydrate, the water molecules are lost, and the mass of the compound decreases. To determine the number of water molecules in the original sample, we subtract the final mass from the initial mass. This difference (5.0 g - 2.6 g) is 2.4 g, which represents the mass of the water that was in the original hydrate sample.
Given that the molar mass of water (H2O) is approximately 18 g/mol, we can calculate the number of moles of water that were lost during heating. If we divide the mass of the evaporated water by the molar mass of water (2.4 g ÷ 18 g/mol), we get approximately 0.133 moles of water. Since there are 7 moles of water for each mole of magnesium sulfate in Epsom salts, this calculation suggests that the original hydrate was indeed MgSO4·7H2O.