Question

A student is given a sample of a calcium sulfate hydrate. He places the sample in a dry, covered crucible and weighs it. The total mass (crucible, cover, and hydrate) is 19.39219.392 g. The crucible and cover together had previously weighed 17.98717.987 g. He then heats the crucible to redness for 10 minutes with the cover slightly ajar. After the crucible cools, he weighs the crucible and its contents; the mass is now 19.09819.098 g, due to the loss of water of hydration.

1) What was the mass of the original sample?

mass of the original sample =

g

2) What is the mass of the anhydrous residue, (i.e., the compound minus the water of hydration)?

mass of the anhydrous residue = ?g

3) What was the mass of the water that was driven off?

mass of the water = ?g

4) Calculate the percentage of water in the hydrate.

percentage of water in the hydrate =? %

5) How many grams of water would there be in 100.0 g of hydrate? How many moles?

mass of water in 100.0 g of hydrate = ?g

moles of water in 100.0 g of hydrate = ?mol

6) How many grams of CaSO4CaSO4 are there in 100.0 g of hydrate? How many moles?

mass of CaSO4CaSO4 in 100.0 g of hydrate = ?g

moles of CaSO4CaSO4 in 100.0 g of hydrate = ?mol

7) Calculate the whole number ratio of moles of water to moles of CaSO4.CaSO4.

number of moles of water =

number of moles of CaSO4=CaSO4=

8) Based on the answer to #7, determine the formula of the calcium sulfate hydrate (i.e., CaSO4⋅?H2O).CaSO4⋅xH2O).

?=