I just finished a lab and I was wondering if anyone could point out where I'm going wrong.(adsbygoogle = window.adsbygoogle || []).push({});

Here are my findings for CaSO4:

After First Heating After Second heating

Wt. of crucible, lid, and hydrate 35.0537g 34.9779g

Wt. of dry crucible and lid 34.0226g 34.0226g

Wt. of hydrate 1.0331g 0.9553g

Wt. of crucible, lid, and anhydrate 34.9779g 34.9781g

Wt. of crucible and lid 34.0226g 34.0226g

Wt. of anhydrate 0.9553g 0.9555g

Questions:

1. Calculate the % by weight of water in your unknown hydrate. Report the % to four digits.

1.0331g CaSO4*H2O - 0.9555g CaSO4 = 0.0756 g H2O

0.0756g/1.0311g x 100% = 7.332%

2. Using the % water from Part 1 above, calculate the moles of water. (Hint: Assume a 100g sample of hydrate.) Report to four digits.

7.332g H2O x 1mol. H20/18.02 g H2O = 0.6806 mol H2O

3. Using the & anhydrate, calculate the moles of anhydrate. Report four digits.

100% - 7.332% = 92.668%

92.668g CaSO4 x 1 mol CaSO4/136.15g CaSO4 = 0.6806 mol CaSO4

4. Using the anhydrate formula (CaSO4) given to you in lab, and the values from Parts 2 and 3 above, give the formula of your unknown hydrate. Show your calculation. Round the water to the nearest 1/2 or whole number of moles.

H2O = 0.4069 mol/0.4609 mol =1

CaSO4 = 0.6806 mol/0.4609 mol = 1.673

x 3 = 5CaSO4*3H2O

These calculations don't seem to be right, can anybody please help me understand?

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# Homework Help: Hydrated calcium sulfate - problem determining mass of H2O

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