Lab 5B: Composition of a Copper Sulfate Hydrate Lab

We took a sample of carbon sulfate hydrate and tried to find the ratio of carbon sulfate and H2O.
We heated up the sample in an evaporation dish to find out how much water was in the sample and calculated the ratio.

Copper Sulfate Hydrate

Heating up the Copper Sulfate Hydrate

All the water has evaporated from the compound to create Copper Sulfate

1. Calculate the mass of the hydrate.

(Mass of evaporating dish and hydrate) - (mass of evaporating dish) = Mass of hydrate

45.88 - 44.97 = .91 grams of copper sulfate hydrate



2. Calculate mass of the water lost.

(Mass of evaporating dish and hydrate) - (Average of Mass of dish and hydrate after heating 2 times) = Mass of Anhydrous salt

(45.22+45.68)/2 = 45.45 = Average of Mass of the dish and hydrate after heating it twice

45.88 - 45.45 = .43 grams of water


3. Calculate percentage of water in the hydrate.

(Mass of Water)/(Mass of total hydrate)= percentage of water in the hydrate

(.43)/(.91) x 100 = 47% water 


4. Calculate percent error.

Actual percent is 36%               (|Experimental Value - Actual Value| / Acutal value) x 100 = % error

(|.47-.36| / .36) x 100 = 30.5 % error


5. a) moles of water evaporated

1 mole of H20 = 18.0148 grams
conversion:
(.43 g H2O/1) x (1 mol/18.0148 g H20) = .0238 moles of H20

b) Moles of CuSO4 that remain in evaporating dish:

1 mole of CuSO4 = 159.61 grams
conversion:
(.48 g CuSO4/1) x (1 mol/ 159.61 g CuSO4) = .003 moles

c) Find the ratio of moles of CuSO4 to moles of H2O.

.003/.003 = 1
.0238/.003 = 7.9 or 8
1 to 8

d) What is the empirical formula of the hydrate.

(CuSO4)1 (H20)8


However, because our percent error was fairly high, we predict a different result. Our percent of water lost is greater than the actual answer so the real coefficient for water should be smaller than eight.