Percent Composition of Hydrates Lab

Purpose:   to measure the percent of water in a series of crystalline compounds called hydrates.

Procedure: 

1. Label each tube with and measure/record the masses

2. Add corresponding compound (2-3g) measure and record mass of each tube and compound

3. Heat contents of test tube and note any changes in appearance of the solid contents

4. Continue heating until moisture is driven from the tube. Heat for 2-3 minutes. Repeat for the other test tubes

5. Allow each test tube to cool, then measure and the mass of each test tube and the heated compound.

Data: 

Tube 1: Calcium dihydrate-
1. Before heat: 2.5 g After heat: 7.45 - 7.39= 0.06 g
2. Difference: 2.44g
3. % water loss: .06/2.5x100= 2%

Tube 2: Sodium sulfate decahydrate-
1. Before heat: 2.6 g After heat: 7.93 - 7.39= .54g
2. Difference: 2.6-0.54= 2.06g
3. % water lost: 0.54/2.6x100= 21%

Tube 3: Copper II sulfate pentahydrate-
1. Before heat: 3.1 g After heat: 7.5 g
2. Difference: 3.1-0.11= 2.99g
3. % water loss: .11/3.1x100= 4%

Observations

Tube 1: no change 

Tube 2: quickly melting, fizzing, changing to liquid, bubbling up, separates when taken off flame 

Tube 3: turning white, flame turns green, turning grey because it is burning, has a burnt smell

4. Sodium sulfate decahydrate lost the

Check:

H2O lost:

Tube 1: 2g(1 mol/18g)= .112 mol 

Tube 2: 21g(1 mol/18g)= 1.167 mol

Tube 3: 4g(1 mol/18g)= .222 mol

Compounds: 

Tube 1: 98g(1mol/110g) = .89 mol

Tube 2: 79g(1mol/142g) = .56 mol

Tube 3: 96g(1mol/250g) = .38 mol

CuSO45H2O

Na2SO410H2O

Na2CO32H2O