November 5, 2010: Hydrate Lab (Angelo)

Hydrate Lab:

Discussion:
Hydrates are ionic compounds that contain an inorganic salt compound loosely bound to water. The purpose of this experiment is to determine the empirical formula of a hydrate. Examples are: magnesium sulfate heptahydrate (epsom salts) and sodium carbonate decahydrate (washing soda). The formulas for substances are MgSO4*7H2O and Na2Co3*10H2O. They can also be represented as MgSO4(H2O)7 and Na2CO3(H2O)10. In this lab you will be dtermining the anhydrous (without water) mass of the hydrate. You will compare this with the actual mass of water that should be present.

Materials:
- Bunsen burner
- Test tube
- Test tube rack
- Test tube clamp
- Weight scale
- Cobaltous chloride hexahydrate

Procedure:
1. Fill a test tube about 1 cm. with the hydrate.
2. Carefully place the test tube on the scale and record the mass of the hydrate and test tube.
3. Using extreme caution, connect andl ight your Bunsen burner. Adjust the gas flow until the flame is about five cm. tall.
4. Pick up the test tube with the clamps and carefully hold it in above the Bunsen burner.
5. Gently heat the test tube by moving the test tube in and out of the flame for about 5 minutes or until all the water has boiled away.
6. Carefully re-weight the test tube ensuring none of the chemicals inside spill.

Observation:
Test Tube Weight - 18.78 grams
Mass Before Heating - 19.38 grams
Mass After Heating - 19.09 grams

Analysis:
1. Determine how much water was released during the heating? 0.29 grams
2. What percent of the hydrate was water? 48%

Conclusion:
1. The actual percent water in this hydrate is 45%. Determine your percent error for part 2.
Write out the formula: [(measured - accepted) / (accepted)] x 100 
Plug in the numbers: [(48% - 45%) / (45%)] x 100
Calculate: 6.7%

In this lab conducted, the percent error was 6.7 percent.