Laboratory Preparation & Procedure

Materials:

• Deionized water
• 50-mL beaker
• 10-mL volumetric pipette
• Unknown liquid

Safety

Glassware will be used in lab. Be aware of your surrounding and when transferring liquids to avoid broken glass. An unknown liquid will be used that is subject to irritation. Wear googles and gloves at all times and avoid touching or smelling the substance directly.

Procedure:

1. Dry & clean a 50-mL beaker.
2. Record the mass of a 50-mL beaker using the analytical balance under trial 1 in data table 1.
3. Pipette 5-mL of water into the beaker. Record the volume to the correct precision of the pipette.
4. Record the mass of the beaker plus water and determine the mass of the water present.
5. Calculate the density of water and record in data table 1.
6. Repeat steps 1 – 4 for trial 2.
7. Determine the average density of water based on your two trials. Record your average density on the board for use in the class data set.
8. Given the known density of water is 0.998 g/mL at 20°C, calculate the percentage error of the known density of water and your experimental value. Record all values in data table 1.
9. Calculate the average density & standard deviation of the class data set. Record all values in data table 1.
10. Dry & clean a 50-mL beaker.
11. Record the mass of a 50-mL beaker using the analytical balance under trial 1 in data table 2.
12. Pipette 5-mL of the unknown liquid into the beaker. Record the volume to the correct precision of the pipette.
13. Record the mass of the beaker plus unknown liquid and determine the mass of the unknown liquid present.
14. Calculate the density of the unknown liquid and record it in data table 2. Be sure to record the identifier for your unknown liquid.
15. Repeat steps 10 – 13 for trial 2.
16. Determine the average density of the unknown liquid based on your two trials. Record your average density in data table 2.
17. Identify your unknown liquid based on your experimental density using the densities of common organic liquids table below.

Densities of Common Organic Liquids