Laboratory Preparation & Procedure

Materials:

• Deionized water
• 50-mL beaker
• 100-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.

Procedure:

1. Pour approximately 20-mL of water from the DI water bottle into a 100-mL beaker.
2. Clean & dry a 50-mL beaker.
3. Record the mass of a 50-mL beaker using the analytical balance under trial 1 in data table 1.
4. Using the 10-mL pipette, transfer 5-mL of water from the 100-mL beaker into the previously massed 50-mL beaker. Record the volume of water transferred to the correct precision of the volumetric pipette. (Never pipette directly from the stock bottle.)
5. Record the mass of the beaker plus water in data table 1.
6. Calculate the mass of the water present by determining the difference between the (mass of beaker + water) – (mass of beaker). Show this calculation in data table 1 in the row labeled “calculation” directly underneath the row entitled, “mass of water”.
7. Calculate the experimental density of water and record in data table 1. Show this calculation in the row directly underneath in data table 1. Be sure to report your density to the proper number of significant figures & include units in your answer.
8. Dispose of your water in the waste beaker in the fume hood.
9. Repeat steps 1 – 4 for trial 2. Use a fresh aliquot of water for trial 2.
10. Determine the average density of water based on your two trials. Show this calculation in data table 1. There should be only 1 average density recorded.
11. Given the known density of water is 0.998 g/mL at 20°C, calculate the percent error of the known density of water and your experimental value (average). Show this calculation directly underneath the row entitled “% Error” in data table 1.
12. Report your average density on the board for the class data set.
13. Record all values on the board for Table 2 – Class Data set.
14. Calculate the average density & standard deviation of the class data set. You will use these values to answer questions in the post lab.
15. Gather an unknown liquid from the instructor at the front. Be sure to record the identifier of your unknown liquid.
16. Clean & dry a 50-mL beaker.
17. Record the mass of a 50-mL beaker using the analytical balance under trial 1 in data table 3.
18. Using the 10-mL pipette, transfer 5-mL of the unknown liquid into the beaker. You may pipette the unknown directly from the given test tube. Record the volume transferred to the correct precision of the device.
19. Record the mass of the beaker plus the unknown liquid in data table 3.
20. Calculate the mass of the unknown liquid transferred by determining the difference between the (mass of beaker + unknown liquid) – (mass of beaker). Show this calculation in data table 3 in the row labeled “calculation” directly underneath the row entitled, “mass of unknown liquid”.
21. Calculate the experimental density of the unknown liquid and record it in data table 3. Show this calculation in the row directly underneath in data table 3. Be sure to report your density to the proper number of significant figures & include units in your answer.
22. Dispose of your unknown liquid in the waste beaker located in the fume hood.
23. Repeat steps 15 – 21 for trial 2. Use a fresh aliquot of the same unknown liquid for trial 2.
24. Determine the average density of the unknown liquid based on your two trials. Show this calculation in data table 3. There should be only 1 average density recorded.
25. Identify your unknown liquid based on your experimental density using the densities of common organic liquids table below & record its identity in data table 3.
26. Calculate the percent error between your experimental density & the theoretical density of your unknown liquid. Show this calculation in your data table.

Densities of Common Organic Liquids