Experiment 7
| The Heat of Combustion of Vegetable Oil |  |
Procedure and Results
Stockroom: Things for each group to borrow and return on the same day.
 | Juice can |
| 2 - 30 ml beakers |
| 2 wicks (do not return) |
Procedure
| Using
two pieces of copper wire, form two wick holders to fit
in 30 ml beakers as shown in the diagram. The holder
should extend across the diameter of the beaker about 1/3
of the way from the top. Fit the wick-holders and wicks
in each beaker. The wick should extend from the bottom to
slightly above the top of each beaker. When the wicks are
in place, fill one beaker to within 1.5 cm of the top
with 1-dodecanol, taking care to avoid getting it on the
outside surface of the beaker. Fill the other one in the
same way with vegetable oil. Light both burners to be sure they work properly. If either burner has an excessively sooty flame, you will need to use scissors to trim the wick. Blow out the lamps and allow them to cool. Trim the wicks if necessary. |
|
Clamp a 250-ml Erlenmeyer flask to a ring stand, place one of the burners under it, and adjust the height of the flask so that the bottom of the flask is about 1. cm above the top of the burner wick. Remove the flask from the clamp, but do not change the height of the clamp on the ring stand. This height must remain constant throughout the experiment. Insert the neck of the flask through the hole in the bottom of the coffee can, and re-clamp the flask to the ring stand. Your apparatus should look like the one in the figure shown below.
Calibration of the Calorimeter
Determine the mass of the dodecanol burner by weighing it on a balance. Be careful not to spill any of the oil because you must determine the mass of the oil burned in the combustion reaction. Record the mass.
Using a graduated cylinder, transfer exactly 200 ml of tap water to the Erlenmeyer flask. Stir the water thoroughly with the thermometer, read the temperature to the nearest 0.2 C° and record it in your notebook.
Quickly re-light the dodecanol burner and place it under the flask centering the flame under the bottom of the flask. The easiest way to do this is to tip the ring stand back so that the burner can be slipped under the coffee can, and then lower the ring stand to its original position. Stir the water with the thermometer (be careful, it is fragile), and when the temperature of the water in the flask has risen about 10 C° -- 12 C°, blow out the flame. Continue to stir the water, recording the highest temperature reached. Remove the burner and when it has cooled to room temperature, re-weigh it and record the mass. While the lamp is cooling, empty the water from the flask, clean the soot off the bottom, and refill the flask with 200 ml of tap water as before. Repeat this calibration.
Heat of Combustion of the Vegetable Oil
Record the type of vegetable oil you use. Weigh and record the mass of your vegetable oil burner. Determine the heat given off by the combustion of the vegetable oil twice, using the same procedure used to calibrate the calorimeter, except that the dodecanol burner should be replaced by the vegetable oil burner.
The dodecanol and vegetable oil can be put down the drain. Wash the beaker with soapy water; return the equipment to the Stockroom.
Results
Use the table below as a guide for organizing your calculations. All data and calculations should be in the "Results" section of your report.
Calibration by Combustion of 1-Dodecanol
| Data | Trial 1 | Trial 2 |
| initial mass of burner (g) | ||
| final mass of burner (g) | ||
| initial temperature of water (C°) | ||
| final temperature of water (C°) |
| Calculations | Trial 1 | Trial 2 |
| mass of 1-dodecanol burned (g) | ||
| temperature
change of the water (C°) (final temperature-initial temperature) |
||
| heat
of combustion of dodecanol (cal) (mass x 10102 cal/g) |
||
| calibration
value (cal/C°) (heat of combustion / temperature change) |
||
| average calibration value (cal/C°) | ||
Heat of Combustion of Vegetable Oil
| Data | Trial 1 | Trial 2 |
| initial mass of burner (g) | ||
| final mass of burner (g) | ||
| initial temperature of water (C°) | ||
| final temperature of water (C°) |
| Calculations | Trial 1 | Trial 2 |
| mass of vegetable oil burned (g) | ||
| temperature
change of the water (C°) (final temperature-initial temperature) |
||
| actual
heat of combustion of vegetable oil (cal) (calibration value x temperature change) |
||
| heat
of combustion per gram of oil burned (actual heat of combustion / mass of oil burned) |
||
| average heat of combustion per gram of vegetable oil | ||