Experimental Overview
- You will perform the combustion of benzoic acid twice to calibrate the bomb. (Apparatus Calibration)
- You will determine the heat of combustion of naphthalene. Do an absolute minimum of two runs.
- You will use calorimetry to study a series of compounds with decreasing aromaticity.
Before doing any of the steps above, read the general procedure for performing a bomb combustion run.
Some recommendations for working efficiently :
- Delegate tasks. Have one person weigh samples and wire while the other makes pellets. Once a pellet has been made, the first person can continue weighing while the other gets the apparatus ready for a run.
- You always need to have 2 or 3 runs of any sample in order to get an estimate of your errors. However, you should do one run of each compound before you start repeating. (For examples, if you are doing the aromatic series experiments, combust benzoic acid, naphthalene, #1 of the aromatic series, #2 of the aromatic series, #3 of the aromatic series.) After one measurement of each compound has been done, then begin repeating measurements. That way, if you run out of time, you will have at least one measurement for each.
Other hints:
The sample that you combust in the bomb is ignited with a small piece of iron wire which also burns and add to the overall heat of combustion of the system. This iron wire may not always fully combust in the bomb. You must carefully weigh the iron before AND AFTER the combustion in order to find out how much iron wire was combusted.
Normally, there is some nitrogen present in the atmosphere of the bomb. This would result in the formation of nitric acid and would offset the total heat of reaction. You MUST flush the bomb at least three times with pure oxygen to eliminate any contribution from the nitrogen reaction.
Combustion of an Aromatic Series
