Does any one know what the random errors are in enthalpy of combustion of alcohols experiment? like methanol, ethanol, etc.
Answers
The combustion was not quite complete, i.e. didn't wait long enough (formed soot on the reaction pan).
Thus, the actual yield might be a bit lower than expected.
No water was put inside the bomb calorimeter to saturate its atmosphere, so the force from the combustion may not have condensed all the water vapor back into a liquid (since the calorimeter was sealed, at a constant volume).
To account for this, I found the vapor pressure of water at my lab's temperature and pressure, and used water to measure the bomb's volume. The temperature I used was the temperature of the room.
Then, I used the ideal gas law to calculate the mols of water that was still gaseous, subtracting those mols from the total mols of water (liquid + vapor) formed.
The measurement of what pressure
O
2
you used.
For instance, I had to estimate how many
PSI
I used and simply wrote, "a bit less than
450 PSI
" in my report.
Technical error, such as the calorimeter failing to run (usually not an issue you need to report, since it doesn't affect the results you'd have when you redo it)