Hi everyone,
I'm doing my U4 AOS3 (prac) SAC on fuels, as my school has not assessed most of U3 AOS1. The prac focuses on producing a biodiesel from vegetable oil, then determining and comparing the density and energy content on each fuel.
Because of lockdown, we weren't able to complete the experiment ourselves, so the teachers provided the following sample data (to analyse as practice):
For the energy content determination (combusting fuels with a spirit burner to heat water, recording \(\Delta T\) of water):
- \(v(H_2O)=50\ mL\)
- \(v(fuel)=10\ mL\)
- \(\Delta m(fuel)=3.66g\) (for both fuels)
- \(\Delta T=+28.5^\circ C, +31.0^\circ C\) (oil and biodiesel respectively)
Using this data, I determined the energy content of the oil and biodiesel each as follows:
These values seem very inaccurate, given that fats/oils typically have a heat of combustion \(\sim 37kJg^{-1}\). Am I forgetting something and doing a step wrong, or is this data just unrealistic? I've checked over the units, given data, and calculations a hundred times but still can't figure out what's wrong. Under the results column, the rubric does specify that 'any outliers should be identified (if appropriate)', but I'm hesitant to declare this a huge systematic error caused by a terribly calibrated thermometer or similar.
Any help would be greatly appreciated.