Question

Based on your results, was this setup a good way to measure Calories as opposed to a bomb calorimeter? What types of experimental error may have occurred with this experiment? How might you design this setup differently if you had unlimited expenses for materials?

Answer 1

Yes, A bomb calorimeter is only approximately adiabatic.  In reality, there is a small heat leak through the dewar and the stirrer does work on the calorimeter.  Nonadiabaticity is corrected for with an empirical radiative correction, RC.

The time at which the bomb is considered to be fired is the time that makes the areas indicated in the above figure equal.  For the Parr calorimeter, this is estimated to be at t = 7 minutes.  Thus, the temperature at t = 6 minutes must be extrapolated forward 1 minute by the pre-firing slope, and the temperature at t = 12 minutes must be extrapolated backward 5 minutes by the post-firing slope.  

Mathematically, this is done as follows

The possible sources of experimental errors would be:
1)error in measuring the mass of sample.
2)error in measuring the temperature increase of the calorimeter.
3)error calibrating the measuring instruments.

Corrections in Bomb Calorimetry:.  Combustion of fuse

Nickel and iron fuses can burn according to

Ni + O₂ NiO

or

2Fe + O₂ Fe₂O₃

The heat released by combustion of the fuse is accounted for by recognizing that

DU = DUsample·msample + DUburned fuse·mburned fuse = -Cv DT

where the mass of the burned fuse is determined by weighing the fuse before and after firing the bomb.