So as you can see by my results Butanol has the highest enthalpy of combustion.?
To calculate the energy produced or lost during these experiments I used the formula:
DH= mass of water x 4.2 x Dt = J/g
DM
This is the formula m x x t where m is the mass of the water and c is the energy needed to heat up 1kg of the substance 1°C.
We then divide this by 1000 to get the answer in kJ/mol but this requires me to multiply the answer by the r.m.m of the different alcohols these are: (R.M.M is the relative molecular mass which is the values of all the atoms added up together)
Methanol = 32
Ethanol = 46
Propanol = 60
Butanol = 74
?
So as you can see by the two graphs of DH against the number of Carbon atoms the two lines are no where near each other this shows the graph is no where near what I predicted.
There is no major trend on these graphs apart from there is an uprising slope this is due to the fact the enthalpy of combustion increased from Methanol to Butanol but there is a slight anomalous result on the green line at propanol it should be higher than Ethanol but in fact it is not.
For every extra Carbon atom in the alcohol, more moles of Carbon dioxide and Water are formed per mole of alcohol and more energy is released per mole of alcohol as the number of Carbon atoms increased.
C=O bond = 743 and C-H bond = 412 this means that more energy is released as bonds formed than the bonds breaking so there is a higher DH
This conclusion actually agrees with my prediction at the start of the experiment however the results do not although there is still a relationship between the number of Carbon atoms and the enthalpy of Combustion so I am 50% right although there is one major anomalous result. To try and get more accurate results I could only use some of the results and discard any of the anomalous ones.
Evaluation
My results show how much energy is released for a certain number of Carbon atoms in an alcohol. Although the results were easy to carry out I did get different results from my predicted ones which I did using the Bond Energy Tables. The accuracy of my results was not 100% but the graph was what I predicted it to look like. I did get one anomalous result for propane as I have circled it on the first above graph to indicate it was anomalous.
The experiment was not carried out in the idealist of conditions and heat was lost in the surrounding atmosphere. This was due to windows being opened and closed causing draughts to distract the heat supply and the people in the room were carrying out movements which also caused convection currents. As I have said my results are not perfect but the graph was the same shape which can help me support my conclusion.
Improvements which could be made is that the experiment could be done in a room where there are little occupants to try and stop draughts and a room that there are no windows or all of them are closed and could not be open for the same reason. More accurate balance could be used to ensure the best possible results. Also we could use the same spirit burner throughout to ensure there are no faults with the rest and that we should get the same results out of them all.