How much Energy is Released from the Combustion of Various Alcohols

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Chemistry coursework                        DeveshPAREKH

How much Energy is Released from the Combustion of Various Alcohols


To investigate how much heat energy is released when various alcohols (methanol, ethanol, propan-1-ol, butan-1-ol, and pentan-1-ol) combust.


Scientific Background of Alcohols

Methanol, ethanol, propan-1-ol and butan-1-ol are part of the alcohol homologous compound series, which is defined by their function group of –OH. Below is the structure of ethanol:

The general formula for alcohols is CnH2nn+1OH. As I have proved earlier on in my prediction, larger alcohol chains have release more energy when combusted because they have more bonds, but this also means they have a higher boiling point:

Ethanol burns with the following equation:

Ethanol + oxygen  carbon dioxide + water

2CH3OH + 3O2  2CO2 + 4H2O

This means that the burning of an alcohol (in this case ethanol) releases only carbon dioxide and water, which are environmentally friendly products so alcohols as fuels are environmentally friendly.

The production of alcohol is also easy. It can be fermented:

Glucose  ethanol + carbon dioxide

Which is environmentally friendly or through the hydration of ethene:

C2H4(g) + H2O(g)                 C2H5OH(g)


I believe that larger chains of alcohol (e.g. propan-1-ol) will combust to release more heat per a mol than a shorter chain of alcohol s(e.g. ethanol).

Scientific basis

I believe this because using bond energies we can find out the energy stored in 1 mol or reactant and see how much energy is lost (endothermic reaction) in the formation of 1 mol of product. Below is the various types of bonds involved in the reactants in the combustion of methanol:


Reactant                Product

From this we can now tell that the total amount of energy released from burning a mol of methanol is only (5606-5144/2=) 231J.

If we now do the same for the burning of propan-1-ol, we should see a raise in the amount of energy being emitted:


Reactant                                           Product

Here we can see that the amount of energy released from burning propan-1-ol is (13270-11728/2=) 771J. This is a lot more than the energy released from the burning of 1 mol of methanol (by 540J) and this shows that a longer chain of carbons in an alcohol releases more energy per a mol of the substance burned.

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A preliminary experiment was done to get practise at doing the method and to find out what was wrong with the method. A candle was weighed and then burned under a Coke™ can filled with 300cm2 of water. Once the temperature of the water had risen by 20oC, the candle was weighed again. The experiment was done twice to get more accurate results. The difference in the initial mass and final mass was the amount of candle burned in the experiment and this was recorded to be an average of 1.06 grams. The preliminary experiment brought ...

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