Comparing the enthalpy changes of combustion of different alcohols
What are alcohols?
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Alcohol is the common family name for the hydrocarbon group alkanols.
At least one of the hydrogen groups is replaced by an OH group. They are all organic compounds.
The general formulas for the alcohols are:
CnH(2n+1)OH
Where n represents a number.
The first and simplest member of the alkanols family is methanol.
Its molecular formula is CH3OH.
You can now see that each member of the alcohol family has a different number of carbons in its structure. They increase by one carbon atom and two hydrogen atoms each time.
The question that this piece of coursework is going to answer is
“Is there a relationship between the number of carbon atoms in a chain and the enthalpy change of combustion?”
Aim
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The aim of this experiment is to prove that the longer the hydrocarbon chain the higher the amount of energy transferred to the water, therefore fewer moles of fuel will be used to achieve a temperature rise of 15°C.
The enthalpy change of combustion is the amount of energy transferred when one mole of a substance burns completely in oxygen (always ´ve).
To work out the enthalpy change of combustion of the alcohols the energy output must be measured. The easiest way to do this accurately is to use the thermal energy of combustion to raise the temperature of a substance with a known specific heat capacity, (the amount of energy required to increase the temperature of 1g of a liquid by 1°C).We will be using water.
Prediction
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I predict that the longer the hydrocarbon chain the more energy will be transferred to the water, therefore fewer moles of fuel will be used to achieve the same temperature rise.
So as the number of carbon atoms increases the enthalpy of combustion will become more negative.
Alcohols to be used to compare
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- Methanol = CH3OH
- Pentan-1-ol = C5H11OH
- Propan-1-ol = C3H7OH
- Propan-2-ol = C3H7OH
- Butan-1-ol = C4H9OH
- Butan-2-ol = C4H9OH
I have chosen these alcohols because I will have a chain containing 1 carbon atom, 3 carbon atoms, 4 carbon atoms and 5 carbon atoms. I have also decided to use structural isomers of two of these, Propanol and
Butanol. (Propan-1-ol and propan-2-ol and Butan-1-ol and butan-2-ol).
This will allow me to compare the enthalpy of combustion of increasing chain length and the structural isomers of some of these alcohols.
GRAPH
Equipment required.
- Small copper can to act as a calorimeter
William H. Pierson, Jr., American Buildings and Their Architects: Technology and the Picturesque, (Doubleday & Company, Inc.), 167.
+ 360 + (3 348) + 463 = 5575. Pentan-1-ol has eleven C-H bonds, 4 C-C bonds, 1 C-O bond and one O-H bond therefore the calculation would be: (11 412) + (4 348)+ 360 + 463 = 6747. Hexan-1-ol has 13 C-H bonds, 5 C-C bonds, one C-O bond and one O-H bond therefore the calculation would be: (13 412) + 360 + (5 348) + 463 = 7919. Heptan-1-ol has 15 C-H bonds, 6 C-C bonds, one C-O bond and one O-H bond therefore the calculation would be: (15 412) + 360 +(6 348) + 463 = 9091. Octan-1-ol has 17 C-H bonds, 7 C-C bonds, one C-O bond and one O-H bond therefore the calculation would be: (17 412) + 360 + (7 348) + 463 = 10263.
EG, if the water was 23 degrees I would heat the water to 33 degrees. Make sure that the fuel is weighed correctly after experiment, and recorded. By doing these checks, it means that all the experiments will be fun the same. This means the test will all be fair. Prediction I think the more bonds in the alcohol molecule structure means that more heat energy will be produced when the bonds are broken and so less fuel will be used, as the heating temperature will be higher, so it will not take as long to heat.
one gram of water by 1ºC. I chose to use water because it is safe,
water has risen to 60°c I will then put the lid on the spirit burner
...ise architecture at the time is undoubtedly one of his greatest achievements. Louis Sullivan gave light to the phrase, ‘form follows function,’ however, one could argue this to be hypocritical coming from the man who focused to heavily on ornamentation. Through in depth research, this discussion successfully concludes that, as Sullivan himself stated, a building that bears no decoration could be a magnificent building. Then again, in terms of the Wainwright building, when the ornamentation and construction turn into one, the building is likewise magnificent.
the same will be the height of the tin can above the wick. I will keep
This software enables you to simulate experiments. This means that I am able to quickly carry out experiments to help in planning for my investigation. ---------------------------------------------------------------------- Alcohol Temperature Increase (oC) Mass of burner before exp. (g) Mass of burner after exp.
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