Stand
Alcohol burner
Heatproof
Fig 1.
The apparatus to measure enthalpy change
3.Pour the water from the measuring cylinder into the copper can, which is on the stand and clamped in position, and put a thermometer into the water to measure the temperature change.
4.Weigh the alcohols that are to be investigated, and record the weight.
5.Place the alcohol burner under the copper can, which is on the stand.
6.Ignite the burner with a match to heat the copper can, which contains water.
7.Place the heatproof mal around the apparatus to prevent the loss of heat energy.
8.Observe the thermometer and when the water temperature has raised 20C, remove the source of heat by placing the cover over the top of the burner.
9.Remove the burner, place it on the balance, and record the weight of the alcohol, then calculate the weight of alcohol used.
10.Calculate the enthalpy change of alcohol.
11.Repeat the above steps by using a fresh sample of water for investigate each one of the alcohols (methanol ethanol butan-1-ol and propan-1-ol, I choose them they are all primary alcohols with straight chains, only differ by CH2 chains), and record the results.
12.Calculate and compare the enthalpy change of the alcohols under investigation.
Risk assessment
Extreme caution must be exercised when handling inflammable liquids such as alcohols especially when a naked flame is also being used.
Precautions:
-Eye protection (goggles)
-Hair should be tied back
-Ties must be tucked into the shirt
-Loose clothing must be removed
-Working area must be clean
-Keep away from naked flame
Why the plan is reliable
This plan has been written in sufficient detail with emphasis on accuracy in measurement and observation to allow anyone who has no previous experience of this experiment to carry it out competently. The steps described in the method are detailed and clear and progress from setting up the experiment to obtaining results.
Result tables
This is the result table of the weight of the alcohols used for rising up 20C of water (from 21C to 41C)
This is the result table of the changing in temperature
Calculations
The beginning temperature is 21C
4.17 X 200 X 20 = 16680J=16.68KJ
Methanol:
Hc = 16.68 X 32 / 1.23 = 433.95kJ/mol-1
The Hc of methanol is 433.95KJ/mol-1
Ethanol:
Hc = 16.68 X 46 / 0.90 = 852.53KJ/mol-1
The Hc of ethanol is 852.53KJ/mol-1
Propan-1-ol:
Hc =16.68 X 60 / 0.81 = 1235.56KJ/mol-1
The Hc of propan-1-ol is 1235.56KJ/mol-1
Butan-1-ol:
Hc = 16.68 X 74/0.69 = 1788.87KJ/mol-1
The Hc of butan-1-ol is 1788.87/KJmol-1
Procedural errors
The official values of the energy produce by methanol, ethanol, butan-1-ol and propan-1-ol are half data above my results, because nearly half of the heats come in to the atmosphere, and incomplete combustion exists in this experiment, as we can see the soot on the bottom of the copper can after the combustion.
Evaluation
To make this experiment more accrual, I have to:
-When I add water to the measuring cylinder, I have to make sure base of the meniscus of the solution was at the level of the calibration line on the measuring cylinder.
-Place the heatproof mal around the apparatus to prevent the loss of heat energy.
-Use fresh sample of water to investigate each one of the alcohols, make sure there is no water left in the copper can before you investigate a new alcohol.
percentage Errors
Mass of methanol burner (reading):
Before the combustion
+/- 0.005 / 232.39 x 100 % = 0.0021 %
After the combustion
+/- 0.005 / 231.16 x 100 % = 0.0021 %
Mass of the ethanol burner (reading):
Before the combustion
+/- 0.005 / 231.41 x100 % = 0.0021 %
After the combustion
+/- 0.005 / 230.51 x100 % = 0.0021 %
Mass of the propan-1-ol burner (reading):
Before the combustion
+/- 0.005 / 248.30 x100 % = 0.0020 %
After the combustion
+/- 0.005 / 247.49 x100 % = 0.0020 %
Mass of the butan-1-ol burner (reading):
Before the combustion
+/- 0.005 / 247.46 x100 % = 0.0020 %
After the combustion
+/- 0.005 / 246.77 x100 % = 0.0020 %
Measuring cylinder:
+/- 0.5 / 200 X 100 % = 0.25 %
Temperature:
+/- 0.5 / 20.0 X 100 % = 2.5 %
Conclusion
The generalized equation for the combustion of alcohols is:
Alcohol + Oxygen Carbon dioxide + Water
The longer chain molecules such as butan-1-ol and propan-1-ol can produce more energy than shorter chain molecules like methanol and ethanol, because the energy is contained in the bonds, Therefore an alcohol with the greatest number of carbons will have greatest amount of energy, and will produce the increase in temperature for the least amount of fuel used.
Reference
Heinemann, Salters Advanced Chemistry, Chemical idea (Second Edition), Central Team George, Burton, John Holman, John Lazonby, Gwen Pilling and David Waddington
