Combustion Of Alkanols
Heats of Combustion of Alkanols
Aim: To perform a first-hand investigation to determine the heats of combustion of selected alkanols.
Hypothesis: It was predicted that methanol would have the highest molar heat of combustion, decreasing as the chains become longer.
Equipment:
• Three spirit burners containing methanol, ethanol and propan-1-ol respectively • Electronic scales • Water • 100ml measuring cylinder • Retort stand and boss-head clamp • Copper beaker • Thermometer
Method:
1. All three of the spirit burners were weighed separately and their masses recorded. 2. 100ml of water was measured out and placed in the copper beaker, which was then suspended with the boss-head clamp above the methanol spirit burner. …show more content…
The methanol spirit burner was lit, and the temperature raise in the water was observed until a 10 oC rise in the original temperature was noticed. The spirit burner was then extinguished. 4. The spirit burner was re-weighed and the mass again recorded to determine the mass loss. 5. Steps 2-4 were repeated with each of the other spirit burners. 6. Results were collected and used to determine the molar heat of combustion for each of the alkanols.
Results:
|Alkanol |Initial Mass (g) |Final Mass (g) |Mass Change (g) |
|Methanol |176.5 |176.0 |0.5 |
|Ethanol |172.8 |172.5 |0.3 |
|Propan-1-ol |178.7 |178.4 |0.3 |
Discussion:
Error was ignored in this experiment due to heat loss to the environment, …show more content…
There are several reasons for these vast discrepancies. Firstly, the scientifically accepted results were calculated in a bomb calorimeter, a completely closed system. With the equipment available in the school laboratory, this kind of accuracy was impossible. There was no way of ensuring that the heat from the spirit burner only heated the copper beaker, instead of the surrounding environment. This dispersion of heat was the largest source of error in the experiment, and the reason for obtaining values significantly lower than those of other trials.
Secondly, there was no way of ensuring the test was conducted in Standard Laboratory Conditions (SLC), or even if all alkanols were tested in the same conditions. This will have caused slight discrepancies in the results, although with the accuracy of the overall experiment, this error is insignificant.
Thirdly, when the cap is off the spirit burner, the alkanol can escape; causing a mass change that was not as a result of the burning. Although all care was taken to reduce the time when the cap was off, there still will have been some error resulting from this. However, in light of the inaccuracy caused by the first error, this error is quite
Aim: To perform a first-hand investigation to determine the heats of combustion of selected alkanols.
Hypothesis: It was predicted that methanol would have the highest molar heat of combustion, decreasing as the chains become longer.
Equipment:
• Three spirit burners containing methanol, ethanol and propan-1-ol respectively • Electronic scales • Water • 100ml measuring cylinder • Retort stand and boss-head clamp • Copper beaker • Thermometer
Method:
1. All three of the spirit burners were weighed separately and their masses recorded. 2. 100ml of water was measured out and placed in the copper beaker, which was then suspended with the boss-head clamp above the methanol spirit burner. …show more content…
The methanol spirit burner was lit, and the temperature raise in the water was observed until a 10 oC rise in the original temperature was noticed. The spirit burner was then extinguished. 4. The spirit burner was re-weighed and the mass again recorded to determine the mass loss. 5. Steps 2-4 were repeated with each of the other spirit burners. 6. Results were collected and used to determine the molar heat of combustion for each of the alkanols.
Results:
|Alkanol |Initial Mass (g) |Final Mass (g) |Mass Change (g) |
|Methanol |176.5 |176.0 |0.5 |
|Ethanol |172.8 |172.5 |0.3 |
|Propan-1-ol |178.7 |178.4 |0.3 |
Discussion:
Error was ignored in this experiment due to heat loss to the environment, …show more content…
There are several reasons for these vast discrepancies. Firstly, the scientifically accepted results were calculated in a bomb calorimeter, a completely closed system. With the equipment available in the school laboratory, this kind of accuracy was impossible. There was no way of ensuring that the heat from the spirit burner only heated the copper beaker, instead of the surrounding environment. This dispersion of heat was the largest source of error in the experiment, and the reason for obtaining values significantly lower than those of other trials.
Secondly, there was no way of ensuring the test was conducted in Standard Laboratory Conditions (SLC), or even if all alkanols were tested in the same conditions. This will have caused slight discrepancies in the results, although with the accuracy of the overall experiment, this error is insignificant.
Thirdly, when the cap is off the spirit burner, the alkanol can escape; causing a mass change that was not as a result of the burning. Although all care was taken to reduce the time when the cap was off, there still will have been some error resulting from this. However, in light of the inaccuracy caused by the first error, this error is quite