Results:
Table: Mass of alcohols combusted along with experimental and literary values for enthalpy change
Alcohol Molar Mass (g/mol) Mass of Alcohol Combusted (g) Enthalpy (kJ/mol) Enthalpy literature value [Stretton n.d.]
(kJ/mol)
Trial 1 Trial 2 Trial 3 Average (mean) Trial 1 Trial 2 Trial 3 Average (mean)
Ethanol 46.07 1.447 1.327 1.371 1.382 -133.1 -145.1 -140.5 -139.3 -1367
Propanol 60.10 1.133 1.375 1.255 1.254 -221.7 -182.7 -200.2 -200.3 -2021
Butanol 74.12 1.181 1.046 1.119 1.115 -262.3 -296.2 -276.9 -277.9 -2676
Pentanol 88.15 1.047 1.006 1.166 1.073 -351.9 -366.3 -316.0 -343.4 -3329
Hexanol 102.2 0.7920 0.9940 1.014 0.9333 -539.2 -429.6 -421.2 -457.6 -3984
Sample Calculation:
The enthalpy is calculated using the following formula, …show more content…
When the alcohol burners were in use, the heat energy could not have been completely transferred to the water and would have been transformed into another form. There are three different mediums that the heat energy was likely transferred into. The first and most significant would be the air, the second would have been the metal tripod, and the third would have been the glass beaker (excluding the water). The impact of this error could be decreased through performing the experiment in an insulated container with a lid as it would prevent the heat from escaping the enclosed space and as a result some of it would be transferred to the water.
One major source of random error is an error of parallax occurring during several measurements. The first scenario was when the beakers were filled 100ml of distilled water. It likely that at least several beakers may have been filled slightly above or below the 100ml marker, and if so would have slightly altered the measurement of water. This error could be minimised through the use of measuring cylinders and pipettes in order to accurately measure out 100ml, although it would likely only improve the accuracy …show more content…
The tripod that held the beaker was in the direct path of the heat energy released during the combustion and as a result some of the heat energy would have been absorbed by it. Although the effect on the initial samples would have been small, if not insignificant, the cumulative effect would eventually result in the tripod having a temperature significantly higher than the water and its temperature could have acted as a secondary source of heat energy when increasing the temperature of the water. A method to minimise the impact of this error would be to periodically switch the tripod with another identical one, which almost completely negate the effect of the additional heat
Table: Mass of alcohols combusted along with experimental and literary values for enthalpy change
Alcohol Molar Mass (g/mol) Mass of Alcohol Combusted (g) Enthalpy (kJ/mol) Enthalpy literature value [Stretton n.d.]
(kJ/mol)
Trial 1 Trial 2 Trial 3 Average (mean) Trial 1 Trial 2 Trial 3 Average (mean)
Ethanol 46.07 1.447 1.327 1.371 1.382 -133.1 -145.1 -140.5 -139.3 -1367
Propanol 60.10 1.133 1.375 1.255 1.254 -221.7 -182.7 -200.2 -200.3 -2021
Butanol 74.12 1.181 1.046 1.119 1.115 -262.3 -296.2 -276.9 -277.9 -2676
Pentanol 88.15 1.047 1.006 1.166 1.073 -351.9 -366.3 -316.0 -343.4 -3329
Hexanol 102.2 0.7920 0.9940 1.014 0.9333 -539.2 -429.6 -421.2 -457.6 -3984
Sample Calculation:
The enthalpy is calculated using the following formula, …show more content…
When the alcohol burners were in use, the heat energy could not have been completely transferred to the water and would have been transformed into another form. There are three different mediums that the heat energy was likely transferred into. The first and most significant would be the air, the second would have been the metal tripod, and the third would have been the glass beaker (excluding the water). The impact of this error could be decreased through performing the experiment in an insulated container with a lid as it would prevent the heat from escaping the enclosed space and as a result some of it would be transferred to the water.
One major source of random error is an error of parallax occurring during several measurements. The first scenario was when the beakers were filled 100ml of distilled water. It likely that at least several beakers may have been filled slightly above or below the 100ml marker, and if so would have slightly altered the measurement of water. This error could be minimised through the use of measuring cylinders and pipettes in order to accurately measure out 100ml, although it would likely only improve the accuracy …show more content…
The tripod that held the beaker was in the direct path of the heat energy released during the combustion and as a result some of the heat energy would have been absorbed by it. Although the effect on the initial samples would have been small, if not insignificant, the cumulative effect would eventually result in the tripod having a temperature significantly higher than the water and its temperature could have acted as a secondary source of heat energy when increasing the temperature of the water. A method to minimise the impact of this error would be to periodically switch the tripod with another identical one, which almost completely negate the effect of the additional heat