The Pressure will be considered as the atmospheric pressure of Bogota which is 75 kPa which equals 75000 Pa, the value of the pressure will now only be considered in SI units.
ANALYSIS OF RESULTS:
In order to calculate the number of moles of gas present in the flask we can use the law of ideal gases which is expressed with the following equation:
Which can be rearranged in order to have as the subject, as shown below.
Where is pressure, is volume, is temperature, is a constant and is the number of moles of the gas.
To use this law we can consider the following values for volume, pressure and temperature; the value of the constant is 8.314 when working with SI units.
Temperature: 365±0.1⁰K
Volume: 3.25x10-4 ± 2.5x10-6 m3
Pressure: 75000 Pa
So if we use the previously established values in the equation we will get the number of moles of gas inside the flask.
To calculate the percentage uncertainty of this value we need to add up the percentage uncertainty of the pressure, the temperature and the volume
Percentage uncertainty of the volume
Uncertainty: ± 2.5 x 10-6 m3
Volume: 3.25 x 10-4 m3
Percentage uncertainty = 0.77%
Percentage uncertainty of the temperature
Uncertainty: ±0.1⁰K
Temperature: 365⁰K
Percentage uncertainty = 0.03%
So the percentage uncertainty of the number of moles of the gas is of 0.8%.
Number of moles of gas:
Now in order to calculate the molar mass of the gas we divide the mass of the gas registered in Table 1 by the number of moles that we have just calculated.
To calculate the percentage uncertainty of this value we need to add up the percentage uncertainty of the mass and of number of moles.
Percentage uncertainty of the mass
Uncertainty: ±0.01g
Mass: 0.80g
Percentage uncertainty = 1.25%
The percentage uncertainty of the molar mass would then be of 2.05%.
CONCLUSION:
Taking in count that the liquid used in this experiment was a cycloalkane and that the empirical formula of cycloalkanes is, we can determine what cycloalkane was used by just dividing the molar mass of the liquid by the empirical mass of cycloalkanes.
The result of this division was 7.1 which tells us that the molecular formula for the cycloalkane used in the experiment is which is the molecular formula for cycloheptane, therefore we can conclude that the cycloalkane used in this practical was cycloheptane.
EVALUATION:
The total percentage uncertainty of this practical was of 2.05% which is a really small percentage which makes our results very accurate.
However I can suggest repeating the practical for 2 or 3 times so that an average of the results can be obtained and the possibility of a random error can be reduced.
