How To Determine The Molar Mass Of Butane
Practical 6 -Determining the Gas Constant
Aim:
To verify the gas constant as 8.31 J/mol/K ( ) and to calculate the molar mass of butane.
Theory:
The ideal gas law, PV=nRT, is used to model an ideal gas, which is a gas with no intermolecular forces other than those of collisions, perfectly spherical and elastic particles. Although an ideal gas is a theoretical model and so cannot exist in practice, most gases behave fairly similarly to an ideal gas. Gases behave more like an ideal gas when they are at a higher temperature and lower pressure, as the potential energy of the intermolecular forces becomes negligible compared to the kinetic energy of the gas.
Butane gas does follow the ideal gas law fairly well, as it is non-polar and hence has …show more content…
Raw Data:
Value Uncertainty Propagations Final Uncertainty
Temperature (of water) °K = 18.4 °C
= (18.4+273.2) °K
= 291.6 °K Uncertainty of 18.4 °C is ± 0.5 °C
(Half of the smallest interval on an analogue scale)
Converting to relative uncertainty
= ± (0.5/18.4) × 100%
= ± 2.717391304%
(Relative uncertainty is same for measurement in Kelvin since the conversion uses an exact value) ≈ ± 3%
Volume of gas (m3) = 237 mL
= (237/1000/1000) m3
= 0.000237 m3 Uncertainty of 237 mL is ± 1 mL
(Half of the smallest interval on an analogue scale)
Converting to relative uncertainty
= ± (1/237) × 100%
= ± 0.4219409283%
(Relative uncertainty is the same for measurement in m3 as the conversions uses exact values) ≈ ± 0.4%
Initial mass of lighter - Mi (kg) = 24.320 g
= (24.320/1000) kg
= 0.02432 kg Uncertainty of 24.320 g is ± 0.001 g
(Number of decimal places on a digital scale)
Converting to relative uncertainty
= ± (0.001/24.320) × 100%
= ± 0.004111824105 %
(Relative uncertainty is the same for measurement in kg as the conversion uses an exact value) ≈ ± 0.0004%
Final mass of lighter - Mf
(kg) = 23.677 g
= (23.677/1000) kg
= 0.023677 kg Uncertainty of 23.677 g is ± 0.001 g
(Number of decimal places on a digital …show more content…
This indicates the presence of systematic error in the experiment.
The experimental value for the molar mass of butane was 66 ±2 g/mol, with the literature value of 58.122 g/mol not lying within this uncertainty and a percentage error of about 13%. This indicates the presence of systematic error in this experiment too.
A potential follow-up experiment could be to use an alternative gas to do the experiment, such as propane, or to alter the temperature of the gas to see the change in volume.
Evaluation:
Sources of
Aim:
To verify the gas constant as 8.31 J/mol/K ( ) and to calculate the molar mass of butane.
Theory:
The ideal gas law, PV=nRT, is used to model an ideal gas, which is a gas with no intermolecular forces other than those of collisions, perfectly spherical and elastic particles. Although an ideal gas is a theoretical model and so cannot exist in practice, most gases behave fairly similarly to an ideal gas. Gases behave more like an ideal gas when they are at a higher temperature and lower pressure, as the potential energy of the intermolecular forces becomes negligible compared to the kinetic energy of the gas.
Butane gas does follow the ideal gas law fairly well, as it is non-polar and hence has …show more content…
Raw Data:
Value Uncertainty Propagations Final Uncertainty
Temperature (of water) °K = 18.4 °C
= (18.4+273.2) °K
= 291.6 °K Uncertainty of 18.4 °C is ± 0.5 °C
(Half of the smallest interval on an analogue scale)
Converting to relative uncertainty
= ± (0.5/18.4) × 100%
= ± 2.717391304%
(Relative uncertainty is same for measurement in Kelvin since the conversion uses an exact value) ≈ ± 3%
Volume of gas (m3) = 237 mL
= (237/1000/1000) m3
= 0.000237 m3 Uncertainty of 237 mL is ± 1 mL
(Half of the smallest interval on an analogue scale)
Converting to relative uncertainty
= ± (1/237) × 100%
= ± 0.4219409283%
(Relative uncertainty is the same for measurement in m3 as the conversions uses exact values) ≈ ± 0.4%
Initial mass of lighter - Mi (kg) = 24.320 g
= (24.320/1000) kg
= 0.02432 kg Uncertainty of 24.320 g is ± 0.001 g
(Number of decimal places on a digital scale)
Converting to relative uncertainty
= ± (0.001/24.320) × 100%
= ± 0.004111824105 %
(Relative uncertainty is the same for measurement in kg as the conversion uses an exact value) ≈ ± 0.0004%
Final mass of lighter - Mf
(kg) = 23.677 g
= (23.677/1000) kg
= 0.023677 kg Uncertainty of 23.677 g is ± 0.001 g
(Number of decimal places on a digital …show more content…
This indicates the presence of systematic error in the experiment.
The experimental value for the molar mass of butane was 66 ±2 g/mol, with the literature value of 58.122 g/mol not lying within this uncertainty and a percentage error of about 13%. This indicates the presence of systematic error in this experiment too.
A potential follow-up experiment could be to use an alternative gas to do the experiment, such as propane, or to alter the temperature of the gas to see the change in volume.
Evaluation:
Sources of