Determining The Molar Mass of a Gas (HL Chemistry Lab IV)
I. INTRODUCTION
Butane (C4H10) is a colorless and almost odorless hydrocarbon gas (it has a slight
petroleum-like odor) with a molar mass of 58.124g/mol. It is a flammable gas as it can
easily react with oxygen (when subjected to high heat energy) and undergo
combustion, producing a lot of energy and carbon dioxide and water (if underwent full
combustion). Butane is used as a fuel, in cigarette lighters,
and to make other chemicals. It is not a poisonous gas,
making it an excellent option for our experiment.
Image 1 - The 2D structure of butane (C4H10). It is made of
4 carbon atoms, as shown in the image.
https://pubchem.ncbi.nlm.nih.gov
In this experiment we aim to be able to find out the molar mass of butane by performing
a series of calculations using the data we will acquire experimentally. It is relatively
simple to find out the molar mass of this compound by looking at the periodic table and
doing a few calculations, however through this lab we will see how close we can get to
the actual value (58.124 g/mol). In this lab we will come up with three volumes of
butane gas, as well as three masses (three trials will be conducted). The volume is found
by calculating the volume of water displaced by the gas (subtracting initial volume from
new one), whereas the mass will be measured by weighing the gas syringe with butane
inside it before and after using the gas to displace the water, then subtracting the new
mass from the initial mass. An average will be calculated for each of the results (mass
and volume), and these two values will be used in our calculations to reach the molar
mass of butane. The average volume will be used in the ideal gas equation to find n (the
number of moles of the gas), while the average mass will be used in the m/n calculation
to reach the final answer, where m is this average mass and n is the number of moles
, we found out doing the previous calculation. The values taken for the ideal gas
equation are the volume (V) in m3, 101.325 kPa for the pressure (P), 8.31 J/K/mol as
the universal gas constant (R), and 273 K for the temperature (T).
II. METHODOLOGY
Variables
Our dependent variable is the molar mass of butane. We will find that out by doing a
series of calculations depending on the data we get.
Our independent variable is the mass of butane used to displace the volume of water in
the graduated cylinder in each trial.
Here are the controlled variables:
Using the same source of Butane Pressure (using the same apparatus Temperature (room temperature
(same gas lighter) will enable us to maintain roughly will not be altered by keeping the
the same pressure throughout) doors and windows closed and
staying in the same room during the
experiment)
Materials
Graduated gas syringe (20 ml scale)
Graduated cylinder (10 ml scale)
Dish
Gas lighter with butane gas
Narrow rubber tube
Precision balance
Water (does not have to be distilled)
I. INTRODUCTION
Butane (C4H10) is a colorless and almost odorless hydrocarbon gas (it has a slight
petroleum-like odor) with a molar mass of 58.124g/mol. It is a flammable gas as it can
easily react with oxygen (when subjected to high heat energy) and undergo
combustion, producing a lot of energy and carbon dioxide and water (if underwent full
combustion). Butane is used as a fuel, in cigarette lighters,
and to make other chemicals. It is not a poisonous gas,
making it an excellent option for our experiment.
Image 1 - The 2D structure of butane (C4H10). It is made of
4 carbon atoms, as shown in the image.
https://pubchem.ncbi.nlm.nih.gov
In this experiment we aim to be able to find out the molar mass of butane by performing
a series of calculations using the data we will acquire experimentally. It is relatively
simple to find out the molar mass of this compound by looking at the periodic table and
doing a few calculations, however through this lab we will see how close we can get to
the actual value (58.124 g/mol). In this lab we will come up with three volumes of
butane gas, as well as three masses (three trials will be conducted). The volume is found
by calculating the volume of water displaced by the gas (subtracting initial volume from
new one), whereas the mass will be measured by weighing the gas syringe with butane
inside it before and after using the gas to displace the water, then subtracting the new
mass from the initial mass. An average will be calculated for each of the results (mass
and volume), and these two values will be used in our calculations to reach the molar
mass of butane. The average volume will be used in the ideal gas equation to find n (the
number of moles of the gas), while the average mass will be used in the m/n calculation
to reach the final answer, where m is this average mass and n is the number of moles
, we found out doing the previous calculation. The values taken for the ideal gas
equation are the volume (V) in m3, 101.325 kPa for the pressure (P), 8.31 J/K/mol as
the universal gas constant (R), and 273 K for the temperature (T).
II. METHODOLOGY
Variables
Our dependent variable is the molar mass of butane. We will find that out by doing a
series of calculations depending on the data we get.
Our independent variable is the mass of butane used to displace the volume of water in
the graduated cylinder in each trial.
Here are the controlled variables:
Using the same source of Butane Pressure (using the same apparatus Temperature (room temperature
(same gas lighter) will enable us to maintain roughly will not be altered by keeping the
the same pressure throughout) doors and windows closed and
staying in the same room during the
experiment)
Materials
Graduated gas syringe (20 ml scale)
Graduated cylinder (10 ml scale)
Dish
Gas lighter with butane gas
Narrow rubber tube
Precision balance
Water (does not have to be distilled)
