Molar Mass of Butane
What you will need
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A lighter
Graduated cylinder
Balance
Retort stand, clamp and bosshead
Funnel
Barometer
Thermometer to measure air temperature
Thermometer to measure water temperature
What to do
1. Dip the lighter in water. Wipe as much water as possible from the lighter then weigh
the lighter to the nearest 0.01 grams.
2. Submerge a 100mL graduated cylinder in water so that the cylinder fills completely
with water. Invert the cylinder. Make sure there are no air bubbles remaining in the
graduated cylinder and fix in place using a retort stand, clamp and bosshead.
3. Flip a funnel upside down and place in the opening of the graduated cylinder.
4. Carefully release the butane from the lighter and collect in the cylinder. Release
enough gas to fill the tube to about 95mL.
5. Allow the butane to reach room temperature (about 5 minutes). Adjust the height of
the cylinder so that the height of the water inside and outside the cylinder is the
same. This makes the pressure inside and outside the cylinder the same. Record the
volume of the gas in the cylinder to the nearest mL.
6. Record the air temperature.
7. Record the water temperature.
8. Record barometric pressure in the room.
9. Remove the lighter from the water. Wipe as much water as possible from the lighter
then weigh the lighter to the nearest 0.01 grams.
10. Calculate molar mass.
11. Repeat the procedure 2 more times.
Data Sheet
Trial 1
Trial 2
Mass of lighter assembly and
contents before collection
Mass of lighter assembly and
contents before collection
Mass of the lighter assembly and
contents after collection
Mass of the butane gas evolved
Volume of gas produced at room
temperature and atmospheric
pressure
Barometric pressure
Water temperature
Vapor pressure of water at water
temperature (from table)
Partial pressure of dry butane
(show calculation)
Ptot = Pbutane + Pwater vapour
Room temperature
Molar mass of the butane (show
calculation)
M = mRT/PV
True value for the molar mass _______________________
Average molar mass for the three trials _______________
Experimental error for the average (show calculation) __________________
Trial 3