1. Molecular Weight Determination of Butane Gas
General Chemistry 101/102 Laboratory Manual University of North Carolina at Wilmington

2. MW Determination of Butane Gas
Purpose
Determine the molecular weight (molar mass) of a gas from information about its mass, volume, temperature, and pressure.
Demonstrate applications of the Ideal Gas Law and Dalton’s Law of Partial Pressures.
Safety Considerations
Butane gas is very flammable. There should be no open flames in the laboratory during this experiment.

3. MW Determination of Butane Gas
Procedure
Fill a baby bottle with water to the very top.
Cover the bottle with a glass plate.
Invert the bottle in a pneumatic trough and carefully remove the glass plate.

4. MW Determination of Butane Gas
Procedure
Insert the tube from the butane canister under the lip of the inverted baby bottle.
Release approximately 200 mL of gas into the bottle by pressing straight down on the valve. Do not displace all of the water from the bottle.
Push straight down

5. MW Determination of Butane Gas
Procedure
Raise and/or lower the baby bottle until the water level in the bottle is even with the water level in the trough, then read the volume of the gas from the graduations on the bottle.
Water level in bottle lined up with water level in trough

6. MW Determination of Butane Gas
Formulas and Equations
g R T
M =
P V
P =
P P
water
total
butane