Other Learning Activity (1)
Relative Molecular Mass of Butane
Student Handout
Introduction
This activity involves the experimental determination of the relative molecular mass of a
volatile liquid. Though apparatus such as steam jacket with gas syringe is available, the
setting up is time consuming. The following design is an alternative which serves the
same purpose, but is much simpler and the experiment can be finished in much shorter
time.
Materials and Apparatus
Butane gas lighter refill cylinder
FLAMMABLE
100 cm3 gas syringe, stand and clamp, electronic balance, a short soft rubber tubing that
fits both nozzles of the syringe and the gas cylinder.
Experimental Procedures
1.
Record the room temperature and pressure.
2.
Using an electronic balance, determine the mass of the gas cylinder and the rubber
tubing.
3.
Connect the gas cylinder to a gas syringe fixed on a stand (Fig. 2). Ensure that the
joints are air-tight. Press the nozzle of the gas cylinder gently to release butane gas.
Collect about 60 cm3 of gas.
4.
Remove the gas cylinder and rubber tubing from the setup and determine their total
mass again.
5. Repeat steps (3) to (4) twice.
6. Calculate an average value for the relative molecular mass of butane, assuming that
the molar volume of a gas is 24 dm3 at r.t.p.
Fig.1
Fig. 2
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