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Determining relative molecular masses by weighing gases

Description

In this experiment known volumes of different gases are weighed in a gas syringe and their relative molecular masses are determined using the ideal gas equation.

Type of Activity

:
demonstration, class practical

Audience

:
Teacher

Age Group

:
11 to 18 years

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
determining-relative-mole...



Apparatus Chemicals

Eye protection

Syringe, plastic disposable, 50 cm3 (larger if available) fitted with hypodermic needle (Note 1)

Small rubber bung (exact size unimportant)

Nail, 5 cm long

For each gas bag (Note 2):

Polythene bag (sandwich or freezer bag), capacity 1 to 2 dm3

Rubber bung, one-hole, 17 mm or similar

Glass tubing, 4 - 5 cm length, to fit rubber bung

Rubber septum cap, self-sealing, to fit the glass tubing

Cable tie (to fit around the rubber bung)

Top-pan balance, accurate to +/- 0.001 g (Note 3)

Thermometer to measure room temperature, accurate to +/- 0.5 ºC (digital display if available)

Access to an accurate measurement of atmospheric pressure

Gas bags filled with various gases:

Hydrogen (EXTREMELY FLAMMABLE)

Oxygen (OXIDISING)

Nitrogen

Methane (natural gas) (EXTREMELY FLAMMABLE)

Carbon dioxide

Refer to Health & Safety and Technical notes section below for additional information.

 

 




 





In this experiment known volumes of different gases are weighed in a gas syringe and their relative molecular masses are determined using the ideal gas equation.

ADDITIONAL INFORMATION

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology.