Standard level
Avogadro's law tells us the the volume of a gas is directly proportional to the volume occupied. The ideal gas equation allows us to determine the number of moles of gas under different conditions of temperature and pressure.
Background
If a known mass of a volatile liquid is heated beyond its boiling point, then measurement of the volume can be used to determine the number of moles present, providing that the temperature and pressure are also known.
The ideal gas equation
PV = nRT
Where:
- P is pressure in kPa
- V is volume in dm3
- T is the absolute temperature
- R is the universal gas constant, 8.31 J K-1 mol-1
The moles of gas present, n, can then be used to determine the relative mass of the gas.
Relative mass determination
Relative mass = mass/mol
- After reading the animation above, advance to the second page and follow the instructions.
- Take care to convert any data that is not in suitable units.
- First click on the syringe and once the volatile liquid is injected, click on the oven's on button.
- Record your data, convert the units and determine the relative mass.
- Check your answer using the return key.
- Record at least 5 sets of data.
The animation can be projected full screen here.