Measuring moles of GASES by measuring their volumes

Experiments show that

at room temperature and pressure

one mole of ANY gas occupies 24dm3 (24000cm3)

Hence, if the volume of a gaseous sample is measured, at room temperature and pressure, the number of moles (n) of gas in the sample can be calculated using

n = Vdm3 / 24

What is the volume (cm3) of 3g of ethane gas at rtp?

Molecular Formula of ethane = C2H6

Moles = mass = 3/30 = 0.1 moles

Molar massVol = 24000 x No of moles. Answer = 2400cm3

6g of a hydrocarbon gas had a volume of 4.8 dm3. Calculate its Molar Mass.

Moles = Volume/24dm3 = 4.8/24 = 0.2Molar mass = Mass/moles =6/0.2Answer 30

Q1

Calculate the number of moles present, if a

gas sample has a volume of 20.0 dm3 at

room temperature and pressure.n = Vdm3 / 24

= 0.833 moles

= 20 / 24

n = Vdm3 / 24

= 0.00417 moles

= 0.100 / 24

Q2 a sample of gas weighs 0.272g. It has a volume of

100cm3 at a room temperature pressure. Calculate the

number of moles of gas in the sample and hence the

mass of one mole of the gas.

Mass of one mole = 0.2720.00417

= 65.2 g