Question

A flammable hydrocarbon gas of particular volume is found to diffuse through a small hole in 1.5 minutes. Under the same conditions of temperature and pressure an equal volume of bromine vapour takes 4.73 min to diffuse through the same hole. Calculate the molar mass of the unknown gas and suggest what this gas might be, (Given that molar mass of bromine = 159.8 g/ mole)

Answer 1

t₁ = 1.5 minutes (gas)_hydrocarbon 

t₂ = 4.73 minutes (gas)_Bromi 

n(12) + (2n + 2)1 = 16 (general formula for hydrocarbon C_nH_2n+2)

12n + 2n + 2 = 16 

14n = 16 – 2 

14n = 14 

n = 1 

The hydrocarbon is C₁H_{2(1) + 2} = CH₄