Question

Three gases (8.00 g of methane, CH4, 18.0 g of ethane, C2H6, and an unknown amount of propane, C3H8) were added to the same 10.0-L container. At 23.0 ∘C, the total pressure in the container is 4.60 atm . Calculate the partial pressure of each gas in the container. Express the pressure values numerically in atmospheres, separated by commas. Enter the partial pressure of methane first, then ethane, then propane.

Answer 1

i) Calculate total number of moles using ideal gas equation

PV = nRT

n = PV/RT

= 4.60atm × 10.0L /(0.082057(L atm/mol K) × 296.15K)

= 1.8929mol

ii) Calculate the number of moles of metane and ethane

number of moles = mass/molar mass

number of moles of methane = 8.00g/16.043g/mol = 0.4987mol

number of moles of ethane = 18.0g / 30.07g/mol = 0.5986mol

ii) Calculate number of moles of propane

number of moles of propane = Total number of moles - (Number of moles of methane + Number of moles of ethane) Number of moles of propane = 1.8929mol - (0.4987mol + 0.5986mol) = 0.7956mol

iv) calculate mole fractions of methane, ethane and propane

mole fraction = number of molese /Total number of moles

mole fraction of methane = 0.4987mol/1.8929mol = 0.2635

mole fraction of ethane = 0.5986mol/1.8929mol = 0.3162

mole fraction of propane = 0.7956mol/1.8929mol = 0.4203

v) calculate partial pressures

partial pressure = mole fraction × Total pressure

Partial pressure of methane = 0.2635× 4.60atm = 1.212atm

partial pressure of ethane = 0.3162× 4.60atm = 1.455atm

partial pressure of propane = 0.4203 × 4.60atm = 1.933atm