A mixture of methane and hydrogen gases contains methane at a partial pressure of 403 mm Hg and hydrogen at a partial pressure of 501 mm Hg. What is the mole fraction of each gas in the mixture?

Question

A mixture of methane and hydrogen gases contains methane at a partial pressure of 403 mm Hg and hydrogen at a partial pressure of 501 mm Hg. What is the mole fraction of each gas in the mixture?



Answer 1

Notice how there is no addtional information is given other than the partial pressures. Not to worry because we can put in anything in for the temperature and volume so we can use PV=nRT at ST (Standard Temperature - 273K).

For volume we can use the volume on emole of gass occuoies at STP which is 22.4 Liters.

So we want to solve for n so we can use n=PV/RT.

# of moles of methane:

n=(403/760)x22.4/0.08205x273 = 0.530 moles

# moles of hydrogen:

n=(501/760)x22.4/0.08205x273 = 0.659 moles

So the total number of moles is 1.189 moles

The mole fraction of methane is 0.530/1.189 = 0.446

The mole fraction of Hydrogen is 1.000 - 0.446 = 0.554