A 6.0 L flask contains a mixture of methane, argon and helium at 45 degrees C and 1.75 am. If the mole fractions of helium and argon are 0.25 and 0.35, respectively, how many molecules of methane are present?
total mole fraction = 1.00 (always)
XHe + XAr + XCH4 = 1.00
Solve for XCH4.
Then PCH4 = XCH4*Ptotal
Use PV = nRT to solve for n
Then remember there are 6.022E23 molecules in 1 mole.