A 10.0 L flask at 318 K contains a mixture of Ar and CH4 with a total pressure of 1.040 atm. If the mole fraction of Ar is 0.715, what is the mass percent of Ar?

Explanation:

Hello,

In this case, given the temperature, volume and total pressure, we can compute the total moles by using the ideal gas equation:

Next, using the molar fraction of argon, we compute the moles of argon:

And the moles of methane:

Now, by using the molar masses of both argon and methane, we can compute the mass percent of argon:

Regards.