Question

How long would it take for 2.2 x 10^-4 mol H2 to effuse through the same orifice as the 2.2x 10^-4 mol N2? (It takes 105s for N2 to effuse)

I was thinking of setting up the equation like: sqroot(28.014gN2/mol / 2.016g H2/mol) = 3.728

What should I do next? Also, when setting up the ratio of the molar masses, does the heavier molar mass always go on top?

Answer 1

If you call H2 = gas 1 and N2 = gas 2, then M1 = molar mass H2 and M2 = molar mass N2.
Then rate H2/rate N2 = (sqrt(M2/M1)
[(2.2E-4/x)/(2.2E-4/105)] = sqrt (28/14)
[(1/x)/(1/105)] = 3.728
1/x = 3.728*(1/105)
105 = 3.728*x
x = 105/3.728 = about 28 seconds which makes since. The lower molar mass will effuse faster than the higher molar mass material.

Answer 2

Oh, so to get the rate of a gas, you do moles divided by the time?

Answer 3

yes, rate is L/time or mols/time as so many liters/second or liters/min or liters/hr etc.