if the effusion rate of Methane (CH4) through hole in the tank is 3.5x10^-4 mol in 15 min and the temperature is 200 degrees Celsius.
which part of Ethane will go through the same hole in 25 min in the same temperature ?

what I not sure is what formula I need to use for this question.

thanks.

Okay, I had to look that up, and that's more about chemistry, lol :p

Anyway, wikipedia says:

\frac{R_1}{R_2} = \sqrt{\frac{M_2}{M_1}}

Hm... seems really easy, doesn't it? :)

\frac{3.5\times 10^{-4} / 15}{R_2} = \sqrt{\frac{30}{16}}

Then work out the number of moles.

Rate = Moles / Time

Oh and source: http://en.wikipedia.org/wiki/Graham%27s_Law_of_Effusion

Hi thanks for help. I was sure is will be correct to post it in physics :)

So you told me to work out the number of moles from this formula:Rate=moles/time.

So if the Rate for the first formula is 1.369.
I only need to know what time I need to put in this formula? The 15 min or 25 min? Or both :)
I guess I need to use the time of the Ethane what mean I need to use the 25 min.
So I need to do rate*time=mole ? Do I get closer?

How did you get that rate? :confused:

Rate * Time = Mole

Rate * 15 = 3.5x10^-4

Rate = 3.5*10^-4/15 = 0.000023333 = 2.33x10^-5 mol/min

Ohh OK OK now I see . :)
Well thank you for helping.
Really thanks.