# Simple gas effusion question

#### sphys2017

I can't seem to work out question 107. I can do 106 and 108. I keep getting B for 108 but the answer is A Can you see the link, if not here it is http://m.imgur.com/a/TQ8MS sorry

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#### topsquark

Forum Staff
I can't seem to work out question 107. I can do 106 and 108. I keep getting B for 108 but the answer is A Can you see the link, if not here it is Imgur: The most awesome images on the Internet sorry
It seems to me that you are trying to talk about Graham's equation? If that's then the d's aren't supposed to be differentials, right? If that's the case then yes, your work is correct.

(The d's leading to dy/dx seems to imply partial derivatives. If that's the case then formally speaking, no you can't do that.)

-Dan

#### sphys2017

Yes it's Graham's equation. So the dx denotes density for atom X and dy denotes the density for atom Y. So apparently the answer is A because rate and time are inverses. So I had to switch op and bottom to get the correct ratio.

#### topsquark

Forum Staff
Yes it's Graham's equation. So the dx denotes density for atom X and dy denotes the density for atom Y. So apparently the answer is A because rate and time are inverses. So I had to switch op and bottom to get the correct ratio.
Then yes, you did it right. Good job.

-Dan