diffusion rate of methane gas compared to that of helium is...

[Smooth Operater]

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the diffusion rate of methane gas compared to that of helium is

a. twice as fast
b. 4 times as slow
c. 4 times as fast
d. half as fast
e. 12 times as fast.

I tried to use r1/r2 = (M2/M1)^1/2 to solve this, but it gives me 4 times as slow. But the acctual answer from Barron is "D". how would you calculate this?

 

[JohnDoeDDS]

dunno how you are getting four but the answer is definately a half. Here is how.

Since you are comparing CH4 to HE CH4=rate1 and He= rate 2.

So...

CH4/He = sqrt(4/16) This translates to sqrt(4)/sqrt(16) = 2/4 = 1/2