Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: gyromag on May 01, 2006, 08:03:12 PM

Title: Ideal gases: calculating Mol ratio
Post by: gyromag on May 01, 2006, 08:03:12 PM
Greetings,

I am having difficulty with calculating the mol ratio of argon (MW 39.95) to nitrogen (28.01) if the calculated MW is 28.15.  This problem is taken from Zumdahl's Chemical Principals 2nd Ed. (Chapter 5 #29) and the answer is given at the back of the book as 1.18 X 10^-2.  Can someone nudge me in the right direction on how to arrive at this response?  Thanks!
Title: Re: Ideal gases: calculating Mol ratio
Post by: Borek on May 01, 2006, 08:32:13 PM
Try with molar fractions (http://www.chembuddy.com/?left=concentration&right=molar-fraction).

Assuming there is x of one and (1-x) of another, calculated molar mass is 39.95x + (1-x)*28.01.
Title: Re: Ideal gases: calculating Mol ratio
Post by: tennis freak on May 09, 2006, 09:43:07 PM
to do this wouldnt you need to know how many moles of each there were in the reaction? and where does that mass come from anyway?
Title: Re: Ideal gases: calculating Mol ratio
Post by: Borek on May 10, 2006, 03:57:48 AM
There is no reaction here, there is a mixture of two gases that behaves like gas of given molar mass.
Title: Re: Ideal gases: calculating Mol ratio
Post by: Donaldson Tan on May 11, 2006, 08:51:13 AM
let mol% of Argon be x

=> mole% of Nitrogen = 1 - x

Average Molar Mass = x*(molar mass of Argon) + (1-x)*(molar mass of N2)

Solve for x