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bluegreen

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## Homework Statement

From Atkins Physical Chemistry text, 9th Edition:

1.7b) The following data has been obtained for oxygen gas at 273.15 K. Calculate the best value of the gas constant R from them and the best value of the molar mass of O2 (oxygen).

p(in atm)

P1=0.750 000

P2= 0.500 000

P3=0.250 000

Vm [molar volume] (in dm^3/mol)

Vm1= 29.8649

Vm2=44.8090

Vm3=89.6384

## Homework Equations

## The Attempt at a Solution

To find R, I used R= (Vm P)/ T to find the different Rs for each set of data, then used y=mx+b (using data points [P, R]) to extrapolate back to when p=0 (when ideal gas is most accurate; so that means the y intercept which was equivalent to R).

I know you can just graph it and get the same result. Either way, I got R= 0.0820614 dm^3 atm/K mol.

Now I'm lost. How do I set it up to find molar mass? Do I extrapolate using a graph again? I'm not given density, so it throws a wrench in a lot of the equations I tried using, like:

Vm= M/ density = RT/P= V/n