Van der Waals Equation - solve for n

Chemistry and homework help forum.

Organic Chemistry, Analytical Chemistry, Biochemistry, Physical Chemistry, Computational Chemistry, Theoretical Chemistry, High School Chemistry, Colledge Chemistry and University Chemistry Forum.

Share your chemistry ideas, discuss chemical problems, ask for help with scientific chemistry questions, inspire others by your chemistry vision!

Please feel free to start a scientific chemistry discussion here!

Discuss chemistry homework problems with experts!

Ask for help with chemical questions and help others with your chemistry knowledge!

Moderators: expert, ChenBeier, Xen

Post Reply
YukiCormyr
Newbie
Newbie
Posts: 1
Joined: Wed Feb 26, 2020 11:25 am

Van der Waals Equation - solve for n

Post by YukiCormyr »

I'm currently having trouble solving for n in the VdW gas equation for a calculator in excel for a variation of gases. I know there is a calculator on the site and I've tried my hand at doing the algebra, but I keep seeming to be just a touch off.

Is there anyone out there that has solved for n in this equation? If so, what is it???

Thanks!
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 493
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Post by ChenBeier »

p = nRT/(V - nb) -n^2 *a/V^2

p ( V - nb) = nRT - n^2*a*(V-nb)/V^2

pV^3 -pnbV^2 = nRTV^2 -n^2aV - n^3ab
n^3ab + n^2aV - nRTV^2- pnbV^2 + pV^3 = 0
n^3ab + n^2aV - n( RTV^2+pbV^2) + pV^3 = 0
n^3 + n^2*V/b - n( RTV^2+pV^2)/ab +pV^3/ab =0

This cubic equation is a type of

ax^3 + bx^2 + cx+ d = 0

This kind of questions have to be solved with tools of mathematics like curve discussion and differential equation, etc.
Post Reply