Physics Forums

Physics Forums (http://www.physicsforums.com/index.php)
-   Introductory Physics Homework (http://www.physicsforums.com/forumdisplay.php?f=153)
-   -   Ideal Gas Law (http://www.physicsforums.com/showthread.php?t=578947)

JSGandora Feb18-12 01:41 PM

Ideal Gas Law
 
1. The problem statement, all variables and given/known data
What is the pressure inside a $50.0$ L container holding $105.0$ kg of argon gas at $20^\circ$ C?


2. Relevant equations
Ideal Gas Law: PV=nRT


3. The attempt at a solution
From the ideal gas law, I get
[itex]
P=\frac{nRT}{V}=\frac{\frac{105.0\times 10^3g}{36g/mol}\times 0.08214\frac{L\cdot atm}{mol\cdot K}\times 293^\circ K}{50.0 L}=25258atm
[/itex]
which seems much too large. Am I doing something wrong?

SpecialKM Feb18-12 01:52 PM

Re: Ideal Gas Law
 
Nope! Your answer is quite reasonable, and it seems like nothing looks wrong in your setup of P= nRT/V and all the units match, your value for R is correct and you've converted C to K. Unless you made a calculating mistake, everything looks correct to me.

JSGandora Feb18-12 01:57 PM

Re: Ideal Gas Law
 
Oh wow, thanks! It's hard to believe the massive pressure inside, which was why I was skeptical. Thanks again.

SpecialKM Feb18-12 02:04 PM

Re: Ideal Gas Law
 
On second glance, your molar mass for Argon seems to be off, also, you've made a calculation error. Try again and tell me what you got. (I've worked it out this time).

JSGandora Feb18-12 02:05 PM

Re: Ideal Gas Law
 
Oh, should it be [itex]39.95\times 2[/itex] since it's diatomic?

SpecialKM Feb18-12 02:07 PM

Re: Ideal Gas Law
 
Nono, on the work you've showed in your original post, it looks like you've put 36 g/mol.

JSGandora Feb18-12 02:14 PM

Re: Ideal Gas Law
 
But the molecular mass of Argon is 39.95 isn't it? I'm just substituting the 36 for 39.95x2.

SpecialKM Feb18-12 02:18 PM

Re: Ideal Gas Law
 
By looking at the problem you've presented it should look like this:

P = [(105000/39.95)(0.08214)(293)]/(50)
P = 1265.1 atm
P = 1.27 x 10^3 atm

I've left out the units for simplicity, but you should write them in yourself.

JSGandora Feb18-12 02:22 PM

Re: Ideal Gas Law
 
Oh, yeah. For some reason I thought argon was diatomic...


All times are GMT -5. The time now is 04:22 AM.

Powered by vBulletin Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
© 2014 Physics Forums