Posted by **terrence** on Wednesday, August 31, 2011 at 6:51am.

I'm having a problem with the gas constant. This is it:

In the question: Calculate the amount of moles of a gas if .455 occupies a volume of 250mL at 27 degrees Celsius and 772mmHg.

I do all the correct steps using the R = 8.314 for the 772mmHg. I get .077 for this, which is incorrect.

Then I do the same thing but convert the 772mmHg to 1.016atm and for the gas constant use .08206. I get .0103 which is the correct answer. Why does it make a difference which I used? In fact i tried using the larger constant with units of Pa in a question and didnt get it right, but did it again with the smaller constant in units atm and got it right. Please please help this confusion. Thanks

- chemistry -
**DrBob222**, Wednesday, August 31, 2011 at 7:09pm
R is 0.08206 with V in L and P in atm.

R is 8.314 with V in L and P in kPa.

By the way, I have no idea what the 0.455 is in your post and there are no units. I ignored it.

0.0103 is n either way.

n = (PV/RT) = (772 x 0.250)/(760 x 0.08206 x 300) = 0.0103 = n

772 x 101.325/760 = 102.92 kPa.

(102.92 x 0.250)/(8.314 x 300) = 0103 = n

## Answer This Question

## Related Questions

- Chemistry - 1. Calculate the number of molecules in a deep breath of air whose ...
- Chemistry 3A - a sample of methan gas, CH4, occupies 4.50L at a temp of 20.0 ...
- Chem hw! - 1. What pressure would be needed to compress 25.1 mL of hydrogen at 1...
- Chem hw! - 1. What pressure would be needed to compress 25.1 mL of hydrogen at 1...
- sciencee - 1. What pressure would be needed to compress 25.1 mL of hydrogen at 1...
- Chemistry - I'm having trouble trying to figure out how to setup and solve these...
- Chemistry - If a gas at 1.2 atm of pressure and 22.0 degrees of Celsius occupies...
- Chemistry - If a gas at 1.2 atm of pressure and 22.0 degrees of Celsius occupies...
- Chem II - A sample of gas at 38 degrees Celsius occupies a volume of 2.97 L and ...
- Chemistry 111 - A gas occupies a volume of 256mL at a pressure of 250torr at 32 ...

More Related Questions