Confusion with the gas constant

[leaf345]

For the ideal gas law and van der waals eq'n, R can be a) 8.3145J/(k*mol) or b) 0.082058(L*atm)/(k*mol) . But if I use the first value of R, and try to solve for P my value always comes out as about 1000 smaller than it should be in Pa(ie/ it should be 2000 but it gives me 2). If I use the 2nd value, my value comes out in atm which is okay. But I can't use this value in another eq'n I need, so I don't want to use it. Is the ideal gas law supposed to be in kPa?

 

[cheechnchong]

For the ideal gas law and van der waals eq'n, R can be a) 8.3145J/(k*mol) or b) 0.082058(L*atm)/(k*mol) . But if I use the first value of R, and try to solve for P my value always comes out as about 1000 smaller than it should be in Pa(ie/ it should be 2000 but it gives me 2). If I use the 2nd value, my value comes out in atm which is okay. But I can't use this value in another eq'n I need, so I don't want to use it. Is the ideal gas law supposed to be in kPa?

hey,

i think since the gas constant is being used to calculate pressure...it should be the .082058(L*atm)/(k*mol)

the other one is for thermodynamics...it's units include the energy (J)

correct me if I am wrong

 

[gradeaswimr]

gas constants

the gas constant is either 0.08206L*atm/(K*mol) or 8.314L*kPa/(K*mol)

you should be able to use either or. i personally like to use kPa, but if you want to use atm, you could always convert from atm to kPa and the other way around using the equality 1atm = 101.3kPa.

 

[cheechnchong]

the gas constant is either 0.08206L*atm/(K*mol) or 8.314L*kPa/(K*mol)

you should be able to use either or. i personally like to use kPa, but if you want to use atm, you could always convert from atm to kPa and the other way around using the equality 1atm = 101.3kPa.

i disagree because one gas constant is used for thermo problems (heat and energy) and the other is for pressure probs...There is a definite difference between the two numbers

 

[Bystander]

i disagree because one gas constant is used for thermo problems (heat and energy) and the other is for pressure probs...There is a definite difference between the two numbers

WRONG! Units of the gas constant are energy per amount of substance per unit temperature; pressure x volume = energy. So long as one is consistent with units throughout a problem, one gets the "same" answer regardless of "which" gas constant one uses.

 

[cheechnchong]

WRONG! Units of the gas constant are energy per amount of substance per unit temperature; pressure x volume = energy. So long as one is consistent with units throughout a problem, one gets the "same" answer regardless of "which" gas constant one uses.

well, yeah that's what i meant when i posted previous response...I was definitely implying units of measurements!--if they give a pressure (atm, kpa, etc) or energy (J, kj...) keep consistent by using the appropriate gas constant

thinking back at my prev response...i can see it's sort of half wrong because i didnt set a stipulation for using a gas constant--my bad ...
they're not different because they're both gas constants
PS: i haven't had much experience with vander's law, but I've definitely plugged things into it...

 

[Borek]

0.08205783 L*atm/(K*mol)
8.314472 kPa*dm3/(K*mol)
8,314472 L*kPa/(K*mol)
8.314472 J/(mol*K)
62,3637 L*mmHg/(K*mol)
83,14472 L*mbar/(K*mol)
1.987216 cal/(K*mol)

or something

 

[Stevedye56]

0.08205783 L*atm/(K*mol)
8.314472 kPa*dm3/(K*mol)
8,314472 L*kPa/(K*mol)
8.314472 J/(mol*K)
62,3637 L*mmHg/(K*mol)
83,14472 L*mbar/(K*mol)
1.987216 cal/(K*mol)

or something

Borek
--
General Chemistry Software
www.pH-meter.info

pwned


or something...