Ideal gas law constant R conversion

sitinduk

Hi, not sure if this is the right forum to ask this in, but I was trying to convert the ideal gas law constant R (from PV = nRT) from:

8.31 (Pa * cu. meters) / (mol * Kelvin) to the equivalent:

10.73 (psia * cu. ft) / (lb. * mol * Rankine)

Here's the conversion factors I've been using:
1 Pa = 1.4505E-7 psia (absolute pressure)
1 cu. meter = 35.315 cu. ft
1 Rankine = 1.8 Kelvin

What I don't understand is where does the extra pounds in the denominator of the 10.73 value come from? This is probably what's throwing off my calculations.

-Thanks

Doc Al

In the first equation "mole" means "gram-Mole"; in the second the unit is "lb-Mole". You need to convert between gm-Moles and lb-Moles.

sitinduk

Ahh, using 1 gram = 0.0022 lb I finally got it. Thanks alot, this has really been bugging me

MiGUi

I always use this
[tex]R = 0.082 \frac{atm \cdot l}{mol \cdot K} = 2 \frac{cal}{mol \cdot K} = 8.314 \frac{J}{mol \cdot K} [/tex]

evert

Take a look at:
PDAcalc units This program runs on a palm, PocketPC,windows and will do all the conversions AUTOMATICALLY for you. Download the user manual which has an example of the PV = nRT formula that shows how it automatically convert between the different units.