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 :smile:

[MiGUi]

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

[evert]

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

Take a look at:
PDAcalc units (http://www.adacs.com/menu/PDAcalc_units.php) 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.