[sickness]

given CO₂ of 4200ppm or 4200mg/L
Atomic mass of about 44g for CO₂
making 4200 mg/L to 9.5*10^-2 mol/L
using P=(nRT/L) I get

9.5*10^-2*R*293.15 = 236.6

Question is what is the unit that I get on the 236.6 and if it is not atm is there a simple conversion for getting to atm

[jdurg]

Okay, right here you're using the ideal gas law which is PV=nRT.  They have given you the CO₂ value as 4200 mg/L.  So in one Liter you have 0.095 moles which you have correctly figured out.  So right now everything is good.  For your pressure, you can rearrange the ideal gas law to P=RT(n/L) which you have already done.  So your calculations are fine.  What you don't have right there is R.  R is a constant value that does not change.  It is something that you have to look up.  When you look up the value of R, you will find it as R=SomeNumber (Pressure Unit*VolumeUnit)/(TemperatureUnit*mole).  So if you want your units to be in atmospheres, you need to find the value of R which is for use with atmospheres.  

[sickness]

the R constant I get is 8.314 J/mol*Kg
Does this work?  This is what I used for the calculation
Is there another R value that gives me atm?  

[jdurg]

You are using the thermodynamic version of R.  You need to find the one that is used in the ideal gas law.  

[sickness]

This 8.314472 is what I get as the R in PV = nRT from my geochemistry book and many sources online so if you know something I do not and know a better number to use this would be most appreciated.

If there is not another number I have tried canceling the units and simplifying them and I am confused as to what it is.  My partner on this project is convinced that it is giving us pascals and if I just knew for sure the unit I am sure I could get the proper conversion.

Again thx

[Mitch]

Click the link in our menu to the left called Miscellaneous under the General: category. You'll find several different values for the gas constant.