How do I Calculate Bulk Concentration?

[dancingenigma]

Hello,
I'm trying to calculate the bulk concentration of Oxygen in Air and Hydrogen in pure Hydrogen in mol cm-3.

I have looked on websites but couldn't find any answer.
Can anyone please help.

 

[25362]

I hope I understood your query.
Consider that 1 mol of an ideal gas at NTP occupies 22.4 L = 22,400 cm³.
NTP is taken at 0^oC and 101.3 kPa.

For oxygen at 21% vol in air [→] 0.21[÷]22,400 mol/cm³

For hydrogen at 100% vol [→] 1.0[÷]22,400 mol/cm³

 

[dancingenigma]

Thanks a lot for the reply.
I'm sorry for my ignorance in the subject but what does NTP stand for?

 

[djack77494]

NTP stands for "Normal Temperature and Pressure". You will also see STP fairly often in this business. It stands for "Standard Temperature and Pressure". Not to overly confuse the issue, but the "definition" of what is normal and what is standard can also vary, depending on the particular industry and depending on whether SI or FPS units are used.
Doug

 

[dancingenigma]

Thanks Doug,
The application will be running at 80 C the previously given figures for the bulk concentration were given at a NTP of 0, does this mean that the figures would change?
If so then how would I work it out?

 

[25362]

The volume of 1 mol of an ideal gas at 1 atm. abs. and 273 K, is computed as follows:

V = nRT/P = (1.0 mol)(8.314J/K.mol)(273 K)[÷]1.013 [×]10⁵ Pa​

= 22.4[×]10^-3 m³ = 22.4 L​

If the "new" conditions are 1 atm abs (101.3 kPa) and 80^oC, and applying the above ideal gas law, the "new" volume would be proportional to the "new" absolute temperature of (273+80=) 353 K.

The "new" volume would be: 22,400 [×] 353[÷]273 ~ 29,000 cm³/mol. This fact reduces the number of mols/cm³ accordingly.

Kindly note these molecular gases have been considered ideal. Changes in pressure and temperature removes them from ideality. To get their actual molar volumes at varying conditions you may use the following link:

http://webbook.nist.gov/chemistry/

After writing the gas name point to "fluid properties" and select m³/mol