Question

Dry air near sea level has the following composition by volume: N2, 78.08 percent; O2, 20.94 percent; Ar, 0.93 percent; CO2, 0.05 percent. The atmospheric pressure is 1.00 atm. Calculate the concentration of each gas in moles per liter at 0°C?

Answer 1

`N_2 = 0.0348 (mol)/L`
`O_2 = 0.00934 (mol)/L`
`Ar = 0.00041 (mol)/L`
`CO_2 = 0.000022 (mol)/L`

Explanation:

The percentages do not change, so you really only need to calculate the total moles at the temperature and volume to find the ratios.

`PV = nRT` is the defining equation. We have 1.00atm pressure, 0'C (273'K) and 1 liter volume. The gas constant R for these dimensions is `0.0821 (L xx atm)/('K xx mol)`

`n = (PV)/(RT)` ; `n = (1 xx 1)/(0.0821 xx 273) = 0.0446` Total Moles/Liter.

`N_2 = 0.7808 xx 0.0446 = 0.0348 (mol)/L`
`O_2 = 0.2094 xx 0.0446 = 0.00934 (mol)/L`
`Ar = 0.0093 xx 0.0446 = 0.00041 (mol)/L`
`CO_2 = 0.0005 xx 0.0446 = 0.000022 (mol)/L`