Question

Referring to the table that follows,

Gas Composition (% by volume) of Air

N2 78.03

O2 20.99

Ar 0.94

CO2 0.033

Ne 0.0015

He 0.000524

Kr 0.00014

Xe 0.000006

a) Calculate the mol fraction of CO2

(b) Calculate the parts per million (ppm) by volume of CO2.

Answer 1

If this is composition by volume, then assume T is the same for all, so we can apply Avogrados law; which relates volume to moles

therefore...

% of CO2 = 0.033; then volume fraction is acutally = 0.033/100 = 0.00033

mol fraction = volume fraction

so

mol fraction = 0.00033

b)

ppm is given by = microL of CO2 / L of gas

assume a basis of 1 liter of gas

0.00033*1 = 0.00033 liters of CO2 = 0.00033*10^6 mL of CO2 = 330 microL

recalculate ppm;:

ppm = 330 mcroiL / L = 330 ppm of CO2