Question

2.
a. The exhaust gases from a combustion engine consist of 90% (molar) of water vapor, 5% CO2, and
toxic gases - 2.5% CO, 2.4% NO and 0.1% ozone (O3). What is the average MW of the exhaust gases
in lbm/lbmole.
b. What is the ozone concentration in the exhaust gases in ppm?

Answer 1

Solution :

The exhaust gases from a combustion engine consist of 90% (molar) of water vapor, 5% CO2, and toxic gases - 2.5% CO, 2.4% NO and 0.1% ozone (O3).

Consider basis as exhaust gases as 100 mol,

So it contains 90 mol of H2O, 5 mol of CO2, 2.5 mol of CO, 2.4 mol of NO, and 0.1 mol of O3.

Average molecular weight Mw = total mass/total moles.

Mw = (90*18 + 5*44 + 2.5*28 + 2.4*30 + 0.1*48)/100

Mw = 19.868 gm/mol

Answer : a) Mw = 19.868 lbm/lbmol

Answer : b)

Ozone concentration Co3 = mass of ozone / total mass

Co3 = (0.1*48) / (19.868*100) * 10^6 ppm

Co3 = 2416 ppm