1.4b. Concentration of a flue gas.
A flue gas consists of carbon dioxide, oxygen, water vapor, and nitrogen. The molar fractions of CO2 and O2 in a sample of the gas are 12% and 6%, respectively. The weight fraction of H2O in the gas is 6.17%. Estimate the density of this gas at 500 K and 110 kPa.

Solution
Basis: 100 kmole of gas mixture

Let x = molar fraction of water in the mixture (as a percent)
Initial estimate
From the given water weight fraction (0.0617):