Question

Orsat analysis of a stack gas on a dry basis is: \(\mathrm{N_2}=65%\), \(\mathrm{CO_2}=15%\), \(\mathrm{CO}=10%\), \(\mathrm{O_2}=10%\). The measured mole fraction of \(\mathrm{H_2O}\) in the stack gas (wet basis) is \(0.07\). The mole fraction of \(\mathrm{N_2}\) on a wet basis is ____________ (rounded off to two decimal places).

Hint:

Convert from dry to wet basis by multiplying dry-basis fractions by \((1-y_{H_2O})\).
Orsat analysis is always reported on a dry basis (water removed before analysis).

Answer 1

Correct Answer: 0.59

Step 1: On a wet basis, the water mole fraction is \(y_{H_2O}=0.07\).
Hence the dry-gas fraction in the wet mixture is \(1-y_{H_2O}=0.93\). Step 2: The dry-basis mole fraction of \(\mathrm{N_2}\) is \(x_{N_2,\text{dry}}=0.65\).
Therefore the wet-basis mole fraction is \[ y_{N_2}=x_{N_2,\text{dry}}\,(1-y_{H_2O}) =0.65\times 0.93=0.6045\approx \boxed{0.60}. \]