GATE 2023 CH – Question 35
In a binary gas-liquid system, $N_{A,EMD}$ is the molar flux of a gas $A$ for equimolar counter diffusion with a liquid $B$. $N_{A,UMD}$ is the molar flux of $A$ for steady one-component diffusion through stagnant $B$. Using the mole fraction of $A$ in the bulk of the gas phase as 0.2 and that at the gas-liquid interface as 0.1 for both the modes of diffusion, the ratio of $N_{A,UMD}$ to $N_{A,EMD}$ is equal to ______ (rounded off to two decimal places).
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Correct answer: 1.17 to 1.19
Explanation
For the same driving force, $N_{A,UMD} = N_{A,EMD} \times \frac{1}{(1 - y_A)_{lm}}$ where $(1 - y_A)_{lm} = \frac{0.9 - 0.8}{\ln(0.9/0.8)} = \frac{0.1}{0.11778} = 0.849$. So the ratio is $\frac{1}{0.849} = 1.18$.