The mass flux equation NA = (DAB . Pt /RTZ . PBM) (PA1 – PA2) applies specifically to_______________________?
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Answer: B. Steady state diffusion for stagnant case
Explanation
The provided mass flux equation describes steady-state molecular diffusion of gas A through stagnant gas B. In this stagnant case, component B has zero net flux while component A diffuses through it. Log mean partial pressure terms of the stagnant component appear in the denominator of the flux expression. Fick's first law forms the foundational basis for deriving specific molecular diffusion flux equations. Steady state implies that concentration profiles do not change with respect to time within the diffusion path. Non-diffusing gas scenarios are common in industrial absorption and evaporation unit operations.
Chemical engineers use this Stefan diffusion equation to calculate evaporation rates of liquids into gases. Designing absorption columns requires accurate mass transfer flux models for gas-liquid interfaces. Understanding stagnant gas diffusion helps predict drying rates and pollutant dispersion in air. Fick's second law governs unsteady-state diffusion where concentration varies with both time and position. Liquid M.T.C. by Higbie penetration theory utilizes unsteady diffusion into liquid eddies, not this equation. None of these is incorrect because option B accurately identifies steady-state stagnant gas diffusion.
- Subject
- Engineering
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- Chemical Engineering
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- medium
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