Under steady-state equimolal counter-diffusion of two gases A and B, the value of NA/(NA + NB) is____________?
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Answer: B. ∞
Explanation
Equimolal counter-diffusion means that molar fluxes of gases A and B are equal magnitude opposites. Adding equal and opposite fluxes together results in a net zero denominator value. Dividing a finite flux by a vanishing sum drives the mathematical ratio towards infinity. Equimolar counter-diffusion occurs commonly in distillation columns where vapors and liquids exchange. Molar fluxes are defined as moles transferred per unit time and cross-sectional area. Steady-state conditions require that concentration profiles remain invariant with respect to time.
Fractional distillation column design calculations often assume equimolar counter-diffusion of components. This mechanism simplifies Stefan-Maxwell equations for binary ideal gas mixture separations. Understanding diffusion types helps engineers select appropriate mass transfer calculation models. A value of one represents stagnant film diffusion where one component has zero flux. A value of half implies unequal fluxes where one component dominates the transfer rate. Integer values like two represent specific stoichiometric flux ratios in reactive diffusion.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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