Project ForgeAmmonia (component 1) is evaporating from a partially filled bottle into surrounding air (component 2). The liquid level and the concentration of ammonia at the top of the bottle are maintained constant. Ni is the molar flux relative to a fixed location and Ji is the molar flux with respect to the average molar velocity. Assume that air in the bottle is stagnant. Which ONE of the following is CORRECT?
- N1=constant, N2=0, J1+J2=0
- BN1+N2=0, J1+J2=0
- CN1+N2=0, J1=constant, J2=0
- DN1=constant, N2=0, J1=constant, J2=0
Explanation
This is classic Stefan diffusion through a stagnant film: air (component 2) does not move in bulk, N2=0, while ammonia diffuses steadily, N1=constant. The identity ΣJi=0 always holds for diffusive fluxes referenced to the molar-average velocity in a binary system, so J1+J2=0 regardless.
Source: GATE CH 2011 (2011)
This question is part of a 15-day revision cycle — sign in and Project Forge will bring it back the day before you'd forget it.