A volatile liquid A is placed in the tapered Stefan tube shown in Fig. P.11.4. The liquid evaporates and diffuses through the still air (B) in the tube until it reaches the top where it is dispersed in the atmosphere.

Assuming pseudo-steady state and that the mole fraction of A in the space above the air–liquid interface is a function only of the vertical distance from the interface:

(a) Develop an expression for the rate of evaporation of the liquid as a function of the height of liquid in the tube.

(b) Use your expression in

(a) to develop and expression that will predict how the liquid level will change as a function of time.

FIGURE P.11.4:

Transcribed Image Text:

Liquid, A Dt Do L 4