physical chemistry interpreting a phase diagram help me with

physical chemistry

interpreting a phase diagram

help me with self test 5c.8

Solution

Answer :

When heated it boils at 298 K (a2) giving a vapour of composition xB = 0.66 (b3). This product is near to the X_B = 0.4.The liquid gets richer in B, and the last drop (of pure B) evaporates at 390 K. The boiling range of the liquid is therefore 350 to 390 K.

If the initial vapour is drawn off, it has a composition xB = 0.4 but at temperature of 298 K. This composition would be maintained if the sample were very large, but for a finite sample it shifts to higher values and ultimately to xB = 0.95. This procce is end at this position.

Cooling the distillate corresponds to moving down the xB = 0.66 isopleth. At 330 K, for instance, the liquid phase has composition xB = 0.87, the vapour xB = 0.49; their relative proportions are 1:3. At 320 K the sample consists of three phases: the vapour and two liquids. One liquid phase has composition xB = 0.30; the other has composition xB = 0.80 in the ratio 0.62:1. Further cooling moves the system into the two-phase region, and at 298 K the compositions are 0.20 and 0.90 in the ratio 0.82:1. As further distillate boils over, the overall composition of the distillate becomes richer in B. When the last drop has been condensed the phase composition is the same as at the beginning.

At xB = 0.4 and temperature T = 298 K is the position between the line b3\' - b3\" and x axis. This is the lower phase of the phase diagram. This is the lower temperature of this phase diagram. All the points and composition is exist abobe this point and at higher temperature.