Questions (15)-(18) refer to this temperature-composition phase diagram shown be

Question

Questions (15)-(18) refer to this temperature-composition phase diagram shown below 15.) If you mix A and B with a composition of 0.2 at temperature 140 C, you get a Single liquid phase Single-vapor phase d) None of the above 16.) The boiling point of a liquid with x,-0.15 is (c.) Two phases: liquid and vapor approximately (use the phase diagram shown above) (a.) 120 (b.) 130 (c.) 136 (d.) 140 17.) Use the phase diagram shown above to estiate the composition of the vapor phase y, when the liquid just starts to boil, (a.) 0.35 (b.) 0.25 (c.) 0.15 (d.) 0.45 18.) If you want to use fractional distillation to separate A from B, and you want the final mole fraction of A to be 0.9, what is the minimum number of theoretical plates that are required? (a.) 2 (b.) 3 (c.) 4 (d.) 5

Explanation / Answer

1) Single Vapor Phase

Take x-axis coordinate ZA = 0.2 and draw verticle line and draw a horizontal line from T = 140oC. The point of intersection represents the phase at that point which comes out to be vapor phase.

2) 130oC

At xA = 0.15 draw a vertical line. The point where it will intersect the lower curve is the first point of boiling or first point of conversion of liquid to vapor. Draw a horizontal line which will intersect the y-axis at 130oC.

3) 0.35

Horizontal line drawn in above extends to the upper curve which makes it a tie line where both the phases exist. The other point on the upper cuver, draw a vertical line to the x-axis which will represent the vapor phase composition of A,i.e., yA = 0.35

4) 4

Draw steps from xA = 0.5 until you reaches the desired fraction , i.e., xA = 0.9. 4 Steps can be drawn which will represent the number of theoretical plates.

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