1. a. At what pressure does the first vapor bubble form? (in mmHg) b. What is it

Question

1. a. At what pressure does the first vapor bubble form? (in mmHg)

b. What is its composition? (mol benzene/mol)

2. a. At what pressure does the last droplet of liquid evaporate? (in mmHg)

b. What is its composition? (mol benzene/mol)

3. a. What are the liquid and vapor compositions in equilibrium with each other when the pressure is 800 mm Hg? (mol benzene/mol)

b. What is the ratio (mole vapor/mole liquid) at this point?

4. Estimate the volume of the cylinder contents when the pressure is 1300 mm Hg, 800 mm of Hg, and 600 mm Hg. (in L)

A mixture of 4.00 gram-moles of benzene and 6.00 gram-moles of toluene are placed in a closed cylinder equipped with a piston.

The cylinder is immersed in a bath of boiling water that maintains the temperature at 100.0°C.

The force exerted on the piston can be varied to adjust the cylinder pressure to any desired values.

The pressure is initially 1300 mm Hg and is gradually lowered to 600 mm Hg. Use the Pxy diagram below to convince yourself that the cylinder initially contains only liquid benzene and toluene and to answer the following questions.

1. a. At what pressure does the first vapor bubble form? (in mmHg)

b. What is its composition? (mol benzene/mol)

2. a. At what pressure does the last droplet of liquid evaporate? (in mmHg)

b. What is its composition? (mol benzene/mol)

3. a. What are the liquid and vapor compositions in equilibrium with each other when the pressure is 800 mm Hg? (mol benzene/mol)

b. What is the ratio (mole vapor/mole liquid) at this point?

4. Estimate the volume of the cylinder contents when the pressure is 1300 mm Hg, 800 mm of Hg, and 600 mm Hg. (in L)

115 110 105 G 100 95 90 85 80 75 70 65 1400 1300 1200 por 1100 JE 1000 900 800 a 700 600 500 0.2 0.4 0.6 0.8 1.0 Mole fraction benzene P 1 atm (a) Txy diagram 0.2 0.4 0.6 0.8 1.0 Mole fraction benzene T 100°C (b) Pry diagram

Explanation / Answer

1. a) At approximately 570 mmHg the first vapor bubble will form

b)The composition will be zero. Due to decrease in pressure the bubble will start to form hence the composition shows zero in graph.

2. a) At 1320mmHg pressure the last droplet of liquid will evaporate

b) the composition will be 1

3. a ) liquid composition will be 0. 3 and vapor composition will be 0. 5 at 800mmHg pressure.

b ) the ratio will be 0. 5/0. 3= 1. 67

4. Volume of cylinder contents

a ) for 1300mmHg

T = 373K P = 1300 R = 62. 36

p*v = nRT

n = nbenzene + ntoulene

   = 4/78. 11 +6/92. 14 ( mass of benzene and toulene is given )

   = 0. 1163

v= 0. 1163* 62. 36*373/1300=2. 08 L

For P = 600

v = 0. 1163*62. 36*373/600= 4. 51 L

for P =800

v = 0. 1163*62. 36*373/800=3. 38L

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