The Foundations of Chemistry

536 CHAPTER 13: Liquids and Solids

(b) Using the following vapor pressure data, plot ln Pvs.

1/Tfor ethyl acetate, CH 3 COOC 2 H 5 , a common organic

solvent used in nail polish removers.

t(°C) 43.4. 23.5. 13.5. 3.0. 
9.1.

vp (torr) 1. 5. 10. 20. 40.

t(°C) 16.6. 27.0. 42.0. 59.3.

vp (torr) 60. 100. 200. 400.

(c) From the plot, estimate Hvapfor ethyl acetate.

(d) From the plot, estimate the normal boiling point of

ethyl acetate.

0 *61.Repeat Exercise 60(b) and 60(c) for mercury, using the

following data for liquid mercury. Then compare this

value with the one in Appendix E.

t(°C) 126.2 184.0. 228.8. 261.7. 323.0.

vp (torr) 1 10. 40. 100. 400.

*062.Isopropyl alcohol, C 3 H 8 O, is marketed as “rubbing alco-

hol.” Its vapor pressure is 100. torr at 39.5°C and 400. torr

at 67.8°C. Estimate the molar heat of vaporization of iso-

propyl alcohol.

*063.Using data from Exercise 62, predict the normal boiling

point of isopropyl alcohol.

*064.Boiling mercury is often used in diffusion pumps to attain

a very high vacuum; pressures down to 10^10 atm can be

readily attained with such a system. Mercury vapor is very

toxic to inhale, however. The normal boiling point of liq-

uid mercury is 357°C. What would be the vapor pressure

of mercury at 25°C?

Phase Diagrams

*065.How many phases exist at a triple point? Describe what

would happen if a small amount of heat were added under

constant-volume conditions to a sample of water at the

triple point. Assume a negligible volume change during

fusion.

*066.What is the critical point? Will a substance always be a

liquid below the critical temperature? Why or why not?

Refer to the phase diagram of CO 2 in Figure 13-17b to answer

Exercises 67–70.

*067.What phase of CO 2 exists at 2 atm pressure and a tem-

perature of 90°C? 60°C? 0°C?

*068.What phases of CO 2 are present (a) at a temperature of

78°C and a pressure of 1 atm? (b) at 57°C and a pres-

sure of 5.2 atm?

*069.List the phases that would be observed if a sample of CO 2

at 8 atm pressure were heated from 80°C to 40°C.

*070.How does the melting point of CO 2 change with pres-

sure? What does this indicate about the relative density

of solid CO 2 versus liquid CO 2?

0 *71.You are given the following data for ethanol, C 2 H 5 OH.

Normal melting point 117°C

Normal boiling point 78.0°C

Critical temperature 243°C

Critical pressure 63.0 atm

Assume that the triple point is slightly lower in temper-

ature than the melting point and that the vapor pressure

at the triple point is about 10^5 torr. (a) Sketch a phase

diagram for ethanol. (b) Ethanol at 1 atm and 140.°C is

compressed to 70. atm. Are two phases present at any

time during this process? (c) Ethanol at 1 atm and 270.°C

is compressed to 70. atm. Are two phases present at any

time during this process?

0 *72.You are given the following data for butane, C 4 H 10.

Normal melting point 138°C

Normal boiling point 0°C

Critical temperature 152°C

Critical pressure 38 atm

Assume that the triple point is slightly lower in temper-

ature than the melting point and that the vapor pressure

at the triple point is 3 10 ^5 torr. (a) Sketch a phase dia-

gram for butane. (b) Butane at 1 atm and 140°C is

compressed to 40 atm. Are two phases present at any time

during this process? (c) Butane at 1 atm and 200°C is

compressed to 40 atm. Are two phases present at any time

during this process?

Temperature (°C)

Pressure (atm)

40 60 80 100 120 140 160 180 200

to F

Liquid

Rhombic

Vapor

Monoclinic

D G

C

E

B

10 –6 A

10 –5

10 –4

10 –3

10 –2

10 –1

1

101

102

103

104

Phase Diagram for Sulfur