10.3 Phase Transitions
Melting, boiling, and sublimation temperatures set by intermolecular attraction, with heat flows from enthalpies of fusion and vaporization.
12 exercises
10.3 Exercise 2
Heat is added to ice at 0 °C. Explain why the temperature of the ice does not change. What does change?
10.3 Exercise 4
Identify two common observations indicating some liquids have sufficient vapor pressures to noticeably evaporate?
10.3 Exercise 6
What is the relationship between the intermolecular forces in a liquid and its vapor pressure?
10.3 Exercise 8
Why does spilled gasoline evaporate more rapidly on a hot day than on a cold day?
10.3 Exercise 10
When is the boiling point of a liquid equal to its normal boiling point?
10.3 Exercise 12
Use the information in the figure to estimate the boiling point of water in Denver when the atmospheric pressure is 83.3 kPa.
10.3 Exercise 14
Explain the following observations:
(a) It takes longer to cook an egg in Ft. Davis, Texas (altitude, 5000 feet above sea level) than it does in Boston (at sea level).
(b) Perspiring is a mechanism for cooling the body.
10.3 Exercise 16
Explain why the molar enthalpies of vaporization of the following substances increase in the order CH4 < C2H6 < C3H8, even though the type of IMF (dispersion) is the same.
10.3 Exercise 18
The enthalpy of vaporization of CO2(l) is 9.8 kJ/mol. Would you expect the enthalpy of vaporization of CS2(l) to be 28 kJ/mol, 9.8 kJ/mol, or −8.4 kJ/mol? Discuss the plausibility of each of these answers.
10.3 Exercise 20
Ethyl chloride (boiling point, 13 °C) is used as a local anesthetic. When the liquid is sprayed on the skin, it cools the skin enough to freeze and numb it. Explain the cooling effect of liquid ethyl chloride.
10.3 Exercise 22
How much heat is required to convert 422 g of liquid H2O at 23.5 °C into steam at 150 °C?
10.3 Exercise 24
Titanium tetrachloride, TiCl4, has a melting point of −23.2 °C and has a ΔH fusion = 9.37 kJ/mol.
(a) How much energy is required to melt 263.1 g TiCl4?
(b) For TiCl4, which will likely have the larger magnitude: ΔH fusion or ΔH vaporization? Explain your reasoning.
Adapted from General Chemistry © 2019 Rice University. Licensed under CC BY 4.0. Sources: Chemistry 2e, Chemistry: Atoms First 2e. Imported at revision 32c7196.