Chapter 10: Liquids and Solids

Carbon tetrachloride, $\mathrm{C}\mathrm{C}{\mathrm{l}}_4$, was once used as a dry-cleaning solvent, but is no longer used because it is carcinogenic. At $\mathbf{57}.\mathbf{8}$°C, the vapor pressure of $\mathrm{C}\mathrm{C}{\mathrm{l}}_4$ is $\mathbf{54}.\mathbf{0}$kPa, and its enthalpy of vaporization is $\mathbf{33}.\mathbf{05}$kJ/mol. Use this information to estimate the normal boiling point for $\mathrm{C}\mathrm{C}{\mathrm{l}}_4$.

How does the boiling of a liquid differ from its evaporation?

Use the information to estimate the boiling point of water in Denver when the atmospheric pressure is $83.3$kPa

A syringe at a temperature of $20^{\mathrm{o}}\mathrm{C}$ is filled with liquid ether in such a way that there is no space for any vapour. If the temperature is kept constant and the plunger is withdrawn to create a volume that can be occupied by vapour, what would be the approximate pressure of the vapour produced?

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.

Explain why the molar enthalpies of vaporization of the following substances increase in the order $\mathrm{C}{\mathrm{H}}_4<{\mathrm{C}}_2{\mathrm{H}}_6<{\mathrm{C}}_3{\mathrm{H}}_8$, even though the type of IMF (dispersion) is the same.

Explain why the enthalpies of vaporization of the following substances increase in the order CH₄ < NH₃ < H₂O, even though all three substances have approximately the same molar mass.

The enthalpy of vaporization of $\mathrm{C}{\mathrm{O}}_2(\mathrm{l})$ is 9.8 kJ/mol. Would you expect the enthalpy of vaporization of $\mathrm{C}{\mathrm{S}}_2(\mathrm{l})$ to be 28 kJ/mol, 9.8 kJ/mol, or -8.4 kJ/mol? Discuss the plausibility of each of these answers.

The hydrogen fluoride molecule, HF, is more polar than a water molecule, ${\mathrm{H}}_2\mathrm{O}$ (for example, HF has a greater dipole moment). Yet the molar enthalpy of vaporization for liquid hydrogen fluoride is lesser than that of water. Explain.

Ethyl chloride 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.