Q: Which equation is used to relate the vapor pressure of a liquid to its temperature and enthalpy of vaporization?

$$\ln P = -\left(\frac{\Delta_\text{vap} H^\circ}{R}\right)\left(\frac{1}{T}\right) + C$$

Question 1

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Ice is less dense than liquid water due to the open lattice structure formed by hydrogen bonding.

Question 2

Which intermolecular force is primarily responsible for the high boiling point of water compared to other Group 6A hydrides?

Accepted Answer

Hydrogen bonding

Question 3

A sample of ethanol (C$$_2H$_6O) $$has a density of 0.7849 g/mL. If the enthalpy of vaporization is 42.32 kJ/mol, how much energy is required to vaporize 175 mL of ethanol at 25$$^	ext{o}C$$? (Molar mass = 46 g/mol)

Accepted Answer

$$121\ 	ext{kJ}$$

Question 4

Which of the following statements about intermolecular forces is correct?

Accepted Answer

Hydrogen bonds are a special type of dipole-dipole interaction and are not true chemical bonds.

Question 5

Which property of liquids is most directly affected by the strength of intermolecular forces?

Accepted Answer

Viscosity

Question 6

Which of the following best describes the process of vaporization?

Accepted Answer

It is an endothermic process where energy is absorbed to break intermolecular forces.

Question 7

Which equation is used to relate the vapor pressure of a liquid to its temperature and enthalpy of vaporization?

Accepted Answer

$$\ln P = -\left(\frac{\Delta_	ext{vap} H^\circ}{R}ight)\left(\frac{1}{T}ight) + C$$

Question 8

Which of the following substances would you expect to have the highest boiling point, based on intermolecular forces?

Accepted Answer

H$$_2O$$

Question 9

A phase diagram shows that the slope of the solid-liquid boundary for water is negative. What does this indicate?

Accepted Answer

The liquid phase is more dense than the solid phase.

Question 10

Which of the following best explains why NaCl has a much higher melting point than HCl?

Accepted Answer

NaCl is held together by strong ionic bonds, while HCl is held together by weaker dipole-dipole forces.

Question 11

Which of the following is a consequence of hydrogen bonding in water?

Accepted Answer

Water has a high specific heat capacity.

Question 12

Which intermolecular force is responsible for the solubility of O$$_2 in $$water?

Accepted Answer

Dipole-induced dipole forces

Question 13

A nonpolar molecule such as I$$_2$$ can dissolve in ethanol (CH$$_3CH$_2OH) $$because:

Accepted Answer

Ethanol induces a temporary dipole in I$$_2$$, leading to dipole-induced dipole interactions.

Question 14

Which of the following statements about viscosity is correct?

Accepted Answer

Liquids with strong intermolecular forces have higher viscosity.

Question 15

Which of the following is true about the normal boiling point of a liquid?

Accepted Answer

It is the temperature at which the vapor pressure equals 760 torr.

Question 16

Which of the following best describes a supercritical fluid?

Accepted Answer

It has the density of a liquid and the viscosity of a gas.

Question 17

Which of the following is the strongest type of intermolecular force present in a solution of NaCl dissolved in water?

Accepted Answer

Ion-dipole forces

Question 18

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 19

Which of the following factors increases the strength of London dispersion forces?

Accepted Answer

Increasing the number of electrons in the molecule

Question 20

Which of the following best explains why the boiling point of ICl is higher than that of Br$$_2$$?

Accepted Answer

ICl is polar and experiences dipole-dipole forces, while Br$$_2 is $$nonpolar and only experiences dispersion forces.

Liquids and Intermolecular Forces: Chapter 11 Study Guide

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