Question 1

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

Accepted Answer

Ice has a lower density than liquid water due to the hydrogen bonding network that spaces molecules farther apart.

Question 2

Which intermolecular force is primarily responsible for the high boiling point of water compared to other group 16 hydrides?

Accepted Answer

Hydrogen bonding

Question 3

A sample of water is heated from −10 °C to 110 °C at 1 atm. Which equation would you use to calculate the heat required to melt the ice at 0 °C?

Accepted Answer

$$q = n \Delta H_{fus}$$

Question 4

Which of the following substances would you expect to have the highest boiling point?

Accepted Answer

CH$$_3OH$$

Question 5

A sealed flask contains liquid water and water vapor at equilibrium. If the temperature is increased, what happens to the vapor pressure?

Accepted Answer

Vapor pressure increases because more molecules have enough energy to escape into the gas phase.

Question 6

Which of the following best describes the process of sublimation?

Accepted Answer

A solid transitions directly to a gas without passing through the liquid phase.

Question 7

Which equation would you use to calculate the amount of heat required to vaporize 2.58 kg of water at its boiling point? (Molar mass of water = 18.02 g/mol, $$\Delta H_{vap} = 40.7 kJ/$$mol)

Accepted Answer

$$q = n \Delta H_{vap}$$

Question 8

Which of the following statements about surface tension is correct?

Accepted Answer

Surface tension is higher in liquids with stronger intermolecular forces.

Question 9

Which of the following best explains why oil and water do not mix?

Accepted Answer

Oil is nonpolar and water is polar, so their intermolecular forces are not compatible.

Question 10

Which of the following is true about the phase diagram of water?

Accepted Answer

The solid-liquid equilibrium line has a negative slope, indicating that ice is less dense than liquid water.

Question 11

Which of the following best describes the effect of increasing the surface area of a liquid at constant temperature on its vapor pressure?

Accepted Answer

Vapor pressure remains the same because it depends only on temperature.

Question 12

A 100 mL sample of water is placed in two different beakers: one with a diameter of 5 cm at 25 °C and one with a diameter of 7 cm at 55 °C. Which sample will have the greatest rate of vaporization?

Accepted Answer

The sample at 55 °C in the 7 cm diameter beaker.

Question 13

Which of the following best describes the relationship between the strength of intermolecular forces and the viscosity of a liquid?

Accepted Answer

Stronger intermolecular forces result in higher viscosity.

Question 14

Which of the following molecules can form hydrogen bonds?

Accepted Answer

HF

Question 15

Which of the following best describes the process occurring at the triple point in a phase diagram?

Accepted Answer

All three phases (solid, liquid, gas) are in equilibrium.

Question 16

Which of the following best explains why the heat of vaporization is much greater than the heat of fusion for water?

Accepted Answer

Vaporization requires complete separation of molecules, while fusion only requires partial disruption of intermolecular forces.

Question 17

Which of the following best describes the effect of adding salt to ice on the melting point of ice?

Accepted Answer

The melting point decreases because the salt disrupts the hydrogen bonding network.

Question 18

Which of the following equations correctly relates the vapor pressures and temperatures of a liquid at two different points using the Clausius-Clapeyron equation?

Accepted Answer

$$\ln \frac{P_2$}{P_1$} = -\frac{\Delta H_{vap}}{R} \left( \frac{1}{T_2$} - \frac{1}{T_1$} \right)$$

Question 19

A substance has a triple point at −24.5 °C and 225 mmHg. What will happen to a solid sample as it is warmed from −35 °C to 0 °C at a pressure of 220 mmHg?

Accepted Answer

The solid will sublime into a gas.

Question 20

Which of the following best explains why coastal cities experience smaller temperature fluctuations than inland cities?

Accepted Answer

Water has a high specific heat capacity, absorbing and releasing heat slowly.

Liquids, Solids, and Intermolecular Forces: Structure, Properties, and Phase Changes

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