Question 1

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

Accepted Answer

Ice has a lower density than liquid water because its molecules form an open hexagonal structure stabilized by hydrogen bonds.

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

Which of the following statements about dispersion forces is CORRECT?

Accepted Answer

Dispersion forces are present in all atoms and molecules and increase with molecular size and surface area.

Question 4

Which molecule would you expect to have the highest boiling point: $$\mathrm{C_2H_6} ($$ethane), $$\mathrm{CH_2O} ($$formaldehyde), or $$\mathrm{CH_3OH} ($$methanol)?

Accepted Answer

$$\mathrm{CH_3OH}$$, due to hydrogen bonding

Question 5

Which of the following best describes why nonpolar substances like oil do not dissolve in water?

Accepted Answer

Nonpolar substances cannot form hydrogen bonds or strong dipole–dipole interactions with water.

Question 6

Which of the following liquids would you expect to have the highest surface tension at room temperature?

Accepted Answer

Water ($$\mathrm{H_2O})$$

Question 7

A sample of $$\mathrm{n}-$$pentane and a sample of neopentane both have the same molar mass. Why does $$\mathrm{n}-$$pentane have a higher boiling point?

Accepted Answer

$$\mathrm{n}-$$Pentane has a larger surface area for intermolecular interactions, leading to stronger dispersion forces.

Question 8

Which of the following best explains why vapor pressure increases with temperature?

Accepted Answer

More molecules have enough kinetic energy to escape the liquid phase as temperature increases.

Question 9

Which of the following substances would you expect to have the lowest viscosity at 20°C?

Accepted Answer

Benzene ($$\mathrm{C_6H_6})$$

Question 10

Which of the following best describes the process of sublimation?

Accepted Answer

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

Question 11

Which of the following statements about phase diagrams is CORRECT?

Accepted Answer

The triple point is where solid, liquid, and gas phases coexist in equilibrium.

Question 12

Which of the following best explains why water is a liquid at room temperature while similar-sized molecules like $$\mathrm{NH_3$}$$ and $$\mathrm{CH_4$}$$ are gases?

Accepted Answer

Water forms strong hydrogen bonds between molecules.

Question 13

Which of the following best describes the ion–dipole force?

Accepted Answer

It is the attraction between an ion and the partial charges on a polar molecule.

Question 14

A liquid boils when:

Accepted Answer

Its vapor pressure equals the external atmospheric pressure.

Question 15

Which of the following would increase the rate of vaporization of a liquid?

Accepted Answer

Decreasing the strength of intermolecular forces

Question 16

Which of the following best explains why capillary action occurs in a thin glass tube placed in water?

Accepted Answer

Adhesive forces between water and glass pull water up the tube, and cohesive forces pull more water along.

Question 17

Which of the following best describes the effect of increasing temperature on the surface tension of a liquid?

Accepted Answer

Surface tension decreases because increased molecular motion disrupts intermolecular forces.

Question 18

Which of the following is the strongest type of intermolecular force present in a mixture of sodium chloride ($$\mathrm{NaCl}) $$and water?

Accepted Answer

Ion–dipole force

Question 19

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 20

Which of the following best explains why the boiling point of $$\mathrm{I_2$} is $$higher than that of $$\mathrm{Cl_2$}$$?

Accepted Answer

$$\mathrm{I_2$}$$ has a larger molar mass, leading to stronger dispersion forces.

Liquids, Solids, and Intermolecular Forces: Structure, Properties, and Applications

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