Question 1

Which of the following statements best explains why water (H$_2$O) has a much higher boiling point than hydrogen sulfide (H$_2$S), even though both are group 16 hydrides?

Accepted Answer

Water forms hydrogen bonds due to the presence of highly electronegative oxygen bonded to hydrogen, which are much stronger than the dipole-dipole forces in H$_2$S.

Question 2

Which type of intermolecular force is primarily responsible for the solubility of NaCl in water?

Accepted Answer

Ion-dipole forces

Question 3

A sample of diethyl ether has a vapor pressure of 401 mmHg at 15$^	ext{o}$C. If its molar heat of vaporization is 26 kJ/mol, what is its vapor pressure at 32$^	ext{o}$C? (Use $R = 8.314$ J/mol·K)

Accepted Answer

$P_2 \approx 1000$ mmHg

Question 4

Which of the following molecules can form hydrogen bonds with itself in the liquid state?

Accepted Answer

CH$_3$OH

Question 5

Which of the following best describes the difference between intramolecular and intermolecular forces?

Accepted Answer

Intramolecular forces hold atoms together within a molecule, while intermolecular forces are attractions between molecules.

Question 6

Which of the following factors does NOT increase the strength of London dispersion forces in a molecule?

Accepted Answer

Decreasing the number of atoms in the molecule

Question 7

A liquid rises in a narrow glass tube due to capillary action. Which statement best explains this phenomenon?

Accepted Answer

The adhesive forces between the liquid and the glass are stronger than the cohesive forces within the liquid.

Question 8

Which of the following substances would you expect to have the highest viscosity at room temperature?

Accepted Answer

Glycerol (C$_3$H$_8$O$_3$)

Question 9

Which of the following best describes what happens at the molecular level when a liquid reaches its boiling point?

Accepted Answer

The vapor pressure of the liquid equals the external atmospheric pressure.

Question 10

A phase diagram for water shows a triple point at 0.0098°C and 4.58 torr. What does the triple point represent?

Accepted Answer

The temperature and pressure at which solid, liquid, and vapor phases coexist in equilibrium.

Question 11

Which of the following best explains why iodine (I$_2$) is a solid at room temperature while chlorine (Cl$_2$) is a gas?

Accepted Answer

Iodine has stronger London dispersion forces due to its larger number of electrons and higher molar mass.

Question 12

Which of the following unit cells contains the greatest number of atoms per unit cell?

Accepted Answer

Face-centered cubic

Question 13

A metal crystallizes in a face-centered cubic (fcc) structure with an edge length $a$. What is the relationship between the atomic radius $r$ and the edge length $a$?

Accepted Answer

$a = 2\sqrt{2}r$

Question 14

Which of the following best describes the structure and bonding in metallic crystals?

Accepted Answer

Atoms are held together by delocalized electrons that move freely throughout the crystal.

Question 15

Which of the following is a property of amorphous solids such as glass?

Accepted Answer

They lack long-range order in the arrangement of their atoms.

Question 16

Which of the following best explains why the boiling point of 1,2,3-propanetriol (glycerol) is much higher than that of 1-propanol?

Accepted Answer

Glycerol has more –OH groups, allowing for more extensive hydrogen bonding.

Question 17

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 18

Which of the following is the correct Clausius–Clapeyron equation for relating vapor pressure and temperature?

Accepted Answer

$\ln P = -\frac{\Delta H_{	ext{vap}}}{R} \cdot \frac{1}{T} + C$

Question 19

Which of the following best explains why snowflakes have a six-sided symmetry?

Accepted Answer

The arrangement of water molecules in ice forms a hexagonal lattice due to hydrogen bonding.

Intermolecular Forces and the Physical Properties of Liquids and Solids

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