Question 1

Which of the following statements best explains why iodine (I₂) is a solid at room temperature while chlorine (Cl₂) is a gas, despite both being nonpolar molecules?

Accepted Answer

Iodine has stronger London dispersion forces due to its larger number of electrons and greater polarizability.

Question 2

Which property is most directly related to the strength of intermolecular forces in a liquid?

Accepted Answer

Boiling point

Question 3

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

Accepted Answer

H₂O

Question 4

A sample of water is heated from -10\,^{\circ}\mathrm{C} to 110\,^{\circ}\mathrm{C}. Which equation would you use to calculate the energy required to melt the ice at 0\,^{\circ}\mathrm{C}?

Accepted Answer

$$\Delta H = n \Delta H_{\mathrm{fus}}$$

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 act between molecules.

Question 6

Which of the following substances will have the highest boiling point?

Accepted Answer

HF

Question 7

Which of the following is true about the viscosity of a liquid?

Accepted Answer

Viscosity increases as intermolecular forces become stronger.

Question 8

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 9

A phase diagram for water shows a negative slope for the solid–liquid equilibrium line. What does this indicate?

Accepted Answer

The melting point of ice decreases as pressure increases.

Question 10

Which of the following best explains why n-pentane (C₅H₁₂) has a higher boiling point than neopentane (C₅H₁₂)?

Accepted Answer

n-Pentane has a greater surface area, leading to stronger London dispersion forces.

Question 11

Which of the following statements about vapor pressure is correct?

Accepted Answer

Vapor pressure increases as temperature increases.

Question 12

Which of the following best describes the forces responsible for the dissolution of NaCl in water?

Accepted Answer

Ion–dipole interactions between Na⁺/Cl⁻ ions and water molecules

Question 13

Which of the following is NOT a property of gases as compared to liquids and solids?

Accepted Answer

Gases are virtually incompressible.

Question 14

Which of the following molecules is nonpolar and only exhibits London dispersion forces?

Accepted Answer

CCl₄

Question 15

Which equation would you use to calculate the energy required to heat a sample of liquid water (no phase change) from 20\,^{\circ}\mathrm{C} to 80\,^{\circ}\mathrm{C}?

Accepted Answer

$$\Delta H = m C_s \Delta T$$

Question 16

Which of the following best explains why water has an unusually high boiling point compared to other Group 6A hydrides?

Accepted Answer

Water forms strong hydrogen bonds due to the high electronegativity of oxygen.

Question 17

Which of the following phase changes requires the greatest input of energy per mole?

Accepted Answer

Vaporization

Question 18

Which of the following best describes capillary action in water?

Accepted Answer

Adhesive forces between water and glass are stronger than cohesive forces between water molecules.

Question 19

Which of the following statements about phase diagrams is correct?

Accepted Answer

The triple point is where all three phases (solid, liquid, gas) are in equilibrium.

Liquids and Intermolecular Forces: States of Matter and Phase Changes

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