Question 1

Which of the following best explains why water has a much higher boiling point than methane (CH$$_4$$), despite their similar molar masses?

Accepted Answer

Water molecules form hydrogen bonds, which are much stronger than the London dispersion forces present in methane.

Question 2

A gecko can climb smooth surfaces due to van der Waals forces. Which property of the gecko’s spatulae maximizes these forces?

Accepted Answer

The spatulae have a large surface area, increasing the magnitude of dispersion forces.

Question 3

Which of the following phase transitions is exothermic?

Accepted Answer

Condensation

Question 4

A sample of water is heated from $$-15\ ^\circ\mathrm{C} to$$ $$120\ ^\circ\mathrm{C}$$, passing through all phase changes. Which equation would you use to calculate the total heat required for the temperature changes (excluding phase changes)?

Accepted Answer

$$q = mC\Delta T$$ for each phase, then sum the values.

Question 5

Which of the following substances would you expect to have the highest viscosity at 25 $$^\circC$$?

Accepted Answer

Ethylene glycol ($$\mathrm{CH_2$(OH)CH_2$(OH)})$$

Question 6

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 7

Which of the following statements about phase diagrams is correct?

Accepted Answer

The triple point is where the solid, liquid, and gas phases are all in equilibrium.

Question 8

Which of the following best explains why mercury forms a convex meniscus in a glass tube, while water forms a concave meniscus?

Accepted Answer

Water has stronger adhesive forces with glass than cohesive forces, while mercury’s cohesive forces are stronger than its adhesive forces.

Question 9

Which of the following molecules would you expect to have the lowest boiling point?

Accepted Answer

Propane ($$\mathrm{CH_3CH_2CH_3})$$

Question 10

Which equation would you use to estimate the enthalpy of vaporization ($$\Delta H_{vap}) $$from vapor pressure data at two temperatures?

Accepted Answer

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

Question 11

Which of the following best explains why ethylene glycol has a lower vapor pressure than water at the same temperature?

Accepted Answer

Ethylene glycol has stronger intermolecular forces due to more extensive hydrogen bonding and larger molecular size.

Question 12

A liquid rises higher in a capillary tube with a smaller diameter. Which factor is primarily responsible for this phenomenon?

Accepted Answer

The adhesive forces between the liquid and the tube are stronger in narrower tubes, and the weight of the liquid column is less.

Question 13

Which of the following is a real-life application of supercritical fluids, as discussed in the study materials?

Accepted Answer

Supercritical carbon dioxide is used to decaffeinate coffee beans.

Question 14

Which of the following best describes the relationship between temperature and vapor pressure for a liquid?

Accepted Answer

As temperature increases, vapor pressure increases exponentially.

Question 15

Which of the following is NOT a van der Waals force?

Accepted Answer

Covalent bond

Question 16

Which of the following statements about hydrogen bonding in DNA is correct?

Accepted Answer

Hydrogen bonds form between complementary nitrogenous bases, stabilizing the double helix.

Question 17

Which of the following best explains why the boiling points of Group 16 hydrides (e.g., H$$_2O$$, H$$_2S$$, H$$_2Se) do $$not increase smoothly with increasing molar mass?

Accepted Answer

Hydrogen bonding in H$$_2O $$causes its boiling point to be much higher than expected based on molar mass.

Question 18

Which of the following is the correct expression for the total heat required to convert ice at $$-15\ ^\circ\mathrm{C} to $$steam at $$120\ ^\circ\mathrm{C}$$?

Accepted Answer

$$q_{total} = (mC\Delta T)_{ice} + n\Delta H_{fus} + (mC\Delta T)_{water} + n\Delta H_{vap} + (mC\Delta T)_{steam}$$

Liquids, Solids, and Intermolecular Forces: General Chemistry Study Guide

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