Q: A sample of water at 100 $$^\\circC $$absorbs 122.1 kJ of heat. How many grams of water are vaporized? (Heat of vaporization of water at 100 $$^\\circC is 40.7 kJ/$$mol, molar mass of water = 18.02 g/mol)

$$122.1 \\text{ kJ} \\times \\frac{1 \\text{ mol}}{40.7 \\text{ kJ}} \\times \\frac{18.02 \\text{ g}}{1 \\text{ mol}} = 54.0 \\text{ g}$$

Q: A 50.0 g sample of ice at 0 $$^\\circC $$absorbs 167 kJ of heat. How much of the ice melts? (Heat of fusion for water = 6.02 kJ/mol, molar mass of water = 18.02 g/mol)

$$167 \\text{ kJ} \\times \\frac{1 \\text{ mol}}{6.02 \\text{ kJ}} \\times \\frac{18.02 \\text{ g}}{1 \\text{ mol}} = 500 \\text{ g}$$

Question 1

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

Accepted Answer

Water molecules are held together by hydrogen bonds, which are much stronger than the dispersion forces present in methane.

Question 2

A sample of water at 100 $$^\circC $$absorbs 122.1 kJ of heat. How many grams of water are vaporized? (Heat of vaporization of water at 100 $$^\circC is 40.7 kJ/$$mol, molar mass of water = 18.02 g/mol)

Accepted Answer

$$122.1 \text{ kJ} \times \frac{1 \text{ mol}}{40.7 \text{ kJ}} \times \frac{18.02 \text{ g}}{1 \text{ mol}} = 54.0 \text{ g}$$

Question 3

Which of the following statements about surface tension is correct?

Accepted Answer

Surface tension is caused by intermolecular forces that pull surface molecules toward the interior, minimizing surface area.

Question 4

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

Accepted Answer

A liquid with long-chain molecules and strong intermolecular forces.

Question 5

Which process is exothermic?

Accepted Answer

Condensation of steam to liquid water.

Question 6

A 50.0 g sample of ice at 0 $$^\circC $$absorbs 167 kJ of heat. How much of the ice melts? (Heat of fusion for water = 6.02 kJ/mol, molar mass of water = 18.02 g/mol)

Accepted Answer

$$167 \text{ kJ} \times \frac{1 \text{ mol}}{6.02 \text{ kJ}} \times \frac{18.02 \text{ g}}{1 \text{ mol}} = 500 \text{ g}$$

Question 7

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

Accepted Answer

Ice is less dense than liquid water because water expands upon freezing.

Question 8

Which of the following substances would you expect to have only dispersion forces as its primary intermolecular force?

Accepted Answer

Solid xenon (Xe)

Question 9

Which of the following is a correct statement about the boiling point of a liquid?

Accepted Answer

The boiling point is the temperature at which the vapor pressure of the liquid equals the external pressure.

Question 10

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 11

Which of the following is NOT a property of gases?

Accepted Answer

Definite volume

Question 12

Which type of crystalline solid is table salt (NaCl)?

Accepted Answer

Ionic solid

Question 13

Which of the following intermolecular forces is present in all substances, regardless of their composition?

Accepted Answer

Dispersion forces

Question 14

Which of the following best describes the process of sublimation?

Accepted Answer

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

Question 15

Which of the following is a manifestation of intermolecular forces in liquids?

Accepted Answer

Surface tension and viscosity

Question 16

Which of the following molecules can form hydrogen bonds?

Accepted Answer

NH$$_3$$

Question 17

Which of the following best describes the role of hydrogen bonding in DNA?

Accepted Answer

Hydrogen bonds hold complementary base pairs together, allowing DNA to replicate accurately.

Question 18

Which of the following statements about the energetics of melting and freezing is correct?

Accepted Answer

Melting is endothermic and freezing is exothermic.

Question 19

Which of the following best explains why the temperature of boiling water does not rise above 100 $$^ circC at 1 $$atm pressure, even if more heat is added?

Accepted Answer

The added heat is used to convert liquid water to steam, not to increase temperature.

Question 20

Which of the following is the strongest type of intermolecular force?

Accepted Answer

Ion-dipole force

Liquids, Solids, and Intermolecular Forces: Study Notes

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