Q: A 0.50 g sample of water at 100 °C is completely vaporized. How much heat (in kJ) is required? (Use $$\Delta H_{vap} = 40.7\ \mathrm{kJ/mol}$$, $$M_{H_2O} = 18.02\ \mathrm{g/mol})$$

$$0.50\ \mathrm{g} \times \frac{1\ \mathrm{mol}}{18.02\ \mathrm{g}} \times 40.7\ \mathrm{kJ/mol} = 1.13\ \mathrm{kJ}$$

Q: A 10.0 g ice cube at 0 °C is placed in 100 g of water at 25 °C. How much heat is absorbed by the ice as it melts? ($$\Delta H_{fus} = 6.02\ \mathrm{kJ/mol}$$, $$M_{H_2O} = 18.02\ \mathrm{g/mol})$$

$$10.0\ \mathrm{g} \times \frac{1\ \mathrm{mol}}{18.02\ \mathrm{g}} \times 6.02\ \mathrm{kJ/mol} = 3.34\ \mathrm{kJ}$$

Question 1

Which of the following best explains why water has a much higher boiling point than methane (CH4), despite their similar molar masses?

Accepted Answer

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

Question 2

A 0.50 g sample of water at 100 °C is completely vaporized. How much heat (in kJ) is required? (Use $$\Delta H_{vap} = 40.7\ \mathrm{kJ/mol}$$, $$M_{H_2O} = 18.02\ \mathrm{g/mol})$$

Accepted Answer

$$0.50\ \mathrm{g} 	imes \frac{1\ \mathrm{mol}}{18.02\ \mathrm{g}} 	imes 40.7\ \mathrm{kJ/mol} = 1.13\ \mathrm{kJ}$$

Question 3

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

Accepted Answer

Glycerol (C3H8O3), which forms extensive hydrogen bonds

Question 4

Which of the following statements about surface tension is correct?

Accepted Answer

Surface tension is higher in liquids with stronger intermolecular forces.

Question 5

A 10.0 g ice cube at 0 °C is placed in 100 g of water at 25 °C. How much heat is absorbed by the ice as it melts? ($$\Delta H_{fus} = 6.02\ \mathrm{kJ/mol}$$, $$M_{H_2O} = 18.02\ \mathrm{g/mol})$$

Accepted Answer

$$10.0\ \mathrm{g} 	imes \frac{1\ \mathrm{mol}}{18.02\ \mathrm{g}} 	imes 6.02\ \mathrm{kJ/mol} = 3.34\ \mathrm{kJ}$$

Question 6

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 7

Which of the following is NOT a type of crystalline solid?

Accepted Answer

Amorphous solid

Question 8

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

Accepted Answer

Ion–dipole force

Question 9

Which of the following statements about evaporation is FALSE?

Accepted Answer

Evaporation is exothermic because it releases heat to the surroundings.

Question 10

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

Accepted Answer

NH3

Question 11

Which of the following best explains why coastal cities tend to have milder winter temperatures than deserts?

Accepted Answer

Condensation of water vapor in the air releases heat, moderating temperature drops.

Question 12

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 13

Which of the following statements about dispersion forces is TRUE?

Accepted Answer

Dispersion forces are present in all atoms and molecules.

Question 14

Which of the following liquids would you expect to have the lowest vapor pressure at 25 °C?

Accepted Answer

Water ($$\Delta H_{vap} = 40.7\ \mathrm{kJ/mol})$$

Question 15

Which of the following is a correct statement about the heating curve of water?

Accepted Answer

During boiling, the temperature remains constant until all the liquid has vaporized.

Question 16

Which of the following best describes why oil and water do not mix?

Accepted Answer

Oil is nonpolar and water is polar, so their intermolecular forces are not compatible.

Question 17

Which of the following solids is held together primarily by covalent bonds?

Accepted Answer

Diamond (C)

Question 18

Which of the following is a real-life consequence of water’s expansion upon freezing?

Accepted Answer

Ice floats on lakes, insulating aquatic life below.

Question 19

Which of the following intermolecular forces is the strongest?

Accepted Answer

Ion–dipole force

Question 20

Which of the following best explains the specificity of base pairing in DNA?

Accepted Answer

Hydrogen bonds form only between specific pairs of bases (A with T, C with G).

Liquids, Solids, and Intermolecular Forces: Study Guide for Introductory Chemistry

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