Q: Calculate the mass of water (in grams) that can be vaporized at its boiling point with 122.1 kJ of heat. The heat of vaporization of water at 100°C is $40.7\ \mathrm{kJ/mol}$ and the molar mass of water is $18.02\ \mathrm{g/mol}$.

$122.1\ \mathrm{kJ} \times \frac{1\ \mathrm{mol}}{40.7\ \mathrm{kJ}} \times \frac{18.02\ \mathrm{g}}{1\ \mathrm{mol}} = 54.1\ \mathrm{g}$

Question 1

Which of the following best explains why water droplets form a spherical shape on a surface?

Accepted Answer

Intermolecular forces among water molecules minimize the surface area, resulting in a spherical shape.

Question 2

Which property distinguishes solids from liquids at the molecular level?

Accepted Answer

Solids have molecules that are fixed in position and only vibrate about a fixed point.

Question 3

A liquid with strong intermolecular forces will generally exhibit which of the following properties?

Accepted Answer

High surface tension and high viscosity.

Question 4

Which of the following statements about evaporation is correct?

Accepted Answer

Evaporation occurs more rapidly at higher temperatures and with weaker intermolecular forces.

Question 5

At the boiling point of a liquid, which condition is true?

Accepted Answer

The vapor pressure of the liquid equals the pressure above it.

Question 6

Calculate the mass of water (in grams) that can be vaporized at its boiling point with 122.1 kJ of heat. The heat of vaporization of water at 100°C is $40.7\ \mathrm{kJ/mol}$ and the molar mass of water is $18.02\ \mathrm{g/mol}$.

Accepted Answer

$122.1\ \mathrm{kJ} 	imes \frac{1\ \mathrm{mol}}{40.7\ \mathrm{kJ}} 	imes \frac{18.02\ \mathrm{g}}{1\ \mathrm{mol}} = 54.1\ \mathrm{g}$

Question 7

Which intermolecular force is present in all molecules and atoms, regardless of polarity?

Accepted Answer

Dispersion (London) force

Question 8

Why does water have a much higher boiling point than expected for its molar mass?

Accepted Answer

Water molecules form strong hydrogen bonds due to their polarity and bent geometry.

Question 9

Which of the following best describes the process of sublimation?

Accepted Answer

A solid changes directly into a gas without passing through the liquid phase.

Question 10

Which type of crystalline solid is held together by electrostatic attractions between cations and anions?

Accepted Answer

Ionic solid

Question 11

A student mixes pentane (C$_5$H$_{12}$, nonpolar) and water (polar) in a beaker. What will happen?

Accepted Answer

Pentane and water will separate into two layers because polar and nonpolar liquids are not miscible.

Question 12

Which of the following molecules can form hydrogen bonds?

Accepted Answer

NH$_3$

Question 13

Which intermolecular force is primarily responsible for the high viscosity of maple syrup compared to water?

Accepted Answer

Strong hydrogen bonding and/or dipole-dipole forces

Question 14

Which of the following is true about the melting of ice?

Accepted Answer

Melting is an endothermic process; heat is absorbed as ice turns to liquid water.

Question 15

Calculate the amount of heat (in kJ) required to melt 45.0 g of ice at 0°C. The heat of fusion for water is $6.02\ \mathrm{kJ/mol}$ and the molar mass of water is $18.02\ \mathrm{g/mol}$.

Accepted Answer

$45.0\ \mathrm{g} 	imes \frac{1\ \mathrm{mol}}{18.02\ \mathrm{g}} 	imes 6.02\ \mathrm{kJ} = 15.0\ \mathrm{kJ}$

Question 16

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

Accepted Answer

Hydrogen bonds hold the two strands of DNA together by pairing complementary bases.

Question 17

Which of the following statements about water is FALSE?

Accepted Answer

Water contracts upon freezing, making ice more dense than liquid water.

Question 18

Which type of atomic solid is held together by covalent bonds and has a very high melting point?

Accepted Answer

Covalent atomic solid

Question 19

Which intermolecular force is the strongest among the following?

Accepted Answer

Ion-dipole force

Liquids, Solids, and Intermolecular Forces: Structured Study Notes

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