Q: Calculate the mass of water (in grams) that can be vaporized at its boiling point with 155 kJ of heat. Use $$\Delta H_{\text{vap}} = 40.7\ \text{kJ/mol}$$ and $$\text{molar mass of H}_2\text{O} = 18.02\ \text{g/mol}.$$

$$155\ \text{kJ} \times \frac{1\ \text{mol H}_2\text{O}}{40.7\ \text{kJ}} \times \frac{18.02\ \text{g H}_2\text{O}}{1\ \text{mol H}_2\text{O}} = 68.6\ \text{g}$$

Q: Calculate the mass of ice (in grams) that absorbs 237 kJ of heat upon melting at 0 °C. Use $$\Delta H_{\text{fus}} = 6.02\ \text{kJ/mol}$$ and $$\text{molar mass of H}_2\text{O} = 18.02\ \text{g/mol}.$$

$$237\ \text{kJ} \times \frac{1\ \text{mol H}_2\text{O}}{6.02\ \text{kJ}} \times \frac{18.02\ \text{g H}_2\text{O}}{1\ \text{mol H}_2\text{O}} = 709\ \text{g}$$

Question 1

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

Accepted Answer

The presence of hydrogen bonds between water molecules.

Question 2

Which property distinguishes solids from liquids at the molecular level?

Accepted Answer

Solids have molecules fixed in position, only vibrating about a fixed point.

Question 3

A paper clip floats on water but sinks in gasoline. What is the best explanation for this observation?

Accepted Answer

Water has stronger intermolecular forces, resulting in higher surface tension.

Question 4

Which of the following statements about viscosity is correct?

Accepted Answer

Viscosity is the resistance of a liquid to flow and is higher in substances with stronger intermolecular forces.

Question 5

Which factor does NOT affect the vapor pressure of a liquid at equilibrium?

Accepted Answer

Surface area.

Question 6

Calculate the mass of water (in grams) that can be vaporized at its boiling point with 155 kJ of heat. Use $$\Delta H_{	ext{vap}} = 40.7\ 	ext{kJ/mol}$$ and $$	ext{molar mass of H}_2	ext{O} = 18.02\ 	ext{g/mol}.$$

Accepted Answer

$$155\ 	ext{kJ} 	imes \frac{1\ 	ext{mol H}_2	ext{O}}{40.7\ 	ext{kJ}} 	imes \frac{18.02\ 	ext{g H}_2	ext{O}}{1\ 	ext{mol H}_2	ext{O}} = 68.6\ 	ext{g}$$

Question 7

Which of the following is an example of a physical change that is exothermic?

Accepted Answer

Condensation of steam.

Question 8

Why does sweating cool the human body?

Accepted Answer

Sweat absorbs heat from the body as it evaporates, because evaporation is endothermic.

Question 9

Which intermolecular force is present in all molecules and atoms?

Accepted Answer

Dispersion force.

Question 10

Which molecule will have the highest boiling point due to hydrogen bonding?

Accepted Answer

Water ($$	ext{H}_2	ext{O})$$

Question 11

Which of the following statements about the melting of ice is correct?

Accepted Answer

Melting is endothermic because heat is absorbed to overcome intermolecular forces.

Question 12

Calculate the mass of ice (in grams) that absorbs 237 kJ of heat upon melting at 0 °C. Use $$\Delta H_{	ext{fus}} = 6.02\ 	ext{kJ/mol}$$ and $$	ext{molar mass of H}_2	ext{O} = 18.02\ 	ext{g/mol}.$$

Accepted Answer

$$237\ 	ext{kJ} 	imes \frac{1\ 	ext{mol H}_2	ext{O}}{6.02\ 	ext{kJ}} 	imes \frac{18.02\ 	ext{g H}_2	ext{O}}{1\ 	ext{mol H}_2	ext{O}} = 709\ 	ext{g}$$

Question 13

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

Accepted Answer

Ionic solid.

Question 14

Which of the following best describes the structure of a metallic atomic solid?

Accepted Answer

Positively charged ions in a sea of electrons.

Question 15

Why does ice float on water?

Accepted Answer

Ice expands upon freezing, making it less dense than liquid water.

Question 16

Which intermolecular force is responsible for the high boiling point of water compared to other molecules of similar molar mass?

Accepted Answer

Hydrogen bonding.

Question 17

Which of the following is NOT eliminated from water by boiling?

Accepted Answer

Chemical contaminants such as mercury and lead.

Question 18

Which of the following statements about DNA is correct?

Accepted Answer

DNA strands are held together by hydrogen bonds between complementary bases.

Liquids, Solids, and Intermolecular Forces: Structured Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard