Q: Which equation would you use to calculate the heat required to melt 2.00 moles of ice at 0$$^ ext{o}C$$, given the heat of fusion of water is 6.02 kJ/mol?

$$q = n \times \Delta H_{fus}$$

Question 1

Which of the following best explains why water forms a nearly perfect sphere in the absence of gravity, such as on the International Space Station?

Accepted Answer

Intermolecular forces cause water molecules to stick together, minimizing surface area.

Question 2

Which of the following statements about the density of water is TRUE and has significant biological implications?

Accepted Answer

Liquid water is denser than ice, allowing ice to float and insulate aquatic life.

Question 3

Which state of matter is compressible and why?

Accepted Answer

Gas, because there is a large amount of empty space between particles.

Question 4

Which of the following best describes the difference between crystalline and amorphous solids?

Accepted Answer

Crystalline solids have a regular, repeating structure, while amorphous solids lack long-range order.

Question 5

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

Accepted Answer

Dispersion (London) forces

Question 6

Why does iodine (I$$_2) $$have a higher boiling point than bromine (Br$$_2) or $$chlorine (Cl$$_2$$)?

Accepted Answer

Iodine has a larger molar mass, leading to stronger dispersion forces.

Question 7

Which of the following molecules would you expect to have the highest boiling point, and why?

Accepted Answer

CH$$_3OH$$, because it can hydrogen bond.

Question 8

Which of the following best explains why water has a concave meniscus in a glass tube?

Accepted Answer

Adhesive forces between water and glass are stronger than cohesive forces among water molecules.

Question 9

A 100 mL sample of water is placed in two different beakers: one at 25$$^	ext{o}C $$and one at 55$$^	ext{o}C. $$Which sample will have the greatest rate of vaporization and why?

Accepted Answer

The sample at 55$$^	ext{o}C$$, because higher temperature increases the fraction of molecules with enough energy to escape.

Question 10

Which of the following statements about vapor pressure is correct?

Accepted Answer

Vapor pressure increases as temperature increases.

Question 11

Which equation would you use to calculate the heat required to melt 2.00 moles of ice at 0$$^	ext{o}C$$, given the heat of fusion of water is 6.02 kJ/mol?

Accepted Answer

$$q = n 	imes \Delta H_{fus}$$

Question 12

A sample of water is heated from $$-25.0\ ^\circ\mathrm{C} to$$ $$0.0\ ^\circ\mathrm{C}. $$Which equation would you use to calculate the energy absorbed during this process?

Accepted Answer

$$q = m 	imes C_s 	imes \Delta T$$

Question 13

Which of the following best describes the process of sublimation?

Accepted Answer

A solid turns directly into a gas.

Question 14

Which of the following is the strongest type of intermolecular force present in a mixture of NaCl dissolved in water?

Accepted Answer

Ion–dipole forces

Question 15

Which of the following factors will increase the viscosity of a liquid?

Accepted Answer

Increasing the strength of intermolecular forces

Question 16

Which of the following best explains why n-pentane has a higher boiling point than neopentane, even though they have the same molar mass?

Accepted Answer

n-Pentane has more surface-to-surface contact, leading to stronger dispersion forces.

Question 17

A phase diagram shows a substance with a triple point at $$-24.5\ ^\circ\mathrm{C}$$ and 225 mmHg. What will happen to a solid sample at 220 mmHg as it is warmed from $$-35\ ^\circ\mathrm{C} to$$ $$0\ ^\circ\mathrm{C}$$?

Accepted Answer

The solid sublimes into a gas.

Question 18

Which of the following is TRUE about the heat of vaporization ($$\Delta H_{vap}) $$and the heat of fusion ($$\Delta H_{fus}) $$for a given substance?

Accepted Answer

$$\Delta H_{vap} is $$always greater than $$\Delta H_{fus}.$$

Question 19

Which of the following best describes the effect of increasing external pressure on the boiling point of water?

Accepted Answer

The boiling point increases.

Liquids, Solids, and Intermolecular Forces: Study Notes

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