Question 1

A solution is prepared by dissolving 15.0 g of urea (molar mass = 60.06 g/mol) in 100.0 g of water. The freezing point depression constant for water is $$K_f = 1.86\ \mathrm{^\circ C\,kg\,$$mol^{-1}$$}$$ and the normal freezing point of water is $$0.00\ \mathrm{^\circ C}. $$What is the freezing point of the solution?

Accepted Answer

$$-2.33\ \mathrm{^\circ C}$$

Question 2

A 50.0 g sample of ethanol ($$\mathrm{C_2H_5OH}$$, molar mass = 46.07 g/mol) is heated from $$-20.0\ \mathrm{^\circ C} to$$ $$78.0\ \mathrm{^\circ C} ($$its boiling point). The specific heat capacities are: solid = $$2.0\ \mathrm{J\,g$$^{-1}$$\,^\circ C$$^{-1}$$}$$, liquid = $$2.44\ \mathrm{J\,g$$^{-1}$$\,^\circ C$$^{-1}$$}$$, heat of fusion = $$104\ \mathrm{J\,g$$^{-1}$$}. $$How much energy (in kJ) is required for this process? (Assume no vaporization occurs.)

Accepted Answer

$$12.2\ \mathrm{kJ}$$

Question 3

A cubic unit cell contains 8 corner atoms and 1 atom at the center of the cube. What is the chemical formula if the corners are sodium (Na) and the center is chlorine (Cl)?

Accepted Answer

$$\mathrm{NaCl}$$

Question 4

The vapor pressure of acetone at $$25\ \mathrm{^\circ C} is$$ $$230\ \mathrm{torr}. $$Given that the heat of vaporization $$\Delta H_{vap} is$$ $$31.3\ \mathrm{kJ\,$$mol^{-1}$$}$$, what is the vapor pressure at $$45\ \mathrm{^\circ C}$$? (Use $$R = 8.314\ \mathrm{J\,$$mol^{-1}$$\,K$$^{-1}$$}.)$$

Accepted Answer

$$400\ \mathrm{torr}$$

Question 5

Which of the following substances would have the highest surface tension at room temperature?

A) $$\mathrm{CH_4$}

B$$) $$\mathrm{H_2O}

C$$) $$\mathrm{C_2H_6}

D$$) $$\mathrm{CO_2$}$$

Accepted Answer

$$\mathrm{H_2O}$$

Question 6

How does increasing temperature affect the viscosity of a typical liquid such as glycerol?

Accepted Answer

Viscosity decreases because intermolecular forces are overcome.

Question 7

Which solvent would best dissolve potassium iodide ($$\mathrm{KI}$$)?

Accepted Answer

Water ($$\mathrm{H_2O})$$

Question 8

Which of the following molecules would have the highest boiling point?

A) $$\mathrm{CH_3F}

B$$) $$\mathrm{CH_4$}

C$$) $$\mathrm{CH_3Cl}

D$$) $$\mathrm{CH_3Br}$$

Accepted Answer

$$\mathrm{CH_3Br}$$

Question 9

Refer to a typical phase diagram. What is the significance of the triple point?

Accepted Answer

It is the temperature and pressure where all three phases (solid, liquid, gas) coexist in equilibrium.

Question 10

On a phase diagram, what does the line separating the solid and liquid regions represent?

Accepted Answer

The melting/freezing point at different pressures.

Question 11

A solution is made by dissolving 10.0 g of glucose ($$\mathrm{C_6H_{12}O_6$}$$, molar mass = 180.16 g/mol) in 200.0 g of water. What is the molality of the solution?

Accepted Answer

$$0.278\ \mathrm{mol\,kg$$^{-1}$$}$$

Question 12

Which of the following substances exhibits only London dispersion forces as its primary intermolecular force?

A) $$\mathrm{NH_3$}

B$$) $$\mathrm{CO_2$}

C$$) $$\mathrm{H_2O}

D$$) $$\mathrm{CH_3Cl}$$

Accepted Answer

$$\mathrm{CO_2$}$$

Question 13

Which of the following would have the lowest vapor pressure at room temperature?

A) $$\mathrm{C_5H_{12}}

B$$) $$\mathrm{C_6H_{14}}

C$$) $$\mathrm{C_4H_{10}}

D$$) $$\mathrm{H_2O}$$

Accepted Answer

$$\mathrm{H_2O}$$

Question 14

A sample of ice at $$-10.0\ \mathrm{^\circ C} ($$specific heat $$2.09\ \mathrm{J\,g$$^{-1}$$\,^\circ C$$^{-1}$$}) is $$heated to liquid water at $$25.0\ \mathrm{^\circ C} ($$specific heat $$4.18\ \mathrm{J\,g$$^{-1}$$\,^\circ C$$^{-1}$$}). $$The heat of fusion is $$334\ \mathrm{J\,g$$^{-1}$$}. $$How much energy is required to heat 20.0 g of ice from $$-10.0\ \mathrm{^\circ C} to$$ $$25.0\ \mathrm{^\circ C}$$?

Accepted Answer

$$7.34\ \mathrm{kJ}$$

Question 15

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

Accepted Answer

Oil is nonpolar and water is polar.

Question 16

Which of the following molecules would have the strongest dipole-dipole interactions?

A) $$\mathrm{CO_2$}

B$$) $$\mathrm{CH_3F}

C$$) $$\mathrm{$$CCl_4$$}

D$$) $$\mathrm{CH_4$}$$

Accepted Answer

$$\mathrm{CH_3F}$$

Question 17

Which of the following statements about the critical point on a phase diagram is correct?

Accepted Answer

It is the temperature and pressure above which the gas and liquid phases are indistinguishable.

Question 18

Which of the following substances would exhibit the greatest capillary action in a glass tube?

A) Mercury

B) Water

C) Hexane

D) Bromine

Accepted Answer

Water

Question 19

If the vapor pressure of a liquid increases, what happens to its boiling point?

Accepted Answer

The boiling point decreases.

Liquids, Solids, and Intermolecular Forces: Final Exam Study Guide

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