Practice Problems

What are the signs of ΔG, ΔH, and ΔS for water condensing at 105°C?

a) +, -, -

b) -, -, -

c) +, +, +

d) -, +, -

A

For the combustion of hydrogen below, why does a hydrogen balloon stop exploding at 5500 K? 2 H2 (g) + O2 (g) → 2 H2O (g)

a) That makes no sense. Hydrogen balloons should explode even more readily at higher temperatures.

b) Combustion of H2 has a negative entropy and therefore an upper limit for the temperature at which it can react

c) Combustion of H2 has a negative enthalpy and therefore an upper limit for the temperature at which it can react

d) Combustion of H2 does work on the system and therefore an upper limit for the temperature at which it can react

B

ΔG for water boiling at 85°C (<0, =0, >0) and at 100°C is (<0, =0, >0).

a) <0, <0

b) >0, >0

c) <0, >0

d) >0, =0

e) <0, =0

D

Which of the following statements are true? I. Vapor pressure is a surface phenomenon II. The smaller the IMF, the smaller the vapor pressure III. The volume of a liquid does not affect the vapor pressure IV. Vapor pressure is temperature dependent

a) I, II, III, and IV

b) I, III, and IV

c) II, III, and IV

d) I and III

B

What is ΔHvap of a compound if its vapor pressure increases from 200

torr at 300K to 600 torr at 333K?

a) 2.7 kJ/mol

b) 0.27 kJ/mol

c) 27 kJ/mol

C

Which of the following statements is true?

a) Heat of vaporization decreases as IMFs increase.

b) Heat of vaporization is exothermic as it describes the

phase change of gas to liquid.

c) Vapor pressure is a bulk phenomenon.

d) The Clausius-Clapeyron equation assumes equilibrium

between liquid and gaseous phases of a substance.

D

Which of the following is true

regarding the phase diagram of

sulfur to the right?

a) Rhombic sulfur cannot be

directly converted to liquid.

b) Monoclinic sulfur does not

sublime.

c) Sulfur has 3 triple points

d) Sulfur has 2 triple points.

e) Sulfur has 0 triple points

C

Using the phase diagram for water on this page, what occurs after

increasing temperature from -5°C to 100°C at a constant pressure of 0.5

atm?

a) Solid water is melted, resulting in liquid water.

b) Solid water is melted then boiled, resulting in water vapor.

c) Liquid water is boiled, resulting in water vapor.

d) There is no change in the state because pressure isn’t high

enough.

B

How much heat is required to heat 0.1 g of ice at -30°C to steam at 100°C?

Use the constants provided on the left.

a) 80 J

b) 193 J

c) 306 J

d) 74 J

C

Which of the species below would be expected to be the

most miscible in benzene (C6H6)?

a) Decane, C10H22

b) Sugar, C6H12O6

c) Hydrogen fluoride, HF

d) Methanol, CH3OH

A

The solubility of KBr in water increases with temperature. Which

of the following cases for ΔHC.L., ΔHhyd, and ΔHsoln is consistent

with this observation? All values are in kJ/mole.

a) -670, 690, 20

b) 690, -670, 20

c) 670, -690, -20

d) -690, 670, -20

B

Which of the following statements about solubility of gases in

water is true?

a) The ΔSsoln and the ΔHsoln are both positive.

b) The solubility generally increases with increasing

water temperature

c) The small bubbles that initially form in water as it

heats signify the onset of boiling.

d) CO2 is highly soluble in water because it reacts to form

carbonic acid

D

At 40°C the vapor pressure of water is 55 torr, and the vapor

pressure of isopropyl alcohol is 100 torr. What would the

vapor pressure be if 0.3 moles of water are mixed with 14.2

moles of isopropyl alcohol?

a) 99 torr

b) 40 torr

c) 100 torr

d) 55 torr

A

Which of the following is not related to colligative properties?

a) Mixing water and anti-freeze to improve radiator

fluid’s freezing/boiling point.

b) Applying a pressure across a semi-permeable

membrane to force pure water across.

c) Adding lots of salt to ice to lower its freezing point

when making ice cream.

d) Water boiling at 75°C instead of 100°C high in the

Himalayan mountains

D

Assuming standard conditions and given kf =2 and kb = 0.5 for water, what would

be the freezing point for a solution of sugar water that boiled at 374.5 K? (Recall

that the normal boiling point for water is 373 K).

a) 272 K

b) 261 K

c) 267 K

d) 0 K

C

What is Kc for the reaction below?

H2O2 (l) → H2O (l) + O2 (g)

a) K = [O2]

b) K = [O2][H2O][H2O2]^-1

c) K = [H2O][H2O2]^-1

d) K = [O2][H2O]

A

The reaction 2A → B + C has a Kc of 0.2. The reaction is commenced

with initial concentrations [A] = 0.2 M, [B] = 0.2 M and [C] = 0.2 M.

In what direction does the reaction occur?

a) The reaction shifts to the right to reach equilibrium.

b) The reaction shifts to the left to reach equilibrium

c) The reaction is already at equilibrium.

d) Cannot be determined without knowing the temperature.

B

Consider the reaction below where Kp = 2.0. If there is initially 2.0

atm HBr, how much H2 will there be at equilibrium?

Br2 (l) + H2 (g) ⇌ 2 HBr (g)

a) 0.5 atm

b) 1.0 atm

c) 1.5 atm

d) 0.25 atm

A

The combustion of methane below will shift to the right under

which circumstances?

CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O(g)

I. Increasing the temperature

II. Increasing the pressure

III. Increasing the concentration of CO2

IV. Increasing the concentration of CH4

a) I, II, III, IV

b) I, II, IV

c) II only

d) I, II, III

e) II, III

f) IV only

F

Consider a reaction with ΔHrxn = -212 J. Which pair of K values and temperatures is

possible for this reaction?

a) None of these.

b) K1 = 10.5, T1 = 100 K ; K2 = 9.33, T2 = 327 K

c) K1 = 21, T1 = 111 K ; K2 = 21, T2 = 316 K

d) K1 = 14.6, T1 = 122 K ; K2 = 16.6, T2 = 315 K

B

What is a good estimate of ΔG^o if K = 1017 at room

temperature?

a) 100 kJ/mol

b) -100 kJ/mol

c) 600 kJ/mol

d) -600 kJ/mol

B