Chemistry and Chemical Reactivity 9th Edition By Kotz – Test Bank

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Sample Questions Posted Below

 

 

 

 

MULTIPLE CHOICE

 

  1. The energy stored in a fuel is called _____.
a. heat
b. internal energy
c. temperature
d. kinetic energy
e. potential energy

 

 

ANS:  E

 

  1. Which of the following statements is/are CORRECT?
  1. A system is defined as an object or collection of objects being studied.
  2. Surroundings are defined as the entire universe, including the system.
  3. In an endothermic reaction, heat is transferred from the system to the surroundings.

 

a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3

 

 

ANS:  A

 

  1. A hot piece of iron is dropped into a beaker containing colder water. Which of the following statements is/are CORRECT?
  1. Energy is transferred as heat from the iron to the water.
  2. Thermal equilibrium is attained when the iron and the water reach the same temperature.
  3. Thermal energy from the iron is converted to electrostatic energy in the water.

 

a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

 

 

ANS:  D

 

  1. Which one of the following statements is INCORRECT?
a. Energy is neither created nor destroyed in chemical reactions.
b. Kinetic energy is the energy that results from an object’s position.
c. Exothermic processes transfer heat from the system into the surroundings.
d. Increasing the thermal energy of a gas increases the motion of its atoms.
e. Energy is the capacity to do work.

 

 

ANS:  B

 

  1. Many homes are heated using natural gas. The combustion of natural gas converts
a. chemical potential energy to thermal energy.
b. thermal energy to mechanical energy.
c. mechanical energy to chemical potential.
d. electrostatic energy to mechanical energy.
e. gravitational energy to acoustic energy.

 

 

ANS:  A

 

 

  1. Which of these physical changes would require the release of energy?
a. condensing a gas
b. boiling a liquid
c. melting a solid
d. all of these
e. none of these

 

 

ANS:  A

 

  1. Which of the following processes is/are endothermic?
  1. the combustion of hydrogen
  2. the condensation of water
  3. the evaporation of isopropyl alcohol

 

a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3

 

 

ANS:  C

 

  1. Which of the following processes is/are exothermic?
  1. the reaction of butane with oxygen
  2. the melting of gold
  3. cooling copper from 225 °C to 65 °C

 

a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3

 

 

ANS:  D

 

  1. Which of the following is an endothermic process?
a. work is done by the system on the surroundings
b. heat energy flows from the system to the surroundings
c. work is done on the system by the surroundings
d. heat energy is evolved by the system
e. none of the above

 

 

ANS:  C

 

  1. Specific heat capacity is
a. the quantity of heat needed to change the temperature of 1.00 g of a substance by 1 K.
b. the quantity of heat needed to change the temperature of 1.00 g of a substance by 4.184 K.
c. the capacity of a substance to gain or lose a 1.00 J of energy in the form of heat.
d. the temperature change undergone when 1.00 g of a substance absorbs 4.184 J.
e. the maximum amount of energy in the form of heat that 1.00 g of a substance may absorb without decomposing.

 

 

ANS:  A

 

 

  1. It is relatively easy to change the temperature of a substance that
a. is very massive.
b. is an insulator.
c. has a high specific heat capacity.
d. has a low specific heat capacity.
e. is brittle.

 

 

ANS:  D

 

  1. Heat capacity is defined as
a. the amount of heat required to raise the temperature of 1 gram of substance by 1 K.
b. the amount of heat required to raise the temperature of a substance by 1 K.
c. the amount of heat required to vaporize a solid or liquid.
d. the maximum amount of heat that a substance may absorb without decomposing.
e. 4.18 cal/g×K.

 

 

ANS:  B

 

  1. The specific heat capacity of copper is 0.384 J/g×°C.  What is the molar specific heat capacity of this substance?  The molar mass of copper is 63.54 g/mol.
a. 24.4 J/mol×°C
b. 0.00604 J/mol×°C
c. 165 J/mol×°C
d. 0.384 J/mol×°C
e. 2.60 J/mol×°C

 

 

ANS:  A

 

  1. Which of the following statements is/are CORRECT?
  1. Specific heat capacity is a positive value for liquids and solids and a negative value for gases.
  2. The larger the heat capacity of an object, the more thermal energy it can store.
  3. When heat is transferred from the surroundings to the system, q is negative.

 

a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

 

 

ANS:  B

 

  1. Exactly 212.2 J will raise the temperature of 10.0 g of a metal from 25.0 °C to 60.0 °C. What is the specific heat capacity of the metal?
a. 0.606 J/(g·°C)
b. 1.65 J/(g·°C)
c. 14.5 J/(g·°C)
d. 50.8 J/(g·°C)
e. none of these

 

 

ANS:  A

 

 

  1. A 100 g sample of each of the following metals is heated from 35°C to 45°C.  Which metal absorbs the greatest amount of heat energy?
Metal Specific Heat Capacity
copper 0.385 J/(g·°C)
magnesium 1.02 J/(g·°C)
mercury 0.138 J/(g·°C)
silver 0.237 J/(g·°C)
lead 0.129 J/(g·°C)

 

a. magnesium b. lead c. mercury d. silver e. copper

 

 

ANS:  A

 

 

  1. If 50.0 g of benzene, C6H6, at 25.0 °C absorbs 2.71 kJ of energy in the form of heat, what is the final temperature of the benzene? The specific heat capacity of benzene is 1.72 J/g×K.
a. 25.0 °C b. 31.5 °C c. 56.5 °C d. 32.3 °C e. 57.3 °C

 

 

ANS:  C

 

  1. How much energy is gained by nickel when 18.7 g of nickel is warmed from 20.5 °C to 79.8 °C?  The specific heat capacity of nickel is 0.443 J/(g·°C).
a. 1.70 ´ 102 J b. 35.35 J c. 26.27 J d. 4.91 ´ 102 J e. 6.61 ´ 102 J

 

 

ANS:  D

 

  1. If 35.0 g H2O at 22.7 °C is combined with 65.0 g H2O at 87.5 °C, what is the final temperature of the mixture? The specific heat capacity of water is 4.184 J/g×K.
a. 25.1 °C b. 45.4 °C c. 50.8 °C d. 64.8 °C e. 48.9 °C

 

 

ANS:  D

 

  1. A 170.0-g sample of metal at 79.00°C is added to 170.0 g of H2O(l) at 14.00°C in an insulated container.  The temperature rises to 16.19°C.  Neglecting the heat capacity of the container, what is the specific heat capacity of the metal?  The specific heat capacity of H2O(l) is 4.18 J/(g·°C).
a. 4.18 J/(g·°C)
b. 120 J/(g·°C)
c. 0.146 J/(g·°C)
d. –0.146 J/(g·°C)
e. 28.6 J/(g·°C)

 

 

ANS:  C

 

  1. If 46.1 g Cu at 11.6 °C is placed in 85.0 g H2O at 72.4 °C, what is the final temperature of the mixture? The specific heat capacities of copper and water are 0.385 J/g×K and 4.184 J/g×K, respectively.
a. 71.2 °C b. 63.6 °C c. 51.0 °C d. 42.0 °C e. 69.5 °C

 

 

ANS:  E

 

 

  1. Which of the following processes will result in the lowest final temperature of the metal–water mixture at when thermal equilibrium is reached?  The specific heat capacity of nickel is 0.443 J/(g·°C). The specific heat capacity of water is 4.184 J/(g·°C).
a. the addition of 100 g of nickel at 95°C to 80 mL of water at 25°C in an insulated container
b. the addition of 100 g of nickel at 95°C to 100 mL of water at 25°C in an insulated container
c. the addition of 100 g of nickel at 95°C to 40 mL of water at 25°C in an insulated container
d. the addition of 100 g of nickel at 95°C to 20 mL of water at 25°C in an insulated container
e. the addition of 100 g of nickel at 95°C to 60 mL of water at 25°C in an insulated container

 

 

ANS:  B

 

  1. When 66.0 g of an unknown metal at 28.5 °C is placed in 83.0 g H2O at 78.5 °C, the water temperature decreases to 75.9 °C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g×K.
a. 0.055 J/g×K
b. 0.29 J/g×K
c. 0.69 J/g×K
d. 0.18 J/g×K
e. 2.6 J/g×K

 

 

ANS:  B

 

  1. A 41.3-g piece of nickel (s = 0.443 J/(g·°C)), initially at 255.8°C, is added to 144.8 g of a liquid, initially at 23.1°C, in an insulated container.  The final temperature of the metal–liquid mixture at equilibrium is 35.4°C.  What is the identity of the liquid?  Neglect the heat capacity of the container.
a. acetone (s = 2.15 J/(g·°C))
b. hexane (s = 2.27 J/(g·°C))
c. water (s = 4.18 J/(g·°C))
d. methanol (s = 2.53 J/(g·°C))
e. ethanol (s = 2.43 J/(g·°C))

 

 

ANS:  B

 

  1. How much energy is needed to convert 57.5 grams of ice at 0.00°C to liquid water at 75.0°C?

specific heat capacity (ice) = 2.10 J/g°C

specific heat capacity (liquid water) = 4.18 J/g°C

heat of fusion = 333 J/g

heat of vaporization = 2258 J/g

a. 18.0 kJ b. 2.06 kJ c. 28.2 kJ d. 37.2 kJ e. 148 kJ

 

 

ANS:  D

 

  1. Calculate the energy in the form of heat (in kJ) required to convert 325 grams of liquid water at 20.0 °C to steam at 115 °C. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: liquid water = 4.184 J/g×K, steam = 1.92 J/g×K)
a. 129 kJ b. 121 kJ c. 851 kJ d. 914 kJ e. 735 kJ

 

 

ANS:  C

 

  1. Calculate the energy in the form of heat (in kJ) required to change 71.8 g of liquid water at 25.7 °C to ice at –16.1 °C. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)
a. –12.6 kJ b. –7.7 kJ c. –34.0kJ d. –31.6 kJ e. –10.1 kJ

 

 

ANS:  C

 

 

  1. 44.0 g of ice at –20.0 °C is mixed with 325 g of water at 32.1 °C. Calculate the final temperature of the mixture. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)
a. –0.6 °C b. 5.5 °C c. 12.1 °C d. 17.6 °C e. 38.9 °C

 

 

ANS:  D

 

  1. What is the minimum mass of ice at 0.0 °C that must be added to 1.00 kg of water to cool the water from 28.0 °C to 12.0 °C? (Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)
a. 175 g b. 201 g c. 244 g d. 299 g e. 1140 g

 

 

ANS:  A

 

  1. The heat of vaporization of benzene, C6H6, is 30.7 kJ/mol at its boiling point of 80.1 °C. How much energy in the form of heat is required to vaporize 102 g benzene at its boiling point?
a. 0.302 kJ
b. 23.6 kJ
c. 24.2 kJ
d. 40.1 kJ
e. 3.14 ´ 103 kJ

 

 

ANS:  D

 

  1. One statement of the first law of thermodynamics is that
a. the amount of work done on a system is dependent of the pathway.
b. the total work done on a system must equal the heat absorbed by the system.
c. the total work done on a system is equal in magnitude, but opposite in sign of the heat absorbed by the system.
d. the total energy change for a system is equal to the sum of the heat transferred to or from the system and the work done by or on the system.
e. in any chemical process the heat flow must equal the change in enthalpy.

 

 

ANS:  D

 

  1. Which of the following statements is/are CORRECT?
  1. If a reaction occurs at constant pressure, q = DH.
  2. The change in energy for a system is defined as the sum of the energies transferred as heat and work (i.e., DU = q + w).
  3. If a reaction occurs at constant volume, q = w

 

a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

 

 

ANS:  D

 

  1. Which of the following thermodynamic quantities are state functions: heat (q), work (w), enthalpy change (DH), and/or internal energy change (DU)?
a. q only b. w only c. DH only d. DU only e. DH and DU

 

 

ANS:  E

 

  1. Calculate DU of a gas for a process in which the gas absorbs 19 J of heat and does 49 J of work by expanding.
a. 30 J
b. 68 J
c. –68 J
d. 0, because DU is a state function
e. –30 J

 

 

ANS:  E

 

  1. What is the change in internal energy of the system (DU) if 7 kJ of heat energy is evolved by the system and 99 kJ of work is done on the system for a certain process?
a. 92 kJ b. –106 kJ c. –7 kJ d. –92 kJ e. 106 kJ

 

 

ANS:  A

 

 

  1. If q = 98 kJ and w = 4 kJ for a certain process, that process
a. requires a catalyst.
b. is endothermic.
c. occurs slowly.
d. is exothermic.
e. cannot occur.

 

 

ANS:  B

 

  1. Given the thermochemical equation

AlCl3(s) + O2(g  ® 2Al2O3(s) + 6Cl2(g); Dr = –529 kJ/mol-rxn

find Dr for the following reaction.

Al2O3(s) +  Cl2(g) ® AlCl3(s) + O2(g)

a. +88.2 kJ/mol-rxn
b. +264.5 kJ/mol-rxn
c. +529.0 kJ/mol-rxn
d. +176.3 kJ/mol-rxn
e. -176.3 kJ/mol-rxn

 

 

ANS:  A

 

 

  1. The thermochemical equation for the combustion of methanol is shown below.
  CH3OH() + 3/2 O2(g) ® CO2(g) + 2 H 2O(g) DrH° = –638.7 kJ/mol-rxn

What is the enthalpy change for the combustion of 8.59 g CH3OH?

a. –171 kJ
b. –19.9 kJ
c. –2.38 ´ 103 kJ
d. –5.49 ´ 103 kJ
e. –1.76 ´ 106 kJ

 

 

ANS:  A

 

  1. The thermochemical equation for the combustion of butane is shown below.
  C4H10(g) + 13/2 O2(g) ® 4 CO2(g) + 5 H2O() DrH° = –2877 kJ/mol-rxn

What is the enthalpy change for the following reaction?

8 CO2(g) + 10 H2O() ® 2 C4H10(g) + 13 O2(g)

a. +1439 kJ/mol-rxn
b. +2877 kJ/mol-rxn
c. –5754 kJ/mol-rxn
d. –2877 kJ/mol-rxn
e. +5754 kJ/mol-rxn

 

 

ANS:  E

 

  1. At constant pressure and 25°C, what is DrH° for the following reaction

2C2H6(g) + 7O2(g) ® 4CO2(g) + H2O(l)

if the complete consumption of 89.4 g of C2H6 liberates –4638 kJ of heat energy?

a. –3120 kJ/mol-rxn
b. –1560 kJ/mol-rxn
c. –27600 kJ/mol-rxn
d. –13800 kJ/mol-rxn
e. –787 kJ/mol-rxn

 

 

ANS:  A

 

  1. What quantity, in moles, of oxygen is consumed when 369.3 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?

H2(g) + O2(g)  ®  H2O(l); DrH° = –285.8 kJ/mol-rxn

a. 0.6461 mol b. 1.292 mol c. 0.3869 mol d. 1.146 mol e. 0.1461 mol

 

 

ANS:  A

 

 

  1. Iron oxide reacts with aluminum in an exothermic reaction.

Fe2O3(s) + 2 Al(s) ® 2 Fe(s) + Al2O3(s)

The reaction of 5.00 g Fe2O3 with excess Al(s) evolves 26.6 kJ of energy in the form of heat. Calculate the enthalpy change per mole of Fe2O3 reacted.

a. –5.32 kJ/mol
b. –1.33 ´ 102 kJ/mol
c. –2.12 ´ 104 kJ/mol
d. –2.12 ´ 102 kJ/mol
e. –8.50 ´ 102 kJ/mol

 

 

ANS:  E

 

  1. How much heat is liberated at constant pressure if 0.834 g of calcium carbonate reacts with 48.9 mL of 0.668 M hydrochloric acid?

CaCO3(s) + 2HCl(aq)  ®  CaCl2(aq) + H2O(l) + CO2(g); DrH° = –15.2 kJ/mol-rxn

a. –0.127 kJ b. –0.375 kJ c. –12.7 kJ d. –0.248 kJ e. –10.2 kJ

 

 

ANS:  A

 

 

  1. Hydrazine, N2H4, is a liquid used as a rocket fuel. It reacts with oxygen to yield nitrogen gas and water.

N2H4() + O2(g) ® N2(g) + 2 H2O()

The reaction of 6.50 g N2H4 evolves 126.2 kJ of heat. Calculate the enthalpy change per mole of hydrazine combusted.

a. –19.4 kJ/mol
b. –25.6 kJ/mol
c. –126 kJ/mol
d. –622 kJ/mol
e. –820. kJ/mol

 

 

ANS:  D

 

  1. CaO(s) reacts with water to form Ca(OH)2(aq). If 6.50 g CaO is combined with 99.70 g H2O in a coffee cup calorimeter, the temperature of the resulting solution increases from 21.7 °C to 43.1 °C. Calculate the enthalpy change for the reaction per mole of CaO. Assume that the specific heat capacity of the solution is 4.18 J/g×K.
a. –1.45 kJ/mol
b. –82.0 kJ/mol
c. –9.42 kJ/mol
d. –165 kJ/mol
e. –532 kJ/mol

 

 

ANS:  B

 

 

  1. Commercial cold packs consist of solid ammonium nitrate and water. NH4NO3 absorbs 25.69 kJ of heat per mole dissolved in water. In a coffee-cup calorimeter, 5.60 g NH4NO3 is dissolved in 100.0 g of water at 22.0 °C. What is the final temperature of the solution? Assume that the solution has a specific heat capacity of 4.18 J/g×K.
a. 0.0 °C
b. 17.9 °C
c. 11.6 °C
d. –54.8 °C
e. 26.1 °C

 

 

ANS:  B

 

  1. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 25.18 °C to 47.53 °C. What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g×K.
a. –116 J/g
b. –934 J/g
c. –1.03 ´ 103 J/g
d. –2.19 ´ 103 J/g
e. –1.03 ´ 104 J/g

 

 

ANS:  C

 

  1. When 50.0 mL of 1.30 M of HCl(aq) is combined with 50.0 mL of 1.20 M of NaOH(aq) in a coffee-cup calorimeter, the temperature of the solution increases by 8.01°C. What is the change in enthalpy for this balanced reaction?

HCl(aq) + NaOH(aq)  ®  NaCl(aq) + H2O(l)

Assume that the solution density is 1.00 g/mL and the specific heat capacity of the solution is 4.18 J/g×°C.

 

a. –55.8 kJ b. 55.8 kJ c. 51.5 kJ d. –51.5 kJ e. –26.8 kJ

 

 

ANS:  A

 

 

  1. When 0.236 mol of a weak base (A) is reacted with excess HCl, 6.91 kJ of energy is released as heat. What is DH for this reaction per mole of A consumed?
a. –34.2 kJ/mol
b. –59.4 kJ/mol
c. –29.3 kJ/mol
d. 34.2 kJ/mol
e. 29.3 kJ/mol

 

 

ANS:  C

 

 

 

  1. A chemical reaction in a bomb calorimeter evolves 3.86 kJ of energy in the form of heat. If the temperature of the bomb calorimeter increases by 4.17 K, what is the heat capacity of the calorimeter?
a. 3.87 ´ 103 J/K
b. 311 J/K
c. 926 J/K
d. 1.8 ´ 103 J/K
e. 1.61 ´ 104 J/K

 

 

ANS:  C

 

  1. A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.105-g sample of a certain hydrocarbon was burned in this calorimeter, the temperature increased by 2.14 K. Calculate the energy of combustion for 1 g of the hydrocarbon.
a. –5.29 J/g
b.  J/g
c. –0.120 J/g
d.  J/g
e. –0.560 J/g

 

 

ANS:  B

 

 

  1. A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.123-g sample of ethylene (C2H4) was burned in this calorimeter, the temperature increased by 2.50 K. Calculate the enthalpy change per mole of ethylene combusted.
a. –5.29 kJ/mol
b. –50.2 kJ/mol
c. –563 kJ/mol
d. –0.304 kJ/mol
e. –1.41 ´ 103 kJ/mol

 

 

ANS:  E

 

 

  1. Combustion of 7.21 g of liquid benzene (C6H6) causes a temperature rise of 50.3°C in a constant-pressure calorimeter that has a heat capacity of 5.99 kJ/°C.  What is DH for the following reaction?

C6H6(l) + O2(g)  ®  6CO2(g) + 3H2O(l)

a. –302 kJ/mol-rxn
b. 41.8 kJ/mol-rxn
c. –41.8 kJ/mol-rxn
d. –3.27 ´ 103 kJ/mol-rxn
e. 302 kJ/mol-rxn

 

 

ANS:  D

 

 

 

  1. Acetylene, C2H2, is a gas used in welding. The molar enthalpy of combustion for acetylene is –2599 kJ. A mass of 0.338 g C2H2(g) is combusted in a bomb calorimeter. If the heat capacity of the calorimeter is 729 J/K and it contains 1.150 kg of water, what is the temperature increase of the bomb calorimeter? The specific heat capacity of water is 4.184 J/g×K and the molar mass of acetylene is 26.04 g/mol.
a. 1.59 K b. 6.09 K c. 7.01 K d. 12.3 K e. 18.0 K

 

 

ANS:  B

 

  1. The overall chemical equation resulting from the sum of the following three steps is

 

2C(s) + 2H2O(g) ® 2CO(g) + 2H2(g)

CO(g) + H2O(g) ® CO2(g) + H2(g)

CO(g) + 3H2(g) ® CH4(g) + H2O(g)

 

a. 2C(s) + 2H2O(g) ® CO2(g) + CH4(g)
b. 2C(s) + 3H2O(g) ® CO(g) + CO2(g) + 3H2(g)
c. 2C(s) + H2O(g) + H2(g)® CO(g) + CH4(g)
d. 2CO(g) + 2H2(g) ® CH4(g) + CO2(g)
e. 2C(s) + CH4(g) + 3H2O(g) ® 3CO(g) + 5H2(g)

 

 

ANS:  A

 

  1. Determine the heat of evaporation of carbon disulfide,

CS2() ® CS2(g)

given the enthalpies of reaction below.

  C(s) + 2 S(s) ® CS2() DrH° = +89.4 kJ/mol-rxn
  C(s) + 2 S(s) ® CS2(g) DrH° = +116.7 kJ/mol-rxn

 

a. –206.1 kJ
b. –27.3 kJ
c. +27.3 kJ
d. +206.1 kJ
e. +1.31 kJ

 

 

ANS:  C

 

  1. Which of the following has a standard enthalpy of formation value of zero at 25°C?
a. I(g) b. I2(l) c. I2(s) d. I(s) e. I2(g)

 

 

ANS:  C

 

 

 

  1. Determine the standard enthalpy of formation of Fe2O3(s) given the thermochemical equations below.
  Fe(s) + 3 H2O() ® Fe(OH)3(s) + 3/2 H2(g) DrH° = +160.9 kJ/mol-rxn
  H2(g) + 1/2 O2(g) ® H2O() DrH° = –285.8 kJ/mol-rxn
  Fe2O3(s) + 3 H2O() ® 2 Fe(OH)3(s) DrH° = +288.6 kJ/mol-rxn

 

a. –252.6 kJ/mol-rxn
b. +163.7 kJ/mol-rxn
c. –824.2 kJ/mol-rxn
d. +33.2 kJ/mol-rxn
e. + 890.6 kJ/mol-rxn

 

 

ANS:  C

 

  1. Using the following thermochemical data:
2Ho(s) + 6HF(g) ® 2HoF3(s) + 3H2(g) DrH° = –1787.4 kJ/mol-rxn
2Ho(s) + 6HCl(g) ® 2HoCl3(s) + 3H2(g) DrH° = –1457.0 kJ/mol-rxn

calculate DrH° for the following reaction:

HoF3(s) + 3HCl(g) ® HoCl3(s) + 3HF(g)

a. –3244.4 kJ/mol-rxn
b. 330.4 kJ/mol-rxn
c. 165.2 kJ/mol-rxn
d. 660.8 kJ/mol-rxn
e. –1622.2 kJ/mol-rxn

 

 

ANS:  C

 

 

  1. Determine the enthalpy change for the decomposition of calcium carbonate

CaCO3(s) ® CaO(s) + CO2(g)

given the thermochemical equations below.

  Ca(OH)2(s) ® CaO(s) + H2O() DrH° = 65.2 kJ/mol-rxn
  Ca(OH)2(s) + CO2(g) ® CaCO3(s) + H2O() DrH° = -113.8 kJ/mol-rxn
  C(s) + O2(g) ® CO2(g) DrH° = -393.5 kJ/mol-rxn
  2 Ca(s) + O2(g) ® 2 CaO(s) DrH° = -1270.2 kJ/mol-rxn

 

a. +48.6 kJ/mol-rxn
b. +179.0 kJ/mol-rxn
c. +345.5 kJ/mol-rxn
d. +441.0 kJ/mol-rxn
e. +1711.7 kJ/mol-rxn

 

 

ANS:  B

 

 

  1. Determine DrH° for the following reaction,

2 NH3(g) + 5/2 O2(g) ® 2 NO(g) + 3 H2O(g)

given the thermochemical equations below.

  N2(g) + O2(g) ® 2 NO(g) DrH° = +180.8 kJ/mol-rxn
  N2(g) + 3 H2(g) ® 2 NH3(g) DrH° = –91.8 kJ/mol-rxn
  2 H2(g) + O2(g) ® 2 H2O(g) DrH° = –483.6 kJ/mol-rxn

 

a. –1178.2 kJ/mol-rxn
b. –452.8 kJ/mol-rxn
c. –394.6 kJ/mol-rxn
d. –211.0 kJ/mol-rxn
e. +1178.2 kJ/mol-rxn

 

 

ANS:  B

 

  1. Determine the standard enthalpy of formation of calcium carbonate from the thermochemical equations given below.
  Ca(OH)2(s) ® CaO(s) + H2O() DrH° = 65.2 kJ/mol-rxn
  Ca(OH)2(s) + CO2(g) ® CaCO3(s) + H2O() DrH° = -113.8 kJ/mol-rxn
  C(s) + O2(g) ® CO2(g) DrH° = -393.5 kJ/mol-rxn
  2 Ca(s) + O2(g) ® 2 CaO(s) DrH° = -1270.2 kJ/mol-rxn

 

a. -1712.3 kJ/mol-rxn
b. -441.8 kJ/mol-rxn
c. -849.6 kJ/mol-rxn
d. -980.6 kJ/mol-rxn
e. -1207.6 kJ/mol-rxn

 

 

ANS:  E

 

  1. Which of the following reactions corresponds to the thermochemical equation for the standard molar enthalpy of formation of solid calcium nitrate?
a. Ca2+(aq) + 2NO3(aq) ® Ca(NO3)2(s)
b. Ca(OH)2(s) + 2HNO3(aq) ® Ca(NO3)2(s) + 2H2O()
c. Ca(s) + N2(g) + 3O2(g) ® Ca(NO3)2(s)
d. Ca(s) + 2HNO3(aq) ® Ca(NO3)2(s) + H2(g)
e. Ca(s) + 2N(g) + 6O(g) ® Ca(NO3)2(s)

 

 

ANS:  C

 

 

  1. Which of the following chemical equations does not correspond to a standard molar enthalpy of formation?
a. Mg(s) + C(s) + 3/2 O2(g) ® MgCO3(s)
b. C(s) + 1/2 O2(g) ® CO(g)
c. N2(g) + O2(g) ® 2 NO(g)
d. N2(g) + 2 O2(g) ® N2O4(g)
e. H2(g) + 1/2 O2(g) ® H2O()

 

 

ANS:  C

 

 

  1. What is the standard enthalpy of formation of BaCO3(s)?

BaO(s) + CO2(g)  ®  BaCO3(s); DH° = –269.3 kJ/mol-rxn

Substance DfH°(kJ/mol-rxn)
BaO(s) –553.5
CO2(g) –393.5

 

a. –109.3 kJ/mol-rxn
b. –429.3 kJ/mol-rxn
c. –677.7 kJ/mol-rxn
d. –1216.3 kJ/mol-rxn
e. 677.7 kJ/mol-rxn

 

 

ANS:  D

 

 

  1. Calculate DrH° for the combustion of ammonia,

4 NH3(g) + 7 O2(g) ® 4 NO2(g) + 6 H2O()

using standard molar enthalpies of formation.

 

  molecule DfH° (kJ/mol-rxn)
  NH3(g) –45.9
  NO2(g) +33.1
  H2O() –285.8

 

a. +30.24 kJ/mol-rxn
b. –206.9 kJ/mol-rxn
c. –298.6 kJ/mol-rxn
d. –1398.8 kJ/mol-rxn
e. –1663.6 kJ/mol-rxn

 

 

ANS:  D

 

  1. What is DrH° for the following phase change?

NaF(s) ® NaF(l)

Substance DH°f (kJ/mol-rxn)
NaF(s) –575.38
NaF(l) –546.20

 

a. 1121.58 kJ/mol-rxn
b. 29.18 kJ/mol-rxn
c. –1121.58 kJ/mol-rxn
d. –29.18 kJ/mol-rxn
e. 0 kJ/mol-rxn

 

 

ANS:  B

 

 

 

  1. The standard enthalpy change for the combustion of 1 mole of propane is –2043.0 kJ.

C3H8(g) + 5 O2(g) ® 3 CO2(g) + 4 H2O(g)

Calculate DfH° for propane based on the following standard molar enthalpies of formation.

 

  molecule DfH° (kJ/mol-rxn)
  CO2(g) –393.5
  H2O(g) –241.8

 

a. –1407.7 kJ/mol-rxn
b. +104.7 kJ/mol-rxn
c. –104.7 kJ/mol-rxn
d. –4190.7 kJ/mol-rxn
e. +1407.7 kJ/mol-rxn

 

 

ANS:  C

 

  1. The standard molar enthalpy of formation of NH3(g) is –45.9 kJ/mol. What is the enthalpy change if 9.51 g N2(g) and 1.96 g H2(g) react to produce NH3(g)?
a. –10.3 kJ/mol-rxn
b. –20.7 kJ/mol-rxn
c. –29.8 kJ/mol-rxn
d. –43.7 kJ/mol-rxn
e. –65.6 kJ/mol-rxn

 

 

ANS:  C

 

  1. When 1 mole of Fe2O3(s) reacts with H2(g) to form Fe(s) and H2O(g) according to the following equation, 98.8 kJ of energy are absorbed.

Fe2O3(s) + 3 H2(g)  ®  2 Fe(s) + 3 H2O(g)

 
(A)   (B)

Is the reaction endothermic or exothermic, and which of the enthalpy diagrams above

represents this reaction?

a. endothermic, A c. exothermic, A
b. endothermic, B d. exothermic, B

 

 

ANS:  B

 

SHORT ANSWER

 

  1. In thermodynamics, a(n) ________ is defined as the object, or collection of objects, being studied. The surroundings include everything else.

 

ANS:  system

 

 

  1. The heat required to convert a solid at its melting point to a liquid is called the heat of ________.

 

ANS:  fusion

 

 

  1. Dry ice converts directly from a solid to a gas when heated. This process is called ________.

 

ANS:  sublimation

 

 

  1. Why are you at greater risk from being burned by steam at 100 °C than from liquid water at the same temperature?

 

ANS:  At 100 °C, steam has approximately 40 kJ/mole more potential energy than liquid water at the same temperature.

 

  1. Internal energy and enthalpy are state functions. What is meant by this statement?

 

ANS:  In any process, the change in internal energy or the change in enthalpy is independent of the path between the two states. These values depend only on the initial and final states.

 

 

 

 

MULTIPLE CHOICE

 

  1. Which of the following statements is/are consistent with the Brønsted-Lowry concept of acids and bases?
  1. A conjugate acid-base pair may differ by only one proton.
  2. A Brønsted-Lowry base is defined as a hydroxide ion donor.
  3. Brønsted-Lowry acid-base reactions are restricted to aqueous solutions.

 

a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3

 

 

ANS:  A

 

  1. According to the Brønsted-Lowry definition, an acid
a. increases the H3O+ concentration in an aqueous solution.
b. is a strong electrolyte.
c. is a proton acceptor.
d. increases the pH of a solution.
e. is a proton donor.

 

 

ANS:  E

 

  1. Which of the following substances is never a Brønsted-Lowry acid in an aqueous solution?
a. sodium dihydrogen phosphate, NaH2PO4(s)
b. sodium acetate, NaCH3CO2(s)
c. ammonium nitrate, NH4NO3(s)
d. hydrogen bromide, HCl(g)
e. sodium bicarbonate, NaHCO3(s)

 

 

ANS:  B

 

 

  1. Which of the following substances is never a Brønsted-Lowry base in an aqueous solution?
a. potassium hydroxide, NaOH(g)
b. sodium hydrogen phosphate, Na2HPO4(s)
c. sodium phosphate, Na3PO4(s)
d. ammonium chloride, NH4Cl(g)
e. sodium bicarbonate, NaHCO3(s)

 

 

ANS:  D

 

 

  1. Which equation depicts aqueous hydrogen sulfide behaving as a Brønsted-Lowry acid in water?
a. H2S(aq) + 2 OH(aq)  SO2(aq) + 2 H2(g)
b. H2S(aq) + H3O+(aq)  H3S+(aq) + H2O()
c. H2S(aq) + H2O()  HS(aq) + H3O+(aq)
d. HS(aq) + H3O+(aq)  H2S(aq) + H2O()
e. H2S(aq) + H2O()  H3S++(aq) + OH(aq)

 

 

ANS:  C

 

 

 

  1. Which equation depicts hydrogen phosphate ion behaving as a Brønsted-Lowry acid in water?
a. HPO42–(aq) + H2O()  H2PO4(aq) + OH(aq)
b. HPO42–(aq) + OH(aq)  PO43–(aq) + H2O()
c. HPO42–(aq) + H2O()  PO43–(aq) + H3O+(aq)
d. 2 HPO42–(aq) + O2–(aq)  PO43–(aq) + H2O()
e. 2 HPO42–(aq) + H2O()  2 H2O() + P2O7(s)

 

 

ANS:  C

 

 

  1. Which of the following is the correct equation for the reaction of ammonia in water?
a. NH3(aq) + H2O(l)    NH4+(aq)  +  OH(aq)
b. NH3(aq)  +  H2O(l)    NH2(aq)  +  H3O+(aq)
c. NH3(aq)  +  H3O+(aq)    NH4+(aq)  +  H2O(l)
d. NH3(aq)  +  OH(aq)    NH2(aq)  +  H2O(l)
e. NH3(aq)  +  H2O(l)    NH2(aq)  +  H3O+(aq)

 

 

ANS:  A

 

 

  1. Which of the following equations shows that isoquinoline, C9H7N, behaves as a Brønsted-Lowry base in water?
a. C9H7N(aq)  +  H2O(l)   C9H7NH+(aq)  +  OH(aq)
b. C9H7N(aq)  +  H2O(l)    C9H6N(aq)  +  H3O+(aq)
c. C9H7N(aq)  +  OH(aq)    C9H6N(aq)  +  H2O(l)
d. C9H7N(aq)  +  H3O+(aq)    C9H7NH+(aq)  +  H2O(l)
e. C9H7NH+(aq)  +  H2O(l)    C9H7N(aq)  +  H3O+(aq)

 

 

ANS:  C

 

 

  1. In the following reaction,

HCO3(aq) + H2O()  CO32–(aq) + H3O+(aq)

a. H3O+ is an acid and HCO3 is its conjugate base.
b. HCO3 is an acid and CO32– is its conjugate base.
c. HCO3 is an acid and H2O is its conjugate base.
d. H2O is an acid and CO32– is its conjugate base.
e. H3O+ is an acid and CO32– is its conjugate base.

 

 

ANS:  B

 

 

  1. Which are the Brønsted–Lowry acids in the following equilibrium?

CH3COO(aq) + H2O(l)  CH3COOH(aq) + OH(aq)

a. CH3COO and OH
b. H2O and OH
c. H2O, CH3COOH, and OH
d. CH3COO and CH3COOH
e. H2O and CH3COOH

 

 

ANS:  E

 

 

 

  1. Which of the following pairs of species is not a conjugate acid–base pair?
a. HOCl, OCl
b. HNO2, NO2+
c. O2–, OH
d. HSO4, SO42–
e. H2CO3, HCO3

 

 

ANS:  B

 

 

  1. What is the conjugate base of [Fe(H2O)6]3+(aq)?
a. H3O+
b. [Fe(H2O)6]2+
c. [Fe(H2O)5H3O]4+
d. [Fe(H2O)5OH]2+
e. [Fe(H2O)5]3+

 

 

ANS:  D

 

 

  1. What is the conjugate base of HPO42- in aqueous solution?
a. not possible b. PO43– c. HPO42- d. H2PO4 e. H3PO4

 

 

ANS:  B

 

 

  1. Molecules or ions that can alternately behave as either a Brønsted-Lowry acid or base are called
a. polyanions.
b. hydronium ions.
c. polyprotic acids or bases.
d. conjugate acids or bases.
e. amphiprotic.

 

 

ANS:  E

 

 

  1. Which is NOT an amphiprotic species in water?
a. HClO3 b. HSO3 c. H3O+ d. HS e. HCO3

 

 

ANS:  A

 

 

  1. Which of the following species is amphiprotic in aqueous solution?
a. NH4+ b. H3O+ c. HCl d. CN e. H2O

 

 

ANS:  E

 

 

  1. At 50°C the autoionization constant for pure water, Kw, is . What is the H3O+ concentration in pure water at 50°C?
a.  M
b. 1.01 ´ 10-7 M
c.  M
d.  M
e. 1.01 ´ 10-14 M

 

 

ANS:  D

 

 

  1. The autoionization of pure water, as represented by the equation below, is known to be endothermic (DrH > 0).  Which of the following correctly states what occurs as the temperature of pure water is raised?

H2O(l) + H2O(l)  H3O+(aq) + OH(aq)      DrH > 0

a. Kw decreases, and the hydronium ion concentration decreases.
b. Kw decreases, and the hydronium ion concentration increases.
c. Kw and the hydronium ion concentration do not change.
d. Kw increases, and the hydronium ion concentration decreases.
e. Kw increases, and the hydronium ion concentration increases.

 

 

ANS:  E

 

  1. Which of the following expressions is not equivalent to pH?
a. –log [H+(aq)]
b.
c. 14.0 – pOH
d.
e. –log Kw

 

 

ANS:  E

 

  1. What volume of water must be added to 14.8 mL of a pH 2.0 solution of HNO3 in order to change the pH to 4.0?
a. 14.8 mL
b. 147 mL
c. 1.47 ´ 103 mL
d. 37 mL
e. 85 mL

 

 

ANS:  C

 

 

  1. What is the H3O+ concentration in 0.0047 M NaOH(aq) at 25 °C? (Kw = 1.01 ´ 10–14)
a. 2.1 ´ 10–12 M
b. 4.7 ´ 10–3 M
c. 1.0 ´ 10–14 M
d. 1.0 ´ 10–7 M
e. 4.7 ´ 10–17 M

 

 

ANS:  A

 

 

  1. Which one of the following aqueous solutions will have a pH of 2.00 at 25 °C? (Kw = 1.01 ´ 10–14)
a. 0.020 M HNO3
b. 2.0 M NaOH
c. 10.0 M HBr
d. 10.0 M KCl
e. 0.010 M HCl

 

 

ANS:  E

 

  1. What is the pH of a 0.016 M HClO4(aq) at 25 °C? (Kw = 1.01 ´ 10–14)
a. 15.80 b. 4.14 c. 12.20 d. 1.80 e. 9.86

 

 

ANS:  D

 

 

  1. The pH of a solution at 25°C in which [OH] = 3.9 ´ 10–5 M is ___.  (Kw = 1.01 ´ 10–14)
a. 4.41
b. 3.90
c. 9.59
d. 4.80
e. none of these

 

 

ANS:  C

 

 

  1. The H3O+ concentration of a solution is 2.5 ´ 10–6 M. What is the pH of the solution?
a. 6.81 b. 3.77 c. 2.00 d. 5.60 e. 10.60

 

 

ANS:  D

 

 

  1. What is the OH concentration of an aqueous solution with a pH of 2.77? (Kw = 1.01 ´ 10–14)
a. 5.9 ´ 10–12 M
b. 1.7 ´ 10–3 M
c. 5.2 ´ 10–2 M
d. 1.1 ´ 101 M
e. 5.9 ´ 102 M

 

 

ANS:  A

 

  1. What is the OH concentration of an aqueous solution with a pH of 9.83? (Kw = 1.01 ´ 10–14)
a. 1.3 ´ 10–10 M
b. 6.8 ´ 10–5 M
c. 6.8 ´ 10–1 M
d. 1.5 ´ 10–2 M
e. 7.4 ´ 109 M

 

 

ANS:  B

 

  1. What is the pH of the final solution when 25 mL of 0.021 M HCl has been added to 35 mL of 0.036 M HCl at 25°C?
a. 3.3 b. 1.9 c. 1.5 d. 2.7 e. 3.5

 

 

ANS:  C

 

 

  1. An aqueous solution with a pH of 10.60 is diluted from 1.0 L to 2.0 L. What is the pH of the diluted solution?
a. 5.30 b. 9.60 c. 10.30 d. 10.60 e. 10.90

 

 

ANS:  C

 

 

  1. What is the H3O+ concentration of 0.0017 M NaOH(aq) at 25 °C? (Kw = 1.01 ´ 10–14)
a. 5.9 ´ 10–12 M
b. 1.7 ´ 10–3 M
c. 1.0 ´ 10–14 M
d. 1.0 ´ 10–7 M
e. 1.7 ´ 10–17 M

 

 

ANS:  A

 

 

  1. What is the hydronium-ion concentration in a solution formed by combining 750 mL of 0.10 M NaOH with 250 mL of 0.30 M HCl?

NaOH(aq) + HCl(aq) ® NaCl(aq) + H2O(l)

a. 0.075 M
b. 1.7 ´ 10–13 M
c. 1.0 ´ 10–7 M
d. 0.30 M
e. 0.10 M

 

 

ANS:  C

 

 

  1. The concentration of H3O+ in a solution is 7 ´ 10–4 M at 25°C. What is its hydroxide-ion concentration? (Kw = 1.01 ´ 10–14)
a. 7 ´ 10–4 M
b. 1 ´ 10–10 M
c. 2 ´ 10–10 M
d. 3 ´ 10–10 M
e. 1 ´ 10–11 M

 

 

ANS:  E

 

 

  1. What is the H3O+ concentration in 0.0042 M Ba(OH)2(aq) at 25 °C? (Kw = 1.01 ´ 10–14)?
a. 8.4 ´ 10–3 M
b. 4.2 ´ 10–3 M
c. 1.2 ´ 10–12 M
d. 2.4 ´ 10–12 M
e. 1.0 ´ 10–7 M

 

 

ANS:  C

 

 

  1. A solution has a hydroxide-ion concentration of 0.0030 M. What is the pOH of the solution at 25 °C? (Kw = 1.01 ´ 10–14)
a. 11.48 b. 2.52 c. 7.00 d. 8.19 e. 5.81

 

 

ANS:  B

 

 

  1. What is the pOH of 0.067 M HI(aq) at 25 °C? (Kw = 1.01 ´ 10–14)?
a. 2.70 b. 12.83 c. 11.30 d. 15.17 e. 1.17

 

 

ANS:  B

 

 

 

  1. What is the pH of a solution prepared by dissolving 0.923 g of NaOH(s) in 5.50 L of water? (Kw = 1.01 ´ 10–14)
a. 1.637 b. 12.363 c. 7.000 d. 11.623 e. 2.377

 

 

ANS:  D

 

 

  1. What is the pH of a solution prepared by dissolving 0.581 L of HCl(g), measured at STP, in enough water such that the total volume of the solution is 2.00 L?  (R = 0.0821 L · atm/K·mol)
a. 1.887 b. 12.113 c. 1.586 d. 7.000 e. 12.414

 

 

ANS:  A

 

 

  1. What is the hydroxide-ion concentration in a solution formed by combining 200. mL of 0.15 M HCl with 300. mL of 0.091 M NaOH at 25°C?

HCl(aq) + NaOH(aq) ® NaCl(aq) + H2O(l)

a. 1.7 ´ 10–13 M
b. 0.091 M
c. 1.9 ´ 10–12 M
d. 0.055 M
e. 1.0 ´ 10–7 M

 

 

ANS:  C

 

 

  1. Hydrofluoric acid has a pKa value of 3.14. What is the value of pKb for fluoride ion?
a. 1.4 ´ 10–11 b. 7.2 ´ 10–4 c. 3.14 d. 10.86 e. 17.14

 

 

ANS:  D

 

  1. Consider the reaction CO32-(aq) + H2O(l)  HCO3(aq) + OH(aq). Kb for CO32- is 2.1 ´ 10–4 at 25°C. What is Ka for the HCO3 ion at 25°C?
a. 4.8 ´ 103 b. 4.8 ´ 10–11 c. 2.1 ´ 10–4 d. 7.2 ´ 10–12 e. 9.2 ´ 10–8

 

 

ANS:  B

 

 

  1. What is Ka at 25°C for the following equilibrium given Kb (CH3NH2) = 4.4 ´ 10–4 at 25°C.?

CH3NH3+(aq) + H2O(l)  CH3NH2(aq) + H3O+(aq)

a. 4.4 ´ 10–4 b. 2.3 ´ 103 c. 4.4 ´ 10–10 d. 4.4 ´ 104 e. 2.3 ´ 10–11

 

 

ANS:  E

 

 

 

  1. Consider the Ka values for the following acids:

Cyanic acid, HOCN, 3.5 ´ 10–4

Formic acid, HCHO2, 1.7 ´ 10–4

Lactic acid, HC3H5O3, 1.3 ´ 10–4

Propionic acid, HC3H5O2, 1.3 ´ 10–5

Benzoic acid, HC7H5O2, 6.3 ´ 10–5

Which has the strongest conjugate base?

a. HOCN b. HCHO2 c. HC3H5O3 d. HC3H5O2 e. HC7H5O2

 

 

ANS:  D

 

 

  1. Consider the Ka values for the following acids:

Cyanic acid, HOCN, 3.5 ´ 10–4

Formic acid, HCHO2, 1.7 ´ 10–4

Lactic acid, HC3H5O3, 1.3 ´ 10–4

Propionic acid, HC3H5O2, 1.3 ´ 10–5

Benzoic acid, HC7H5O2, 6.3 ´ 10–5

Given initially equimolar solutions of each weak acid, which solution will have the highest pH once equilibrium is established?

a. HOCN b. HC7H5O2 c. HC3H5O2 d. HC3H5O3 e. HCHO2

 

 

ANS:  C

 

 

  1. H3PO3 is a diprotic weak acid.  What is the balanced equilibrium defined as Kb2 of H3PO3?
a. H3PO3(aq) + H2O(l)  H3O+(aq) + H2PO3(aq)
b. H2PO3(aq) + H2O(l)  H3O+(aq) + HPO32–(aq)
c. HPO32–(aq) + H2O(l)  OH(l) + H2PO3(aq)
d. H2PO3(aq) + H2O(l)  OH(l) + H3PO3(aq)
e. HPO32–(aq) + H2O(l)  OH(aq) + H3PO3(aq)

 

 

ANS:  D

| 16.8 Polyprotic Acids and Bases

 

 

  1. The Ka for the monoprotic acid hypochlorous acid is 3.5 ´ 10–8.  What is Kb for the hypochlorite ion, the conjugate base of hypochlorous acid?
a. 2.9 ´ 10–7 b. 3.5 ´ 10–8 c. 2.9 ´ 107 d. 3.5 ´ 106 e. 3.5 ´ 10–22

 

 

ANS:  A

 

 

  1. Given that Ka for the weak acid HA is 3.46 ´ 10–8, calculate K for the reaction of HA with OH.

 

HA(aq) + OH(aq)  A(aq) + H2O()

 

a. 3.46 b. 3.46 ´ 106 c. 3.46 ´ 10–22 d. 2.89 ´ 1021 e. 2.89 ´ 10–7

 

 

ANS:  B

 

 

  1. At 25 °C, all of the following ionic compounds produce a basic aqueous solution, except ____.
a. KSH b. Na3PO4 c. LiNO2 d. KHSO3 e. KCH3CO2

 

 

ANS:  D

 

 

  1. At 25 °C, all of the following ions produce an acidic solution, except ____.
a. NH4+ b. HSO3 c. HPO42– d. [Fe(H2O)6]3+ e. [Al(H2O)6]3+

 

 

ANS:  C

 

  1. Which ionic compound forms a pH-neutral aqueous solution at 25 °C?
a. KHCO3 b. LiCl c. KOCl d. NH4Cl e. K2S

 

 

ANS:  B

 

 

  1. What is the equilibrium constant for the following reaction,

HCO2H(aq) + CN(aq)  HCO2(aq) + HCN(aq)

and does the reaction favor the formation of reactants or products? The acid dissociation constant, Ka, for HCO2H is 1.8 ´ 10–4 and the acid dissociation constant for HCN is 4.0 ´ 10–10.

a. K = 1.00. The reaction favors neither the formation of reactants nor products.
b. K = 2.2 ´ 10–6. The reaction favors the formation of products.
c. K = 2.2 ´ 10–6. The reaction favors the formation of reactants.
d. K = 4.5 ´ 105. The reaction favors the formation of products.
e. K = 4.5 ´ 105. The reaction favors the formation of reactants.

 

 

ANS:  D

 

 

  1. Aqueous solutions of ammonia (NH3) and hydrogen cyanide (HCN) react to produce ammonium cyanide, (NH4CN) according to the following equilibrium reaction.

NH3(aq) + HCN(aq) D NH4+(aq) + CN(aq)

Given the following equilibrium constants, which statement best describes the reaction once equilibrium is established?  (Kw = 1.01 ´ 10-14)

 

NH4+ Ka = 5.6 ´ 10-10
HCN Ka = 4.0 ´ 10-10

   

a. The reaction is product favored.
b. The reaction is reactant favored.
c. The reaction is neither product nor reactant favored.

 

 

ANS:  B

 

 

  1. Given the following equilibrium constants,

Ka (HSO4) = 1.2 ´ 10–2

Kb (CH3CO2) = 5.6 ´ 10–10

Kw = 1.00 ´ 10–14

determine the equilibrium constant for the reaction below at 25 °C.

HSO4(aq) + CH3CO2(aq)  SO42–(aq) + CH3CO2H(aq)

a. 6.7 ´ 10–12 b. 2.1 ´ 10–7 c. 1.5 ´ 10–3 d. 6.7 ´ 102 e. 2.1 ´ 107

 

 

ANS:  D

 

 

  1. Given the following acid dissociation constants,

Ka (H3PO4) = 7.5 ´ 10–3

Ka (NH4+) = 5.6 ´ 10–10

determine the equilibrium constant for the reaction below at 25 °C.

H3PO4(aq) + NH3(aq)  NH4+(aq) + H2PO4(aq)

a. 4.2 ´ 10–12 b. 7.5 ´ 10–8 c. 4.2 ´ 102 d. 1.3 ´ 107 e. 2.4 ´ 1011

 

 

ANS:  D

 

 

  1. Given the equilibrium constants for the equilibria,

NH4+(aq) + H2O(l)  NH3(aq) + H3O+(aq); K =

2CH3COOH(aq) + 2H2O(l)  2CH3COO(aq) + 2H3O+(aq); K =

determine Kc for the following equilibrium.

CH3COOH(aq) + NH3(aq)   CH3COO(aq) + NH4+(aq)

a. 3.08 ´ 104 b. 3.25 ´ 10-5 c. 9.96 ´ 10-15 d. 1.00 ´ 1014 e. 1.75 ´ 10-5

 

 

ANS:  A

 

 

  1. The complete reaction of an acid and base is as follows.

HClO4(aq) + LiOH(aq) ® H2O() + LiClO4(aq)

What is the equilibrium constant for the net ionic reaction at 25 °C?

a. 1.01 ´ 10–14
b. 1.01 ´ 10–7
c. 1.01 ´ 107
d. 1.01 ´ 1014
e. more information required

 

 

ANS:  D

 

 

  1. Which acid-base reaction results in an acidic solution?
a. HNO3(aq) + CsOH(aq) ® H2O() + CsNO3(aq)
b. HI(aq) + LiOH(aq) ® H2O() + LiI(aq)
c. HBr(aq) + NaOH(aq) ® H2O() + NaBr(aq)
d. H2SO3(aq) + LiOH(aq)  H2O() + LiHSO3(aq)
e. HF(aq) + LiOH(aq)  H2O() + LiF(aq)

 

 

ANS:  D

 

 

  1. What is the hydronium-ion concentration of a 0.25 M solution of HCN (Ka = 4.9 ´ 10–10) at 25°C?
a. 1.6 ´ 10–4 M b. 3.3 ´ 10–6 M c. 2.1 ´ 10–6 M d. 1.1 ´ 10–5 M e. 4.4 ´ 10–5 M

 

 

ANS:  D

 

 

  1. What is the equilibrium pH of an initially 0.64 M solution of the monoprotic acid benzoic acid at 25°C (Ka = )?
a. 2.20 b. 7.00 c. 1.90 d. 12.10 e. 5.10

 

 

ANS:  A

 

 

  1. What is the equilibrium hydronium ion concentration of an initially 5.4 M solution of hypochlorous acid, HOCl, at 25°C (Ka = )?
a.  M b.  M c.  M d.  M e.  M

 

 

ANS:  A

 

 

  1. What is the OH concentration in 0.48 M CH3CO2(aq)? (Kb of CH3CO2 = 5.6 ´ 10–10)
a. 2.7 ´ 10–10 M
b. 6.2 ´ 10–10 M
c. 1.1 ´ 10–5 M
d. 1.6 ´ 10–5 M
e. 2.4 ´ 10–5 M

 

 

ANS:  D

 

  1. What is the pH of a 0.28 M solution of sodium propionate, NaC3H5O2, at 25°C? (propionic acid, HC3H5O2, is monoprotic and has a Ka = 1.3 ´ 10–5 at 25°C..  Kw = 1.01 ´ 10-14 )
a. 6.26 b. 4.83 c. 11.10 d. 7.74 e. 9.17

 

 

ANS:  E

 

 

  1. What is the pH of a 0.11 M solution of methylamine (CH3NH2, Kb = 4.4 ´ 10–4) at 25oC? (Kw = 1.01 ´ 10-14)
a. 5.80 b. 0.96 c. 11.83 d. 13.04 e. 2.17

 

 

ANS:  C

 

 

  1. What is the pH of 0.010 M aqueous hypochlorous acid? (Ka of HOCl = 3.5 ´ 10–8)
a. 2.00
b. 4.50
c. 4.73
d. 6.54
e. 7.45

 

 

ANS:  C

 

  1. The pH of aqueous 0.10 M pyridine (C5H5N) ion is 9.09. What is the Kb of this base?
a. 8.0 ´ 10–10
b. 1.5 ´ 10–9
c. 9.0 ´ 10–6
d. 1.6 ´ 10–5
e. 1.2 ´ 10–5

 

 

ANS:  B

 

  1. A 0.10 M solution of a weak monoprotic acid has a hydronium-ion concentration of 4.6 ´ 10–4 M. What is the acid-ionization constant, Ka, for this acid?
a. 2.1 ´ 10–2 b. 3.2 ´ 10–3 c. 4.6 ´ 10–4 d. 2.1 ´ 10–6 e. 5.5 ´ 10–5

 

 

ANS:  D

 

 

  1. What is the equilibrium pOH of an initially 5.4 M solution of hypochlorous acid, HOCl, at 25°C (Ka = ; Kw = 1.01 ´ 10-14)?
a. 10.60 b. 7.42 c. 10.45 d. 10.76 e. 4.13

 

 

ANS:  A

 

 

  1. What is the pH of the solution which results from mixing 50.0 mL of 0.30 M HF(aq) and 50.0 mL of 0.30 M NaOH(aq) at 25 °C? (Ka of HF = 7.2 ´ 10–4)
a. 1.98 b. 5.84 c. 8.16 d. 10.85 e. 12.02

 

 

ANS:  C

 

  1. What is the pH of the solution which results from mixing 75 mL of 0.50 M NH3(aq) and 75 mL of 0.50 HCl(aq) at 25 °C? (Kb for NH3 = 1.8 ´ 10–5)
a. 0.60 b. 2.67 c. 4.74 d. 4.93 e. 9.26

 

 

ANS:  D

 

  1. Carbonic acid is a diprotic acid, H2CO3, with Ka1 = 4.2 ´ 10–7 and Ka2 = 4.8 ´ 10–11 at 25°C. The ion product for water is Kw = 1.0 ´ 10–14 at 25°C. What is the OH concentration of a solution that is 0.18 M in Na2CO3?
a. 6.1 ´ 10–3 M b. 2.1 ´ 10–4 M c. 6.5 ´ 10–5 M d. 2.9 ´ 10–6 M e. 2.7 ´ 10–4 M

 

 

ANS:  A

 

 

  1. What is the equilibrium pH of a 0.835 M solution of H3PO4(aq)? (Ka1 = 7.5 ´ 10–3, Ka2 = 6.2 ´ 10–8, Ka3 = 4.8 ´ 10–13)
a. 1.12 b. 3.64 c. 12.32 d. 6.20 e. 7.21

 

 

ANS:  A

 

 

  1. Calculate the pH of a 0.04 M solution of ascorbic acid (Ka1 = 7.9 ´ 10–5; Ka2 is 1.6 ´ 10–12).
a. 11.2 b. 2.8 c. 5.5 d. 8.5 e. 11.8

 

 

ANS:  B

 

 

  1. The pH of a solution of 2.2 M H2A (Ka1 = 1.0 ´ 10–6 and Ka2 is 1.0 ´ 10–10) is:
a. 10.00 b. 2.83 c. 11.17 d. 5.66 e. 7.00

 

 

ANS:  B

 

 

  1. Calculate the pH of the following aqueous solution:

0.29 M H2S (pKa1 = 7.00; pKa2 = 12.89)

a. 10.23 b. 6.46 c. 3.77 d. 7.54 e. 7.00

 

 

ANS:  C

 

 

  1. What is the hydroxide-ion concentration in a 0.22 M solution of Na2CO3?   For carbonic acid, Ka1 = 4.2 ´ 10–7 and Ka2 = 4.8 ´ 10–11.  (Kw = 1.0 ´ 10–14)
a. 6.8 ´ 10–3 M b. 2.0 ´ 10–4 M c. 7.2 ´ 10–5 M d. 4.2 ´ 10–9 M e. 3.2 ´ 10–6 M

 

 

ANS:  A

 

 

  1. What is the equilibrium concentration of H2C2O4 in a 0.230 M oxalic acid, H2C2O4, solution?  For oxalic acid, Ka1 = 5.6 ´ 10–2 and Ka2 = 5.1 ´ 10–5.
a. 1.4 ´ 10–1 M b. 1.1 ´ 10–1 M c. 2.3 ´ 10–1 M d. 5.1 ´ 10–5 M e. 8.9 ´ 10–2 M

 

 

ANS:  A

 

 

  1. What is the hydroxide-ion concentration of a 0.250 M sodium oxalate (Na2C2O4) solution?  For oxalic acid (H2C2O4), Ka1 = 5.6 ´ 10–2 and Ka2 = 5.1 ´ 10–5.  (Kw = 1.01 ´ 10-14)
a. 7.0 ´ 10–6 M b. 1.0 ´ 10–7 M c. 9.4 ´ 10–2 M d. 3.5 ´ 10–3 M e. 2.1 ´ 10–7 M

 

 

ANS:  A

 

 

  1. Which of the following species is the strongest acid in an aqueous solution?
a. CH3CH2CO2H
b. CH2ClCO2H
c. CH3CO2H
d. CCl3CO2H
e. CHCl2CO2H

 

 

ANS:  D

 

 

  1. Which of the following statements is INCORRECT?
a. H3PO4 is a stronger acid than H2PO4.
b. HClO3 is a stronger acid than HClO2.
c. HNO3 is a stronger acid than HNO2.
d. [Fe(H2O)6]2+ is a stronger acid than [Fe(H2O)6]3+.
e. HOCl is stronger acid than HOBr.

 

 

ANS:  D

 

 

  1. Rank the following in order of decreasing acid strength in aqueous solution: HCl, HOCl, HOBr, HOI.
a. HCl > HClO > HBrO > HIO
b. HIO > HBrO > HClO > HCl
c. HCl > HIO > HBrO > HClO
d. HClO > HCl > HBrO > HIO
e. HClO > HBrO > HCl > HIO

 

 

ANS:  A

 

 

 

  1. All of the following compounds are acids containing chlorine. Which compound is the weakest acid?
a. HCl b. HClO c. HClO2 d. HClO3 e. HClO4

 

 

ANS:  B

 

 

  1. Which of the following molecules or ions is the strongest acid?
a. CH3CO2 b. CH3CO2H c. CFH2CO2H d. CF2HCO2H e. CF3CO2H

 

 

ANS:  E

 

 

 

  1. Which of the following is the strongest acid in aqueous solution?
a. H3AsO4 b. H3PO4 c. H3PO3 d. H3SbO4 e. H3AsO3

 

 

ANS:  B

 

 

  1. Rank H3PO4, H2PO4, and HPO42– in order of increasing acid strength.
a. HPO42– < H2PO4 < H3PO4
b. H2PO4 < HPO42– < H3PO4
c. H2PO4 < H3PO4 < HPO42–
d. HPO42– < H3PO4 < H2PO4
e. H3PO4 < H2PO4 < HPO42–

 

 

ANS:  A

 

 

  1. Identify from the following list of molecules and ions which behave as Lewis acids: CO2, NH3, BCl3, Fe3+.
a. CO2 and NH3
b. NH3 and BCl3
c. CO2 and Fe3+
d. CO2, BCl3, and Fe3+
e. CO2, NH3, BCl3, and Fe3+

 

 

ANS:  D

 

  1. All of the following species behave as Lewis acids EXCEPT ____.
a. BH3 b. Al3+ c. SO2 d. Al(OH)3 e. NH3

 

 

ANS:  E

 

  1. In the reaction

CuO(s) + CO2(g) ® CuCO3(s),

a. O2– acts as a Lewis base and CO2 acts as a Lewis acid.
b. O2– acts as a Lewis base and Cu2+ acts as a Lewis acid.
c. CuO is the Lewis acid and CuCO3 is its conjugate base.
d. CO2 is the Lewis acid and CuCO3 is its conjugate base.
e. Cu2+ acts as a Lewis acid and CO32– acts as a Lewis base.

 

 

ANS:  A

 

 

  1. Which of the following species cannot act as a Lewis base?
a. S2– b. H2S c. NH3 d. CH4 e. SH

 

 

ANS:  D

 

 

SHORT ANSWER

 

  1. When a Lewis acid and a Lewis base combine, the product may be referred to as an acid-base ________.

 

ANS:  adduct (or complex)

 

 

 

  1. A molecule that can behave as either a Brønsted-Lowry acid or base is termed ________.

 

ANS:  amphiprotic (or amphoteric)

 

  1. When a Lewis acid combines with a Lewis base, the base supplies both electrons to the bond. This type of chemical bond is called a(n) ________ covalent bond.

 

ANS:  coordinate

 

 

  1. The chemical equations below show the reaction of Al(OH)3 as a Lewis acid and as a Lewis base, respectively.

Al(OH)3(s) + OH(aq)  Al(OH)4(aq)

Al(OH)3(s) + 3 H3O+(aq)  Al3+(aq) + 3 H2O()

Substances that can behave as either Lewis acids or bases are called ________ substances.

 

ANS:  amphoteric

 

 

  1. Write a net ionic equation for the neutralization reaction of hydrochloric acid and potassium hydroxide. Identify the spectator ion(s).

 

ANS:  Net ionic equation: H3O+(aq) + OH(aq)  2 H2O(); spectator ions: Cl and K+.

 

  1. Which is the stronger Brønsted-Lowry acid, Fe(H2O)62+ or Fe(H2O)63+? Explain.

 

ANS:  Fe(H2O)63+. When a proton dissociates from the oxygen atom, the oxygen is left with an extra electron. This negative charge is stabilized by the interaction of the oxygen with the iron cation. Since the Fe3+ is more positively charged than the Fe2+, it can more effectively stabilize the negative charge.

 

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