Question 1

Which of the following chemical equations does not correspond to a standard molar enthalpy of formation?

Accepted Answer

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(   ) 
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(   ) C

Question 2

Exactly 149.6 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?

Accepted Answer

A)  0.427 J/(g · °
C)  
B)  2.34 J/(g · °
C)  
C)  20.6 J/(g · °
C)  
D)  35.8 J/(g · °
C)  
E)  None of these 
A)  0.427 J/(g · °
C)  
B)  2.34 J/(g · °
C)  
C)  20.6 J/(g · °
C)  
D)  35.8 J/(g · °
C)  
E)  None of these A

Question 3

A bomb calorimeter has a heat capacity of 2.47 kJ/K.When a 0.103-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.

Accepted Answer

A)  -5.29 J/g 
B)    J/g 
C)  -0.120 J/g 
D)    J/g 
E)  -0.540 J/g 
A)  -5.29 J/g 
B)    J/g 
C)  -0.120 J/g 
D)    J/g 
E)  -0.540 J/g B

Question 4

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

Accepted Answer

The answer of The heat required to convert a solid...

Question 5

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?

Accepted Answer

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 
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

Question 6

The following reaction of iron oxide with aluminum is an exothermic reaction. Fe2O3(s)+ 2 Al(s)→ 2 Fe(s)+ Al2O3(s)
The reaction of 5.00 g of Fe2O3 with excess Al(s)evolves 26.6 kJ of energy in the form of heat.Calculate the enthalpy change per mole of Fe2O3.

Accepted Answer

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 
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

Question 7

The thermochemical equation for the combustion of methanol is given below. CH3OH(   )+ 3/2 O2(g)→ CO2(g)+ 2 H 2O(g)
ΔrH° = -638.7 kJ/mol-rxn
What is the enthalpy change for the combustion of 8.59 g of CH3OH?

Accepted Answer

A)  -171 kJ 
B)  -19.9 kJ 
C)  -2.38 × 103 kJ 
D)  -5.49 × 103 kJ 
E)  -1.76 × 106 kJ 
A)  -171 kJ 
B)  -19.9 kJ 
C)  -2.38 × 103 kJ 
D)  -5.49 × 103 kJ 
E)  -1.76 × 106 kJ

Question 8

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

Accepted Answer

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 
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

Question 9

Heat capacity is defined as

Accepted Answer

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. 
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.

Question 10

Which of these physical changes would require the release of energy?

Accepted Answer

A)  freezing a liquid 
B)  boiling a liquid 
C)  melting a solid 
D)  all of these 
E)  none of these 
A)  freezing a liquid 
B)  boiling a liquid 
C)  melting a solid 
D)  all of these 
E)  none of these

Question 11

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)

Accepted Answer

A)  -0.6 °C 
B)  5.5 °C 
C)  12.1 °C 
D)  17.6 °C 
E)  38.9 °C 
A)  -0.6 °C 
B)  5.5 °C 
C)  12.1 °C 
D)  17.6 °C 
E)  38.9 °C

Question 12

Determine the heat of evaporation of carbon disulfide, CS2(   )→ CS2(g)
Given the enthalpies of reaction below.
C(s)+ 2 S(s)→ CS2(   )
ΔrH° = +89.4 kJ/mol-rxn
C(s)+ 2 S(s)→ CS2(g)
ΔrH° = +116.7 kJ/mol-rxn

Accepted Answer

A)  -206.1 kJ 
B)  -27.3 kJ 
C)  +27.3 kJ 
D)  +206.1 kJ 
E)  +1.31 kJ 
A)  -206.1 kJ 
B)  -27.3 kJ 
C)  +27.3 kJ 
D)  +206.1 kJ 
E)  +1.31 kJ

Question 13

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.

Accepted Answer

A)  25.1 °C 
B)  45.4 °C 
C)  50.8 °C 
D)  64.8 °C 
E)  48.9 °C 
A)  25.1 °C 
B)  45.4 °C 
C)  50.8 °C 
D)  64.8 °C 
E)  48.9 °C

Question 14

Which of the following is an endothermic process?

Accepted Answer

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 
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

Question 15

In a reaction,the values of ∆H and ∆U are always the same irrespective of the path taken to reach the products from reactants.

Accepted Answer

A) True 
 B)False

Question 16

How much energy is gained by copper when 68.4 g of copper is warmed from 13.4 °C to 78.4 °C? The specific heat capacity of copper is 0.385 J/(g·°C).

Accepted Answer

A)  3.53 × 102 J 
B)  30.18 J 
C)  25.02 J 
D)  1.71 × 103 J 
E)  2.06 × 103 J 
A)  3.53 × 102 J 
B)  30.18 J 
C)  25.02 J 
D)  1.71 × 103 J 
E)  2.06 × 103 J

Question 17

If 46.1 g of copper at 11.6 °C is placed in 85.0 g of water 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.

Accepted Answer

A)  71.2 °C 
B)  63.6 °C 
C)  51.0 °C 
D)  42.0 °C 
E)  69.5 °C 
A)  71.2 °C 
B)  63.6 °C 
C)  51.0 °C 
D)  42.0 °C 
E)  69.5 °C

Question 18

One statement of the first law of thermodynamics is that

Accepted Answer

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. 
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.

Question 19

If q = 39 kJ and w = -74 kJ for a certain process,it most likely _____.

Accepted Answer

A)  requires a catalyst 
B)  is endothermic 
C)  occurs slowly 
D)  is exothermic 
E)  cannot occur 
A)  requires a catalyst 
B)  is endothermic 
C)  occurs slowly 
D)  is exothermic 
E)  cannot occur

Question 20

Which of the following thermodynamic quantities are state functions: heat (q),work (w),enthalpy change (ΔH),and/or internal energy change (ΔU)?

Accepted Answer

A)  q only 
B)  w only 
C)  ΔH only 
D)  ΔU only 
E)  ΔH and ΔU 
A)  q only 
B)  w only 
C)  ΔH only 
D)  ΔU only 
E)  ΔH and ΔU

Exam 6: Principles of Chemical Reactivity: Energy and Chemical Reactions

Which of the following chemical equations does not correspond to a standard molar enthalpy of formation?

Exactly 149.6 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 bomb calorimeter has a heat capacity of 2.47 kJ/K.When a 0.103-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.

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

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?

The following reaction of iron oxide with aluminum is an exothermic reaction. Fe2O3(s)+ 2 Al(s)→ 2 Fe(s)+ Al2O3(s) The reaction of 5.00 g of Fe2O3 with excess Al(s)evolves 26.6 kJ of energy in the form of heat.Calculate the enthalpy change per mole of Fe2O3.

The thermochemical equation for the combustion of methanol is given below. CH3OH( )+ 3/2 O2(g)→ CO2(g)+ 2 H 2O(g) ΔrH° = -638.7 kJ/mol-rxn What is the enthalpy change for the combustion of 8.59 g of CH3OH?

Heat capacity is defined as

Which of these physical changes would require the release of energy?

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)

Determine the heat of evaporation of carbon disulfide, CS2( )→ CS2(g) Given the enthalpies of reaction below. C(s)+ 2 S(s)→ CS2( ) ΔrH° = +89.4 kJ/mol-rxn C(s)+ 2 S(s)→ CS2(g) ΔrH° = +116.7 kJ/mol-rxn

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.

Which of the following is an endothermic process?

In a reaction,the values of ∆H and ∆U are always the same irrespective of the path taken to reach the products from reactants.

How much energy is gained by copper when 68.4 g of copper is warmed from 13.4 °C to 78.4 °C? The specific heat capacity of copper is 0.385 J/(g·°C).

If 46.1 g of copper at 11.6 °C is placed in 85.0 g of water 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.

One statement of the first law of thermodynamics is that

If q = 39 kJ and w = -74 kJ for a certain process,it most likely _____.

Which of the following thermodynamic quantities are state functions: heat (q),work (w),enthalpy change (ΔH),and/or internal energy change (ΔU)?

Basic Concepts of Chemistry

Lets Review: The Tools of Quantitative Chemistry

Atoms, molecules, and Ions

Chemical Reactions

Stoichiometry: Quantitative Information About Chemical Reactions

The Structure of Atoms

The Structure of Atoms and Periodic Trends

Bonding and Molecular Structure

Bonding and Molecular Structure Orbital Hybridization and Molecular Orbitals

Gases and Their Properties

Intermolecular Forces and Liquids

The Solid State

Solutions and Their Behavior

Chemical Kinetics: the Rates of Chemical Reactions

Principles of Chemical Reactivity: Equilibria

Principles of Chemical Reactivity: the Chemistry of Acids and Bases

Principles of Chemical Reactivity: Other Aspects of Aqueous Equilibria

Principles of Chemical Reactivity: Entropy and Free Energy

Principles of Chemical Reactivity: Electron Transfer Reactions

Environmental Chemistry: Earths Environment, energy, and Sustainability

The Chemistry of the Main Group Elements

The Chemistry of the Transition Elements

Carbon: Not Just Another Element

Biochemistry

Nuclear Chemistry

Filters

The following reaction of iron oxide with aluminum is an exothermic reaction. Fe₂O₃(s)+ 2 Al(s)→ 2 Fe(s)+ Al₂O₃(s) The reaction of 5.00 g of Fe₂O₃ with excess Al(s)evolves 26.6 kJ of energy in the form of heat.Calculate the enthalpy change per mole of Fe₂O₃.

The thermochemical equation for the combustion of methanol is given below. CH₃OH( )+ 3/2 O₂(g)→ CO₂(g)+ 2 H ₂O(g) Δ_rH° = -638.7 kJ/mol-rxn What is the enthalpy change for the combustion of 8.59 g of CH₃OH?

Determine the heat of evaporation of carbon disulfide, CS₂( )→ CS₂(g) Given the enthalpies of reaction below. C(s)+ 2 S(s)→ CS₂( ) Δ_rH° = +89.4 kJ/mol-rxn C(s)+ 2 S(s)→ CS₂(g) Δ_rH° = +116.7 kJ/mol-rxn

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.