Question 1

The observation that at equilibrium, the reaction quotient equals the equilibrium constant, is representative of which law?

Accepted Answer

A)  Law of equal states 
B)  Reversibility law 
C)  Law of equivalence 
D)  Law of reactant-product equivalence 
E)  Law of mass action 
A)  Law of equal states 
B)  Reversibility law 
C)  Law of equivalence 
D)  Law of reactant-product equivalence 
E)  Law of mass action

Question 2

Hydrogen peroxide (H2O2) decomposes according to the following equation. H2O2(l) → H2O(l) + ½O2(g).
What is KP for this reaction at 25°C? (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K • mol, R = 8.314 J/K • mol)

Accepted Answer

A)  1.3 × 10-21 
B)  20.9 
C)  3.46 × 1017 
D)  7.4 × 1020 
E)  8.6 × 104 
A)  1.3 × 10-21 
B)  20.9 
C)  3.46 × 1017 
D)  7.4 × 1020 
E)  8.6 × 104

Question 3

Increasing the temperature of an exothermic reaction causes the equilibrium constant to increase and shifts the equilibrium toward products.

Accepted Answer

A) True 
 B)False

Question 4

The equilibrium constant expression for the reaction
CuO(s) + H2(g)   Cu(s) + H2O(g) is Kc = [H2]/[H2O].

Accepted Answer

A) True 
 B)False

Question 5

Consider the equilibrium equation C(s) + O2(g)   CO2(g), where ΔHrxn = -393.5 kJ/mol.
The reaction will shift toward the ________ if the temperature of the system is decreased.

Accepted Answer

Question 6

Consider the chemical reaction 2NH3(g)   N2(g) + 3H2(g). The equilibrium is to be established in a 1.0-L container at 1000 K, where Kc = 4.0 × 10-2. Initially, 1.22 moles of NH3(g) are present. What is the equilibrium concentration of H2(g)?

Accepted Answer

Question 7

Consider the reversible reaction: 2NO2(g)   N2O4(g) If the concentrations of both NO2 and N2O4 are each 0.016 M, what is the value of Qc?

Accepted Answer

A)  0.016 
B)  0.50 
C)  1.0 
D)  2.0 
E)  63 
A)  0.016 
B)  0.50 
C)  1.0 
D)  2.0 
E)  63

Question 8

For the equilibrium A2(g)   2A(g), if a sample of A2(g) is placed in a sealed container and allowed to come to equilibrium, which graph best represents the relationship between Qc and time as equilibrium is established?

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 9

Which statement is correct?

Accepted Answer

A)  When Q  K then ΔG = 1. 
E)  When Q > K then ΔG = - RT. 
A)  When Q  K then ΔG = 1. 
E)  When Q > K then ΔG = - RT.

Question 10

For the following reaction at equilibrium in a reaction vessel, which one of these changes would cause the I2 concentration to increase? 2NOI(g)   2NO(g) + I2(g), ΔHºrxn = 45.3 kJ/mol

Accepted Answer

A)  Add some NO 
B)  Expand the gas mixture into a larger volume 
C)  Decrease the temperature 
D)  Increase the system pressure 
E)  Remove some NOI 
A)  Add some NO 
B)  Expand the gas mixture into a larger volume 
C)  Decrease the temperature 
D)  Increase the system pressure 
E)  Remove some NOI

Question 11

The formation constant for the reaction Ag+(aq) + 2NH3(aq)   Ag(NH3)2+(aq)
Is Kf = 1.7 × 107 at 25°C. What is ΔG° at this temperature? (R = 8.314 J/K• mol)

Accepted Answer

A)  -1.5 kJ/mol 
B)  -3.5 kJ/mol 
C)  -18 kJ/mol 
D)  -23 kJ/mol 
E)  -41 kJ/mol 
A)  -1.5 kJ/mol 
B)  -3.5 kJ/mol 
C)  -18 kJ/mol 
D)  -23 kJ/mol 
E)  -41 kJ/mol

Question 12

At a certain temperature the reaction CO2(g) + H2(g)   CO(g) + H2O(g)
Has Kc = 2.50. If 2.00 mol of carbon dioxide and 1.50 mol of hydrogen are placed in a 5.00-L vessel and equilibrium is established, what is the equilibrium concentration of carbon monoxide?

Accepted Answer

A)  0.209 M 
B)  1.33 M 
C)  0.267 M 
D)  0.667 M 
E)  0.600 M 
A)  0.209 M 
B)  1.33 M 
C)  0.267 M 
D)  0.667 M 
E)  0.600 M

Question 13

Which substances are included in the equilibrium constant expression, Kc?

Accepted Answer

A)  Only pure solids 
B)  Only pure liquids 
C)  Only pure solids and liquids 
D)  Only gases and dissolved substances 
E)  All participating substances 
A)  Only pure solids 
B)  Only pure liquids 
C)  Only pure solids and liquids 
D)  Only gases and dissolved substances 
E)  All participating substances

Question 14

If Q<K then less reactants are observed as the reaction proceeds to ________.

Accepted Answer

The answer of If Q<K then less reactants are observed...

Question 15

If, in a particular process, reactants are able to form products, and products are also able to form reactants, then this process may be described as

Accepted Answer

A)  a reversible process. 
B)  an elementary process. 
C)  at equilibrium. 
D)  forbidden. 
E)  a forward process. 
A)  a reversible process. 
B)  an elementary process. 
C)  at equilibrium. 
D)  forbidden. 
E)  a forward process.

Question 16

Suppose 50.0 g of N2O4 is introduced into an evacuated 2.00-L vessel and allowed to come to equilibrium with its decomposition product, N2O4(g)   2NO2(g). For this reaction Kc = 0.133. Once the system has reached equilibrium, 5.00 g of NO2 is injected into the vessel, and the system is allowed to equilibrate once again. What is the mass of N2O4 in the final equilibrium mixture?

Accepted Answer

A)  39.5 g 
B)  35.3 g 
C)  30.3 g 
D)  25.2 g 
E)  43.7 g 
A)  39.5 g 
B)  35.3 g 
C)  30.3 g 
D)  25.2 g 
E)  43.7 g

Question 17

When the following reaction is at equilibrium
2NOCl(g)   2NO(g) + Cl2(g)
then [NO]2 [Cl2] = Kc [NOCl]2.

Accepted Answer

A) True 
 B)False

Question 18

Consider this reaction at equilibrium at a total pressure: 2H2O(g) + O2(g)   2H2O2(g)
Suppose the volume of this system is twice its initial volume and then equilibrium is reestablished. The new equilibrium total pressure will be

Accepted Answer

A)  more than half the total initial pressure. 
B)  twice the total pressure. 
C)  less than half the total initial pressure. 
D)  unchanged. 
E)  exactly one half of the initial total pressure. 
A)  more than half the total initial pressure. 
B)  twice the total pressure. 
C)  less than half the total initial pressure. 
D)  unchanged. 
E)  exactly one half of the initial total pressure.

Question 19

At 35ºC, the equilibrium constant for the reaction 2NOCl(g)   2NO(g) + Cl2(g) is Kc = 1.6 × 10-5. An equilibrium mixture was found to have the following concentrations of Cl2 and NOCl: [Cl2] = 1.2 × 10-2 M; [NOCl] = 2.8 × 10-1 M. Calculate the concentration of NO(g) at equilibrium.

Accepted Answer

A)  1.0 × 10-4 M 
B)  1.0 × 10-2 M 
C)  2.8 × 10-1 M 
D)  2.4 × 10-2 M 
E)  1.6 × 10-3 M 
A)  1.0 × 10-4 M 
B)  1.0 × 10-2 M 
C)  2.8 × 10-1 M 
D)  2.4 × 10-2 M 
E)  1.6 × 10-3 M

Question 20

A change in the temperature can change the value of the equilibrium constant.

Accepted Answer

A) True 
 B)False

Exam 15: Chemical Equilibrium

The observation that at equilibrium, the reaction quotient equals the equilibrium constant, is representative of which law?

Hydrogen peroxide (H2O2) decomposes according to the following equation. H2O2(l) → H2O(l) + ½O2(g). What is KP for this reaction at 25°C? (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K • mol, R = 8.314 J/K • mol)

Increasing the temperature of an exothermic reaction causes the equilibrium constant to increase and shifts the equilibrium toward products.

The equilibrium constant expression for the reaction CuO(s) + H2(g) Cu(s) + H2O(g) is Kc = [H2]/[H2O].

Consider the equilibrium equation C(s) + O2(g) CO2(g), where ΔHrxn = -393.5 kJ/mol. The reaction will shift toward the ________ if the temperature of the system is decreased.

Consider the chemical reaction 2NH3(g) N2(g) + 3H2(g). The equilibrium is to be established in a 1.0-L container at 1000 K, where Kc = 4.0 × 10-2. Initially, 1.22 moles of NH3(g) are present. What is the equilibrium concentration of H2(g)?

Consider the reversible reaction: 2NO2(g) N2O4(g) If the concentrations of both NO2 and N2O4 are each 0.016 M, what is the value of Qc?

For the equilibrium A2(g) 2A(g), if a sample of A2(g) is placed in a sealed container and allowed to come to equilibrium, which graph best represents the relationship between Qc and time as equilibrium is established?

Which statement is correct?

For the following reaction at equilibrium in a reaction vessel, which one of these changes would cause the I2 concentration to increase? 2NOI(g) 2NO(g) + I2(g), ΔHºrxn = 45.3 kJ/mol

The formation constant for the reaction Ag+(aq) + 2NH3(aq) Ag(NH3)2+(aq) Is Kf = 1.7 × 107 at 25°C. What is ΔG° at this temperature? (R = 8.314 J/K• mol)

At a certain temperature the reaction CO2(g) + H2(g) CO(g) + H2O(g) Has Kc = 2.50. If 2.00 mol of carbon dioxide and 1.50 mol of hydrogen are placed in a 5.00-L vessel and equilibrium is established, what is the equilibrium concentration of carbon monoxide?

Which substances are included in the equilibrium constant expression, Kc?

If Q<K then less reactants are observed as the reaction proceeds to ________.

If, in a particular process, reactants are able to form products, and products are also able to form reactants, then this process may be described as

When the following reaction is at equilibrium 2NOCl(g) 2NO(g) + Cl2(g) then [NO]2 [Cl2] = Kc [NOCl]2.

Consider this reaction at equilibrium at a total pressure: 2H2O(g) + O2(g) 2H2O2(g) Suppose the volume of this system is twice its initial volume and then equilibrium is reestablished. The new equilibrium total pressure will be

At 35ºC, the equilibrium constant for the reaction 2NOCl(g) 2NO(g) + Cl2(g) is Kc = 1.6 × 10-5. An equilibrium mixture was found to have the following concentrations of Cl2 and NOCl: [Cl2] = 1.2 × 10-2 M; [NOCl] = 2.8 × 10-1 M. Calculate the concentration of NO(g) at equilibrium.

A change in the temperature can change the value of the equilibrium constant.

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Hydrogen peroxide (H₂O₂) decomposes according to the following equation. H₂O₂(l) → H₂O(l) + ½O₂(g). What is K_P for this reaction at 25°C? (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K • mol, R = 8.314 J/K • mol)

The equilibrium constant expression for the reaction CuO(s) + H₂(g) Cu(s) + H₂O(g) is K_c = [H₂]/[H₂O].

Consider the equilibrium equation C(s) + O₂(g) CO₂(g), where ΔH_rxn = -393.5 kJ/mol. The reaction will shift toward the ________ if the temperature of the system is decreased.

Consider the chemical reaction 2NH₃(g) N₂(g) + 3H₂(g). The equilibrium is to be established in a 1.0-L container at 1000 K, where K_c = 4.0 × 10^-2. Initially, 1.22 moles of NH₃(g) are present. What is the equilibrium concentration of H₂(g)?

Consider the reversible reaction: 2NO₂(g) N₂O₄(g) If the concentrations of both NO₂ and N₂O₄ are each 0.016 M, what is the value of Q_c?

For the equilibrium A₂(g) 2A(g), if a sample of A₂(g) is placed in a sealed container and allowed to come to equilibrium, which graph best represents the relationship between Q_c and time as equilibrium is established?

For the following reaction at equilibrium in a reaction vessel, which one of these changes would cause the I₂ concentration to increase? 2NOI(g) 2NO(g) + I₂(g), ΔHº_rxn= 45.3 kJ/mol

The formation constant for the reaction Ag⁺(aq) + 2NH₃(aq) Ag(NH₃)₂⁺(aq) Is K_f = 1.7 × 10⁷ at 25°C. What is ΔG° at this temperature? (R = 8.314 J/K• mol)

At a certain temperature the reaction CO₂(g) + H₂(g) CO(g) + H₂O(g) Has K_c = 2.50. If 2.00 mol of carbon dioxide and 1.50 mol of hydrogen are placed in a 5.00-L vessel and equilibrium is established, what is the equilibrium concentration of carbon monoxide?

Which substances are included in the equilibrium constant expression, K_c?

When the following reaction is at equilibrium 2NOCl(g) 2NO(g) + Cl₂(g) then [NO]² [Cl₂] = K_c[NOCl]².

Consider this reaction at equilibrium at a total pressure: 2H₂O(g) + O₂(g) 2H₂O₂(g) Suppose the volume of this system is twice its initial volume and then equilibrium is reestablished. The new equilibrium total pressure will be

At 35ºC, the equilibrium constant for the reaction 2NOCl(g) 2NO(g) + Cl₂(g) is K_c = 1.6 × 10^-5. An equilibrium mixture was found to have the following concentrations of Cl₂ and NOCl: [Cl₂] = 1.2 × 10^-2^M; [NOCl] = 2.8 × 10^-1^M. Calculate the concentration of NO(g) at equilibrium.