Question 1

Once a reaction system reaches equilibrium,the concentrations of reactions and products no longer change.

Accepted Answer

A) True 
 B)False  True

Question 2

Consider the following gas-phase equilibrium reaction:
   
If 1.0 mol of NO is introduced into a 1.0 L container at 2000°C,what is the concentration of NO when equilibrium is reached?

Accepted Answer

[NO] = 1.0 $\times$ 10^-2 mol L^-1

Question 3

The reaction quotient for a gas phase reaction has a value of 2000.If the number of moles of reactants in the reaction equation is equal to that of the products,which of the following statements is true?

Accepted Answer

A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) When the system is at equilibrium,the concentrations of the products will be much larger than the concentrations of the reactants. 
D) The concentrations of the products are generally larger than the concentrations of the reactants. 
E) None of these statements is true. 
A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) When the system is at equilibrium,the concentrations of the products will be much larger than the concentrations of the reactants. 
D) The concentrations of the products are generally larger than the concentrations of the reactants. 
E) None of these statements is true. D

Question 4

A mixture 0.500 mole of carbon monoxide and 0.400 mole of bromine was placed into a rigid 1.00-L container and the system was allowed to come to equilibrium.The equilibrium concentration of COBr2 was 0.233 M.What is the value of Kc for this reaction?
CO(g)+ Br2(g)  
COBr2(g)

Accepted Answer

A) 5.23 
B) 1.22 
C) 1.165 
D) 0.858 
E) 0.191 
A) 5.23 
B) 1.22 
C) 1.165 
D) 0.858 
E) 0.191

Question 5

Consider the equilibrium:
   
Predict and explain how or whether the following actions would affect this equilibrium.
a.adding more solid A
b.lowering the temperature
c.increasing the pressure on the system by reducing its volume
d.adding helium gas to increase the total pressure

Accepted Answer

a.No effect.Pure solids and liquids have

Question 6

What is the mass-action expression,Qc,for the following chemical reaction?
Cu2+(aq)+ 4NH3(aq)  
Cu(NH3)42+(aq)

Accepted Answer

A) 
  
B) 
  
C) 
  
D) 
  
E) None of these is the correct mass-action expression. 
A) 
  
B) 
  
C) 
  
D) 
  
E) None of these is the correct mass-action expression.

Question 7

The equilibrium constant,Kc ,for the decomposition of COBr2
 COBr2(g)  
CO(g)+ Br2(g)
Is 0.190.What is Kc for the following reaction?
2CO(g)+ 2Br2(g)  
2COBr2(g)

Accepted Answer

A) 0.0361 
B) 2.63 
C) 5.62 
D) 10.5 
E) 27.7 
A) 0.0361 
B) 2.63 
C) 5.62 
D) 10.5 
E) 27.7

Question 8

Magnesium hydroxide is used in several antacid formulations.When it is added to water it dissociates into magnesium and hydroxide ions.
Mg(OH)2(s)  
Mg2+(aq)+ 2OH-(aq)
The equilibrium constant at 25°C is 8.9 $\times$ 10-12.One hundred grams of magnesium hydroxide is added to 1.00 L of water and equilibrium is established.What happens to the solution if another 10 grams of Mg(OH)2 are now added to the mixture?

Accepted Answer

A) The hydroxide ion concentration will decrease. 
B) The hydroxide ion concentration will increase. 
C) The hydroxide ion concentration will be unchanged. 
D) The solution will become supersaturated. 
E) None of these conclusions is justified without additional information. 
A) The hydroxide ion concentration will decrease. 
B) The hydroxide ion concentration will increase. 
C) The hydroxide ion concentration will be unchanged. 
D) The solution will become supersaturated. 
E) None of these conclusions is justified without additional information.

Question 9

For a gas-phase equilibrium,a change in the pressure of any single reactant or product will affect the amounts of other substances involved in the equilibrium.

Accepted Answer

A) True 
 B)False

Question 10

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 1.5 mol of hydrogen are placed in a 5.00 L vessel and equilibrium is established,what will be the concentration of carbon monoxide?

Accepted Answer

A) 0.091 M 
B) 0.191 M 
C) 0.209 M 
D) 0.913 M 
E) 1.05 M 
A) 0.091 M 
B) 0.191 M 
C) 0.209 M 
D) 0.913 M 
E) 1.05 M

Question 11

The reaction quotient,Qc,for a reaction has a value of 75 while the equilibrium constant,Kc,has a value of 195.Which of the following statements is accurate?

Accepted Answer

A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) The concentrations of the products will be much smaller than the concentrations of the reactants when the system is at equilibrium. 
D) The concentrations of the products will be about the same as the concentrations of the reactants when the system is at equilibrium. 
E) None of these statements is accurate. 
A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) The concentrations of the products will be much smaller than the concentrations of the reactants when the system is at equilibrium. 
D) The concentrations of the products will be about the same as the concentrations of the reactants when the system is at equilibrium. 
E) None of these statements is accurate.

Question 12

For a gas-phase equilibrium,a change in the pressure of any single reactant or product will change Kp.

Accepted Answer

A) True 
 B)False

Question 13

Write the mass-action expression,Qc,for the following chemical reaction.
NO(g)+  
Br2(g)  
NOBr(g)

Accepted Answer

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

Question 14

When a chemical system is at equilibrium,

Accepted Answer

A) the concentrations of the reactants are equal to the concentrations of the products. 
B) the concentrations of the reactants and products have reached constant values. 
C) the forward and reverse reactions have stopped. 
D) the reaction quotient,Q,has reached a maximum. 
E) the reaction quotient,Q,has reached a minimum. 
A) the concentrations of the reactants are equal to the concentrations of the products. 
B) the concentrations of the reactants and products have reached constant values. 
C) the forward and reverse reactions have stopped. 
D) the reaction quotient,Q,has reached a maximum. 
E) the reaction quotient,Q,has reached a minimum.

Question 15

The reaction system
CS2(g)+ 4H2(g)  
CH4(g)+ 2H2S(g)
Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of hydrogen is doubled?

Accepted Answer

A) As equilibrium is reestablished,the partial pressure of carbon disulfide increases. 
B) As equilibrium is reestablished,the partial pressure of methane,CH4,decreases. 
C) As equilibrium is reestablished,the partial pressure of hydrogen decreases. 
D) As equilibrium is reestablished,the partial pressure of hydrogen sulfide decreases. 
E) As equilibrium is reestablished,all the partial pressures will decrease. 
A) As equilibrium is reestablished,the partial pressure of carbon disulfide increases. 
B) As equilibrium is reestablished,the partial pressure of methane,CH4,decreases. 
C) As equilibrium is reestablished,the partial pressure of hydrogen decreases. 
D) As equilibrium is reestablished,the partial pressure of hydrogen sulfide decreases. 
E) As equilibrium is reestablished,all the partial pressures will decrease.

Question 16

The following reaction is at equilibrium in a closed container.
CuSO4.5H2O(s)  
CuSO4(s)+ 5H2O(g)
Which,if any,of the following actions will lead to an increase in the pressure of H2O present at equilibrium?

Accepted Answer

A) increasing the volume of the container 
B) decreasing the volume of the container 
C) adding a catalyst 
D) removing some solid CuSO4 
E) None of these choices is correct. 
A) increasing the volume of the container 
B) decreasing the volume of the container 
C) adding a catalyst 
D) removing some solid CuSO4 
E) None of these choices is correct.

Question 17

The reaction system
POCl3(g)  
POCl(g)+ Cl2(g)
Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of chlorine is reduced by 50%?

Accepted Answer

A) POCl3 will be consumed as equilibrium is established. 
B) POCl will be consumed as equilibrium is established. 
C) Chlorine will be consumed as equilibrium is established. 
D) The partial pressure of POCl will decrease while the partial pressure of Cl2 increases as equilibrium is established. 
E) The volume will have to decrease before equilibrium can be reestablished. 
A) POCl3 will be consumed as equilibrium is established. 
B) POCl will be consumed as equilibrium is established. 
C) Chlorine will be consumed as equilibrium is established. 
D) The partial pressure of POCl will decrease while the partial pressure of Cl2 increases as equilibrium is established. 
E) The volume will have to decrease before equilibrium can be reestablished.

Question 18

The equilibrium constant for the reaction of bromine with chlorine to form bromine monochloride is 58.0 at a certain temperature.
Br2(g)+ Cl2(g)  
2BrCl(g)
What is the equilibrium constant for the following reaction?
BrCl(g)  
 
Br2(g)+  
Cl2(g)

Accepted Answer

A) 2.97 $\times$ 10-4 
B) 1.72 $\times$ 10-2 
C) 3.45 $\times$ 10-2 
D) 1.31 $\times$ 10-1 
E) > 1.00 
A) 2.97 $\times$ 10-4 
B) 1.72 $\times$ 10-2 
C) 3.45 $\times$ 10-2 
D) 1.31 $\times$ 10-1 
E) > 1.00

Question 19

Consider the equilibrium reaction: H2(g)+ Br2(g)  
2HBr(g)
Which of the following correctly describes the relationship between Kc and Kp for the reaction?

Accepted Answer

A) Kp = Kc 
B) Kp = (RT)Kc 
C) Kp = (RT)2Kc 
D) Kp = Kc/RT 
E) Kp = Kc/(RT)2 
A) Kp = Kc 
B) Kp = (RT)Kc 
C) Kp = (RT)2Kc 
D) Kp = Kc/RT 
E) Kp = Kc/(RT)2

Question 20

If Q > K,more products need to be formed as the reaction proceeds to equilibrium.

Accepted Answer

A) True 
 B)False

Exam 17: Equilibrium: the Extent of Chemical Reactions

Once a reaction system reaches equilibrium,the concentrations of reactions and products no longer change.

Consider the following gas-phase equilibrium reaction: If 1.0 mol of NO is introduced into a 1.0 L container at 2000°C,what is the concentration of NO when equilibrium is reached?

The reaction quotient for a gas phase reaction has a value of 2000.If the number of moles of reactants in the reaction equation is equal to that of the products,which of the following statements is true?

A mixture 0.500 mole of carbon monoxide and 0.400 mole of bromine was placed into a rigid 1.00-L container and the system was allowed to come to equilibrium.The equilibrium concentration of COBr2 was 0.233 M.What is the value of Kc for this reaction? CO(g)+ Br2(g) COBr2(g)

Consider the equilibrium: Predict and explain how or whether the following actions would affect this equilibrium. a.adding more solid A b.lowering the temperature c.increasing the pressure on the system by reducing its volume d.adding helium gas to increase the total pressure

What is the mass-action expression,Qc,for the following chemical reaction? Cu2+(aq)+ 4NH3(aq) Cu(NH3)42+(aq)

The equilibrium constant,Kc ,for the decomposition of COBr2 COBr2(g) CO(g)+ Br2(g) Is 0.190.What is Kc for the following reaction? 2CO(g)+ 2Br2(g) 2COBr2(g)

For a gas-phase equilibrium,a change in the pressure of any single reactant or product will affect the amounts of other substances involved in the equilibrium.

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 1.5 mol of hydrogen are placed in a 5.00 L vessel and equilibrium is established,what will be the concentration of carbon monoxide?

The reaction quotient,Qc,for a reaction has a value of 75 while the equilibrium constant,Kc,has a value of 195.Which of the following statements is accurate?

For a gas-phase equilibrium,a change in the pressure of any single reactant or product will change Kp.

Write the mass-action expression,Qc,for the following chemical reaction. NO(g)+ Br2(g) NOBr(g)

When a chemical system is at equilibrium,

The reaction system CS2(g)+ 4H2(g) CH4(g)+ 2H2S(g) Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of hydrogen is doubled?

The following reaction is at equilibrium in a closed container. CuSO4.5H2O(s) CuSO4(s)+ 5H2O(g) Which,if any,of the following actions will lead to an increase in the pressure of H2O present at equilibrium?

The reaction system POCl3(g) POCl(g)+ Cl2(g) Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of chlorine is reduced by 50%?

The equilibrium constant for the reaction of bromine with chlorine to form bromine monochloride is 58.0 at a certain temperature. Br2(g)+ Cl2(g) 2BrCl(g) What is the equilibrium constant for the following reaction? BrCl(g) Br2(g)+ Cl2(g)

Consider the equilibrium reaction: H2(g)+ Br2(g) 2HBr(g) Which of the following correctly describes the relationship between Kc and Kp for the reaction?

If Q > K,more products need to be formed as the reaction proceeds to equilibrium.

Keys to the Study of Chemistry

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids,solids,and Phase Changes

The Properties of Solutions

The Main-Group Elements: Applying Principles of Bonding and Structure

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics: Entropy, free Energy, and the Direction of Chemical Reactions

Electrochemistry: Chemical Change and Electrical Work

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

A mixture 0.500 mole of carbon monoxide and 0.400 mole of bromine was placed into a rigid 1.00-L container and the system was allowed to come to equilibrium.The equilibrium concentration of COBr₂ was 0.233 M.What is the value of K_c for this reaction? CO(g)+ Br₂(g) COBr₂(g)

What is the mass-action expression,Q_c,for the following chemical reaction? Cu²⁺(aq)+ 4NH₃(aq) Cu(NH₃)₄²⁺(aq)

The equilibrium constant,K_c ,for the decomposition of COBr₂ COBr₂(g) CO(g)+ Br₂(g) Is 0.190.What is K_c for the following reaction? 2CO(g)+ 2Br₂(g) 2COBr₂(g)

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 1.5 mol of hydrogen are placed in a 5.00 L vessel and equilibrium is established,what will be the concentration of carbon monoxide?

The reaction quotient,Q_c,for a reaction has a value of 75 while the equilibrium constant,K_c,has a value of 195.Which of the following statements is accurate?

For a gas-phase equilibrium,a change in the pressure of any single reactant or product will change K_p.

Write the mass-action expression,Q_c,for the following chemical reaction. NO(g)+ Br₂(g) NOBr(g)

The reaction system CS₂(g)+ 4H₂(g) CH₄(g)+ 2H₂S(g) Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of hydrogen is doubled?

The following reaction is at equilibrium in a closed container. CuSO₄.5H₂O(s) CuSO₄(s)+ 5H₂O(g) Which,if any,of the following actions will lead to an increase in the pressure of H₂O present at equilibrium?

The reaction system POCl₃(g) POCl(g)+ Cl₂(g) Is at equilibrium.Which of the following statements describes the behavior of the system if the partial pressure of chlorine is reduced by 50%?

The equilibrium constant for the reaction of bromine with chlorine to form bromine monochloride is 58.0 at a certain temperature. Br₂(g)+ Cl₂(g) 2BrCl(g) What is the equilibrium constant for the following reaction? BrCl(g) Br₂(g)+ Cl₂(g)

Consider the equilibrium reaction: H₂(g)+ Br₂(g) 2HBr(g) Which of the following correctly describes the relationship between K_c and K_p for the reaction?