Question 1

Write the mass-action expression, Qc , for the following chemical reaction.

Accepted Answer

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

Question 2

Sodium hydrogen carbonate decomposes above 110 $\degree$C to form sodium carbonate, water, and carbon dioxide.   One thousand grams of sodium hydrogen carbonate are added to a reaction vessel, the temperature is increased to 200 $\degree$C, and the system comes to equilibrium. What happens in this system if another 50 g of sodium carbonate are now added?

Accepted Answer

A)  The partial pressure of carbon dioxide will increase. 
B)  The partial pressure of carbon dioxide will decrease. 
C)  The partial pressure of carbon dioxide will be unchanged. 
D)  The amounts of all products will be greater when equilibrium is reestablished. 
E)  None of these conclusions is justified without knowing the equilibrium constant. 
A)  The partial pressure of carbon dioxide will increase. 
B)  The partial pressure of carbon dioxide will decrease. 
C)  The partial pressure of carbon dioxide will be unchanged. 
D)  The amounts of all products will be greater when equilibrium is reestablished. 
E)  None of these conclusions is justified without knowing the equilibrium constant.

Question 3

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 4

The equilibrium constant, Kp, for the reaction   at 986 $\degree$C is 0.63. A rigid cylinder at that temperature contains 1.2 atm of carbon monoxide, 0.20 atm of water vapor, 0.30 atm of carbon dioxide, and 0.27 atm of hydrogen. Is the system at equilibrium?

Accepted Answer

A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  Need to know the volume of the container before deciding. 
E)  Need to know the starting concentrations of all substances before deciding. 
A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  Need to know the volume of the container before deciding. 
E)  Need to know the starting concentrations of all substances before deciding.

Question 5

Magnesium hydroxide is used in several antacid formulations. When it is added to water it dissociates into magnesium and hydroxide ions.   The equilibrium constant at 25 $\degree$C is 8.9 *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 6

At 25 $\degree$C, the equilibrium constant Kc for the reaction 2A(g)   B(g) + C(g) is 0.035. A mixture of 8.00 moles of B and 12.00 moles of C in a 20.0 L container is allowed to come to equilibrium. What is the equilibrium concentration of A?

Accepted Answer

A)  < 0.100 M 
B)  0.339 M 
C)  0.678 M 
D)  6.78 M 
E)  13.56 M 
A)  < 0.100 M 
B)  0.339 M 
C)  0.678 M 
D)  6.78 M 
E)  13.56 M

Question 7

In a chemical reaction, if the starting concentrations of reactants are increased, then the equilibrium constant Kc will also increase.

Accepted Answer

A) True 
 B)False

Question 8

Consider the equilibrium reaction:   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 9

The following reaction is at equilibrium in a sealed container.   Which, if any, of the following actions will increase the value of the equilibrium constant, Kc?

Accepted Answer

A)  adding a catalyst 
B)  adding more N2 
C)  increasing the pressure 
D)  lowering the temperature 
E)  None of these choices is correct. 
A)  adding a catalyst 
B)  adding more N2 
C)  increasing the pressure 
D)  lowering the temperature 
E)  None of these choices is correct.

Question 10

Write the mass-action expression, Qc, for the following chemical reaction.

Accepted Answer

A)    
B)    
C)    
D)    
E)  None of these choices is correct. 
A)    
B)    
C)    
D)    
E)  None of these choices is correct.

Question 11

The following reaction is at equilibrium at one atmosphere, in a closed container.   Which, if any, of the following actions will decrease the total amount of CO2 gas present at equilibrium?

Accepted Answer

A)  adding N2 gas to double the pressure 
B)  adding more solid NaOH 
C)  decreasing the volume of the container 
D)  removing half of the solid NaHCO3 
E)  None of these choices is correct. 
A)  adding N2 gas to double the pressure 
B)  adding more solid NaOH 
C)  decreasing the volume of the container 
D)  removing half of the solid NaHCO3 
E)  None of these choices is correct.

Question 12

Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide.   
At 400 $\degree$C, Kp = 0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400 $\degree$C.

Accepted Answer

A)  0.103 atm 
B)  0.215 atm 
C)  0.232 atm 
D)  0.464 atm 
E)  2.00 atm 
A)  0.103 atm 
B)  0.215 atm 
C)  0.232 atm 
D)  0.464 atm 
E)  2.00 atm

Question 13

The reaction of nitric oxide to form dinitrogen oxide and nitrogen dioxide is exothermic.   What effect will be seen if the temperature of the system at equilibrium is raised by 25 $\degree$C?

Accepted Answer

A)  The partial pressure of NO will increase. 
B)  The partial pressure of NO will decrease. 
C)  The partial pressure of NO2 will increase. 
D)  The partial pressures of NO and N2O will increase. 
E)  All three partial pressures will increase. 
A)  The partial pressure of NO will increase. 
B)  The partial pressure of NO will decrease. 
C)  The partial pressure of NO2 will increase. 
D)  The partial pressures of NO and N2O will increase. 
E)  All three partial pressures will increase.

Question 14

A mixture of 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?

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 15

The equilibrium constant, Kp, for the reaction   is 55.2 at 425 $\degree$C. A rigid cylinder at that temperature contains 0.127 atm of hydrogen, 0.134 atm of iodine, and 1.055 atm of hydrogen iodide. Is the system at equilibrium?

Accepted Answer

A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  Need to know the volume of the container before deciding. 
E)  Need to know the starting concentrations of all substances before deciding. 
A)  Yes. 
B)  No, the forward reaction must proceed to establish equilibrium. 
C)  No, the reverse reaction must proceed to establish equilibrium. 
D)  Need to know the volume of the container before deciding. 
E)  Need to know the starting concentrations of all substances before deciding.

Question 16

Consider the reversible reaction:   If the concentrations of both NO2 and N2O4 are 0.016 mol L¯1, 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 17

Carbon monoxide and chlorine combine in an equilibrium reaction to produce the highly toxic product, phosgene (COCl2).   If the equilibrium constant for this reaction is Kc = 248, predict, if possible, what will happen when the reactants and product are combined with the concentrations shown. [CO] = [Cl2] = 0.010 M; [COCl2] = 0.070 M

Accepted Answer

A)  The reaction will proceed to the right. 
B)  The reaction will proceed to the left. 
C)  The reaction is at equilibrium, and no change in concentrations will occur. 
D)  The container volume needs to be specified before a prediction can be made. 
E)  The temperature needs to be specified before a prediction can be made. 
A)  The reaction will proceed to the right. 
B)  The reaction will proceed to the left. 
C)  The reaction is at equilibrium, and no change in concentrations will occur. 
D)  The container volume needs to be specified before a prediction can be made. 
E)  The temperature needs to be specified before a prediction can be made.

Question 18

Nitrogen dioxide decomposes according to the reaction   at 25 $\degree$C. What is the value for Kc?

Accepted Answer

A)  1.81 * 10¯16 
B)  1.83 * 10¯14 
C)  4.48 *10¯13 
D)  1.10 *10¯11 
E)  1.11 * 10¯9 
A)  1.81 * 10¯16 
B)  1.83 * 10¯14 
C)  4.48 *10¯13 
D)  1.10 *10¯11 
E)  1.11 * 10¯9

Question 19

At high temperatures, carbon reacts with O2 to produce CO as follows:   When 0.350 mol of O2 and excess carbon were placed in a 5.00-L container and heated, the equilibrium concentration of CO was found to be 0.060 M. What is the equilibrium constant, Kc, for this reaction?

Accepted Answer

A)  0.010 
B)  0.072 
C)  0.090 
D)  0.17 
E)  1.2 
A)  0.010 
B)  0.072 
C)  0.090 
D)  0.17 
E)  1.2

Question 20

What is the mass-action expression, Qc, for the following chemical reaction?

Accepted Answer

A)    
B)    
C)    
D)    
E)  None of these choices is correct. 
A)    
B)    
C)    
D)    
E)  None of these choices is correct.

Write the mass-action expression, Q_c , for the following chemical reaction.

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?

In a chemical reaction, if the starting concentrations of reactants are increased, then the equilibrium constant K_c will also increase.

Consider the equilibrium reaction: Which of the following correctly describes the relationship between K_c and K_p for the reaction?

The following reaction is at equilibrium in a sealed container. Which, if any, of the following actions will increase the value of the equilibrium constant, K_c?

Write the mass-action expression, Q_c, for the following chemical reaction.

The following reaction is at equilibrium at one atmosphere, in a closed container. Which, if any, of the following actions will decrease the total amount of CO₂ gas present at equilibrium?

A mixture of 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?

Consider the reversible reaction: If the concentrations of both NO₂ and N₂O₄ are 0.016 mol L¯¹, what is the value of Q_c?

Nitrogen dioxide decomposes according to the reaction $Nitrogen dioxide decomposes according to the reaction at 25 \degree C. What is the value for K<sub>c</sub>?$ at 25 $\degree$ C. What is the value for K_c?

At high temperatures, carbon reacts with O₂ to produce CO as follows: When 0.350 mol of O₂ and excess carbon were placed in a 5.00-L container and heated, the equilibrium concentration of CO was found to be 0.060 M. What is the equilibrium constant, K_c, for this reaction?

What is the mass-action expression, Q_c, for the following chemical reaction?

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 Mixtures: Solutions and Colloids

Periodic Patterns in the Main-Group Elements

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 Elements in Nature and Industry

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

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Exam 17: Equilibrium: the Extent of Chemical Reactions