Whitten Ch.17

Which of the following is the best definition of chemical equilibrium? a. A condition where the forward and reverse reaction rates of a reversible reaction are equal and constant. b. There are equal amounts of reactants and products. c. The forward and reverse reaction rates have stopped. d. The product concentrations are larger than reactant concentrations. e. The reactant concentrations are larger than product concentrations.

a. A condition where the forward and reverse reaction rates of a reversible reaction are equal and constant.

Which of the numbered responses lists all the following stresses that would shift the equilibrium to the right (favor the forward reaction), and no other stresses? 2NOCl(g) + 75 kJ 2NO(g) + Cl2(g) I. Add more NOCl. II. Remove some Cl2. III. Lower the temperature. IV. Add more NO. a. I and II b. I, II, and III c. I and III d. II and IV e. II, III, and IV

a. I and II

Consider the following reaction: AB(s) + C2(g) AC(g) + BC(g) + heat Which of the following statements is false? a. Increasing PC2 will cause a shift to the left. b. Adding a catalyst will not affect the equilibrium. c. Decreasing the temperature will cause a shift to the right. d. Adding more AB(s) will not affect the equilibrium. e. Increasing PAC or PBC will cause a shift to the left.

a. Increasing PC2 will cause a shift to the left.

Consider the following system at equilibrium: 2SO3(g) 2SO2(g) + O2(g) Kc = 2.90 x 10-2 and ΔHo = 198 kJ/mol at 1150K. Which of the following changes will favor the production of SO2? a. Increasing the temperature b. Increasing the pressure c. Adding O2 gas d. Adding sulfur, S e. Adding a catalyst

a. Increasing the temperature

When the pressure of an equilibrium mixture of SO2, O2, and SO3 is doubled at constant temperature, what the effect on Kp? 2SO2(g) + O2(g) 2SO3(g) a. Kp is halved. b. Kp is doubled. c. Kp is unchanged. d. Kp is tripled. e. Kp is decreased by a third.

a. Kp is halved.

At a certain temperature Kc = 25 and a reaction vessel contains a mixture with the following concentrations: [H2] = 0.10 M, [Br2] = 0.10 M and [HBr] = 0.50 M. Which of the following statements concerning the reaction and the reaction quotient, Q, is true? H2(g) + Br2(g) 2HBr(g) a. Q = Kc b. Q < Kc; more HBr will be produced. c. Q < Kc; more H2 and Br2 will be produced. d. Q > Kc; more HBr will be produced. e. Q > Kc; more H2 and Br2 will be produced.

a. Q = Kc

The equilibrium constant, K, for the following reaction is 1.96 x 105 at 548K NH3(g) + HCl(g) NH4Cl (s) Which of the following statements is true about the above reaction? a. The reaction favors the products and the concentrations of NH3 and HCl will be low at equilibrium. b. The reaction favors the reactants and the concentrations of NH3 and HCl will be high at equilibrium c. The reaction favors the product and the equilibrium concentration of NH4Cl equals 1. d. The reaction favors the reactants and the equilibrium concentration of NH4Cl equals 1. e. Two of the above are true.

a. The reaction favors the products and the concentrations of NH3 and HCl will be low at equilibrium.

Which of the following is always true for a reaction where Kc is at 25°C? a. The reaction mixture contains mostly products at equilibrium. b. The reaction mixture contains mostly reactants at equilibrium. c. The rate of reaction is very fast. d. There are approximately equal moles of reactants and products at equilibrium. e. Both A and C.

a. The reaction mixture contains mostly products at equilibrium.

Addition of CO to an equilibrium mixture of the above reaction will a. cause [CO2] to increase c. have no effect b. cause [H2O] to increase d. cannot be determined

a. cause [CO2] to increase

Suppose the following reaction is at equilibrium at a given temperature and pressure. The pressure is then increased at constant temperature, by compressing the reaction mixture, and the mixture is allowed to re-establish equilibrium. At the new equilibrium ____. N2(g) + 3H2(g) 2NH3(g) a. there is more ammonia than there was originally b. there is less ammonia than there was originally c. there is the same amount of ammonia present as there was originally d. the nitrogen is used up completely e. the amount of ammonia may be either larger or smaller than it was originally, depending on the value of K

a. there is more ammonia than there was originally

The van't Hoff equation relates two equilibrium constants at two different temperatures. Consider a reaction where K298 = 16.3 and ΔH0 = −116 kJ/mol. Which of the following statements is true? a. The reverse reaction is favored at 298 K. b. A decrease in temperature will cause the forward reaction to be favored more. c. An increase in temperature will cause the forward reaction to be favored more. d. The value of K would be larger at 398 K. e. The reaction is endothermic.

b. A decrease in temperature will cause the forward reaction to be favored more.

Which of the following statements about the Haber process is false? a. Fritz Haber, a German scientist, developed the process. b. Higher temperature favors the forward reaction. c. Most NH3 produced by the Haber process is used to make fertilizer. d. Ammonia is synthesized from elemental nitrogen and hydrogen. e. Higher gas pressures favor the forward reaction.

b. Higher temperature favors the forward reaction.

Suppose we let the reaction below come to equilibrium. Then we decrease the total pressure, by increasing the volume of the container. What will be the effect on the net amount of SO3(g) present? 2SO2(g) + O2(g) 2SO3(g) a. It increases. b. It decreases. c. It does not change. d. The question cannot be answered without knowing the value of K. e. The question cannot be answered without knowing the value of ΔH0.

b. It decreases.

Suppose we let this reaction come to equilibrium. Then we increase the temperature of the reaction mixture. What will be the effect on the net amount of SO3(g) present? 2SO2(g) + O2(g) 2SO3(g) + heat a. It increases. b. It decreases. c. It does not change. d. The question cannot be answered without knowing the value of K. e. The question cannot be answered without knowing the value of ΔH0.

b. It decreases.

Which of the following is true about a chemical equilibrium? a. It is microscopically static and macroscopically dynamic. b. It is microscopically dynamic and macroscopically static. c. It is microscopically and macroscopically static. d. It is microscopically and macroscopically dynamic.

b. It is microscopically dynamic and macroscopically static.

At a certain temperature Kc = 55 and a reaction vessel contains a mixture with the following concentrations: [SO3] = 0.85 M, [NO] = 1.2 M , [SO2] = 1.5 M and [NO2] = 2.0 M. Which of the following statements concerning the reaction and the reaction quotient, Q, is false? SO3(g) + NO(g) SO2(g) + NO2(g) a. Q < Kc b. Q > Kc c. The reaction is not in equilibrium. d. Product concentrations will increase as equilibrium is approached. e. Reactant concentrations will decrease as equilibrium is approached.

b. Q > Kc

For the reaction, N2O4(g) 2NO2(g), which of the following statements is true about this reaction at equilibrium? a. The concentration of NO2 is equal to the concentration of N2O4 b. The rate of the dissociation of N2O4 is equal to the rate of formation of N2O4 c. The rate constant for the forward reaction is equal to the rate constant for the reverse reaction d. The concentration of NO2 divided by the concentration of N2O4 is equal to a constant e. Two of the above

b. The rate of the dissociation of N2O4 is equal to the rate of formation of N2O4

If you mixed 5.0 mol CO2, 0.10 mol H2, 3.5 mol of CO, and 0.0010 mol H2O in a one-liter container, in which direction would the reaction proceed? a. To the left. b. To the right. c. The above mixture is the equilibrium mixture. d. Cannot tell from the information given.

b. To the right.

For the gas phase reaction below, ΔH0 = −1.6 × 102 kJ for the forward reaction. SO2 + O2 SO3 In order to increase the yield of SO3, the reaction should be run a. at high P, high T. b. at high P, low T. c. at low P, high T. d. at low P, low T. e. at high P, but is independent of T.

b. at high P, low T.

Raising the temperature of the reaction mixture will: a. cause [CO2] to increase c. have no effect b. cause [H2O] to increase d. cannot be determined

b. cause [H2O] to increase

Dinitrogen tetraoxide exists in equilibrium with nitrogen dioxide: N2O4(g) 2NO2(g). At a certain temperature, K = 6.98 x 104. Which of the following statements is true about this reaction? a. the concentration of NO2 is equal to the concentration of N2O4 at equilibrium b. the rate of dissociation of N2O4 is equal to the rate of formation of NO2 at equilibrium c. the reaction will reach equilibrium rapidly d. the rate constant for the forward reaction is equal to the rate constant for the reverse reaction at equilibrium e. two of the above

b. the rate of dissociation of N2O4 is equal to the rate of formation of NO2 at equilibrium

An indicator, HIn, shows a color change from blue to yellow, depending on the acidity of the solution: HIn (aq) H+ (aq) + In- (aq) (blue) (yellow) What color will the indicator change when NaOH is added? a. blue b. yellow c. no color change

b. yellow

Consider the following heterogeneous reaction: Mg(s) + 2H3O+(aq) Mg2+(aq) + H2(g) + 2H2O Which of the following statements is false? a. The amount of magnesium present does not affect the equilibrium position. b. Adding 1.0 atm of N2 to the system would cause the reverse reaction to be favored. c. Increasing causes the forward reaction to be favored. d. Increasing [H3O+] causes the forward reaction to be favored. e. Decreasing [Mg2+] causes the forward reaction to be favored.

c. Increasing causes the forward reaction to be favored.

Suppose we let the reaction below come to equilibrium. Then we decrease the total pressure, by increasing the volume of the container. What will be the effect on the numerical value of the equilibrium constant, K? 2SO2(g) + O2(g) 2SO3(g) + heat a. It increases. b. It decreases. c. It does not change. d. The question cannot be answered without knowing the initial value of K. e. The question cannot be answered without knowing the value of ΔH0.

c. It does not change.

The equilibrium constant, Kc, for the following reaction is 0.0154 at a high temperature. A mixture in a container at this temperature has the concentrations: [H2] = 1.11 M, [I2] = 1.30 M and [HI] = 0.181 M. Which of the following statements concerning the reaction and the reaction quotient, Q, is true? H2(g) + I2(g) 2HI(g) a. Q = Kc b. Q > Kc; more HI will be produced. c. Q > Kc; more H2 and I2 will be produced. d. Q < Kc; more HI will be produced. e. Q < Kc; more H2 and I2 will be produced.

c. Q > Kc; more H2 and I2 will be produced.

Which one of the following would force the forward reaction to completion? CaCO3(s) + 2H3O+(aq) Ca2+(aq) + 3H2O + CO2(g) a. Removing some H3O+ from the reaction mixture, by neutralizing it with base. b. Adding more Ca2+ to the mixture. c. Removing CO2 as it is formed. d. Adding CO2 to the reaction mixture. e. None of these would have any effect on the amount of CaCO3 consumed.

c. Removing CO2 as it is formed.

Consider the following reaction where Kc = 1.18 at 150K: 2HI(g) H2(g) + I2(s) A reaction mixture was found to contain 0.0381 moles of HI, 0.0471 moles of H2, and 0.0364 moles of I2 in a 1.00 L container. Is the reaction at equilibrium? And if not, what direction must it run in order to reach equilibrium? a. The reaction is at equilibrium b. The reaction must run towards the products to reach equilibrium c. The reaction must run towards the reactants to reach equilibrium

c. The reaction must run towards the reactants to reach equilibrium

For the following system at equilibrium, H2(g) + CO2(g) H2O(g) + CO(g) the addition of H2(g) would cause (according to LeChatelier's principle) a. only more H2O(g) to form. b. only more CO(g) to form. c. more H2O(g) and CO(g) to form. d. only more CO2(g) to form. e. no change in amounts of products or reactants.

c. more H2O(g) and CO(g) to form.

Suppose the following reaction is at equilibrium at a given temperature and pressure. The pressure is then increased at constant temperature, by compressing the reaction mixture, and the mixture is allowed to re-establish equilibrium. At the new equilibrium ____. H2(g) + Cl2(g) 2HCl(g) a. there is more hydrogen chloride than there was originally b. there is less hydrogen chloride than there was originally c. there is the same amount of hydrogen chloride as there was originally d. the hydrogen and chloride are completely used up e. the amount of hydrogen chloride may be either larger or smaller than it was originally, depending on the value of K

c. there is the same amount of hydrogen chloride as there was originally

If the Kp at 2000. K for the reaction given below is 2.1 × 10−3 and the Kp at 27°C is 5.0 × 10−30, calculate ΔH0 for this reaction. A(g) + B(g) C(g) a. 2.6 kJ b. 1.44 J c. −179 kJ d. 180 kJ e. 13.9 kJ

d. 180 kJ

Which statement best represents LeChatelier's Principle? a. A system in equilibrium will always remain in equilibrium. b. Only a change in equilibrium will affect the equilibrium of a reaction. c. When a change is made to a system in equilibrium, equilibrium can never be restored. d. A system in equilibrium will respond to a change by moving in the direction that reduces the change as it returns to equilibrium. e. A system in equilibrium will not be affected by a change in concentration.

d. A system in equilibrium will respond to a change by moving in the direction that reduces the change as it returns to equilibrium.

The Haber process demonstrates that commercial processes do not maximize each factor that affects equilibria but use them in combination to get maximum production. Which of the following statements about the Haber process is false? N2(g) + 3H2(g) 2NH3(g) + 92.24 kJ a. Although Kc is much greater at 25°C, the reaction is carried out at 450°C. b. A catalyst is used to increase reaction rate. c. Although the reaction is exothermic, it is carried out at high (450°C) temperature. d. Although high pressure is unfavorable to the production of the NH3(g), the reaction is carried out under a pressure of 200−1000 atmospheres. e. The emerging reaction mixture is cooled to remove the NH3 and the N2 and H2 recycled.

d. Although high pressure is unfavorable to the production of the NH3(g), the reaction is carried out under a pressure of 200−1000 atmospheres.

Considering the following reaction at equilibrium, identify which of the stresses below would cause more products to form. CO(g) + Cl2(g) COCl2(g) ΔH0 = −113 kJ/mol a. Increase the pressure. b. Increase the [Cl2]. c. Increase the temperature. d. Both (a) and (b) are correct. e. All of these are correct.

d. Both (a) and (b) are correct.

Given the equilibrium reaction: ZnCO3(s) ZnO(s) + CO2(g) Which one of the following statements is true? a. Equal concentrations of ZnO(s) and CO2(g) would result from the decomposition of a given amount of ZnCO3(s). b. The same equilibrium condition would result if we started with only pure ZnCO3(s) in a closed container as if we started with only pure ZnO(s) in a closed container. c. Introducing 1.0 atm pressure of N2(g) into the system at equilibrium in a closed container would result in more ZnCO3(s) being formed. d. Decreasing the volume of the closed system initially at equilibrium, at constant temperature, would result in more ZnCO3(s) being formed. e. At equilibrium conditions, the forward and reverse reactions have stopped.

d. Decreasing the volume of the closed system initially at equilibrium, at constant temperature, would result in more ZnCO3(s) being formed.

If the system below is at equilibrium in a closed vessel and a small amount of nitrous acid is added, what would be expected to happen? HN3 + 2H2O N2H4 + HNO2 ΔH0 = +641 kJ hydrazoic acid hydrazine nitrous acid a. Some HN3 would be used up in re-establishing equilibrium. b. Some HNO2 would be formed in re-establishing equilibrium. c. Some HNO2 would be formed, and some N2H4 would be lost. d. More HN3 and H2O would be formed. e. The temperature would decrease, and the forward reaction would be favored.

d. More HN3 and H2O would be formed.

The following reaction is initiated and the concentrations are measured after ten minutes: A(g) + 3 B(g) AB3(g) Kc = 1.33 × 10−2 [A] = 1.78 M [B] = 2.21 M [AB3] = 1.19 M Is the reaction in equilibrium? a. Yes. b. No, because Q < K. c. No, and the [AB3] must increase to establish equilibrium. d. No, because Q > K. e. There is no way to tell.

d. No, because Q > K.

The equilibrium constant for the following gas phase reaction is 0.50 at 600°C. A mixture of HCHO, H2, and CO is introduced into a flask at 600°C. After a short time, analysis of a small amount of the reaction mixture shows the concentrations to be [HCHO] = 1.5 M, [H2] = 0.5 M, and [CO] = 1.0 M. Which of the following statements about this reaction mixture is true? HCHO H2 + CO a. The reaction mixture is at equilibrium. b. The reaction mixture is not at equilibrium, but no further reaction will occur. c. The reaction mixture is not at equilibrium, but will move toward equilibrium by forming more HCHO. d. The reaction mixture is not at equilibrium, but will move toward equilibrium by using up more HCHO. e. The forward rate of this reaction is the same as the reverse rate.

d. The reaction mixture is not at equilibrium, but will move toward equilibrium by using up more HCHO.

For the following system at equilibrium, H2(g) + CO2(g) H2O(g) + CO(g) the removal of some of the H2O(g) would cause (according to LeChatelier's principle) a. more H2(g) to be form. b. more CO2(g) to be form. c. no change in the amounts of products or reactants. d. more CO(g) to be form. e. the amount of CO(g) to remain constant while the amount of H2O(g) increases to the original equilibrium concentration.

d. more CO(g) to be form.

When the system A + B C + D is at equilibrium, a. the forward reaction has stopped. b. the reverse reaction has stopped. c. both the forward and the reverse reactions have stopped. d. neither the forward nor the reverse reaction has stopped. e. the sum of the concentrations of A and B must equal the sum of the concentrations of C and D.

d. neither the forward nor the reverse reaction has stopped.

Which of the following will require the least time for a reaction to reach equilibrium? a. Kc is a very small number. b. Kc is a very large number. c. Kc is approximately one. d. Cannot tell without knowing the value of Kc. e. Cannot tell, since the time required to reach equilibrium does not depend on Kc.

e. Cannot tell, since the time required to reach equilibrium does not depend on Kc.

Consider the equilibrium decomposition of ammonium bromide. NH4Br(s) NH3(g) + HBr(g) Once equilibrium is established, which of the following would cause this reaction to favor the products more? a. Increase the total pressure. b. Increase the amount of NH4Br. c. Decrease the amount of NH4Br. d. Increase PHBr. e. Decrease PNH2 .

e. Decrease PNH2.

Consider the following reversible reaction at equilibrium. N2(g) + 3H2(g) 2NH3(g) + 9.22 × 104 J Which response contains all the choices below that refer to changes that would shift the equilibrium to the right, and no other choices? I. add H2 II. remove N2 III. add an iron catalyst IV. increase the temperature at constant pressure V. increase the pressure at constant temperature by decreasing the volume a. III, IV and V b. I, IV and V c. IV and V d. I, II and III e. I and V

e. I and V

For the following reaction, which of the changes listed below would cause more reactants to form when equilibrium is re-established? 2NOCl(g) + 75 kJ 2NO(g) + Cl2(g) a. Add a catalyst. b. Increase the temperature. c. Decrease the [NO] d. Increase the volume. e. Increase the pressure.

e. Increase the pressure.

At equilibrium a 1.0-liter container was found to contain 0.20 mol of A, 0.20 mol of B, 0.40 mol of C, and 0.40 mol of D. If 0.10 mol of A and 0.10 mol of B are added to this system, which of the following statements is true? A(g) + B(g) C(g) + D(g) a. The system remains in equilibrium. b. Q > Kc c. More reactants are formed to increase the value of Q. d. The value of Kc decreases. e. More products are formed to increase the value of Q.

e. More products are formed to increase the value of Q.

Which of the statements concerning equilibrium is false? a. A system that is disturbed from an equilibrium condition responds in a manner to restore equilibrium. b. Equilibrium in molecular systems is dynamic, with two opposing processes balancing one another. c. The value of the equilibrium constant for a given reaction mixture is the same regardless of the direction from which equilibrium was attained. d. A system moves spontaneously toward a state of equilibrium. e. The equilibrium constant usually is independent of temperature.

e. The equilibrium constant usually is independent of temperature.

Which of the following statements about ΔG0 and the thermodynamic equilibrium constant is false? a. ΔG0 and K are both indicators of the direction of a spontaneous reaction. b. When ΔG0 < 0, the forward reaction is favored. c. When K < 1, the reverse reaction is favored. d. There is a mathematical relationship between ΔG0 and K. e. When ΔG0 < 0, K < 1.

e. When ΔG0 < 0, K < 1.

Decreasing the volume of the container (at constant temperature) after the system below has reached equilibrium would be expected to ____. HN3 + 2H2O N2H4 + HNO2 a. produce more HN3 and raise the temperature b. produce more H2O and lower the temperature c. produce more N2H4 and raise the temperature d. produce more HNO2 and lower the temperature e. have no effect on this equilibrium

e. have no effect on this equilibrium