Equilibrium Multiple Choice - Killarney Secondary Schoolkillarney.vsb.bc.ca/pope/chem/EquilibriumMC.doc · Web viewWhich of the following describes the changes in the reverse reaction

Equilibrium Multiple Choice

January 1999

7. Consider the following graph:

When equilibrium is reached, the rate of the forward reaction is

A. 0.00 mol/minB. 0.25mol/minC. 1.0 mol/minD. 3.0 mol/min

8. Consider the following equilibrium:2NO2 (g) N2O4 (g) + energy

The equilibrium will shift to the left as a result of

A. adding a catalyst.B. increasing the volume.C. removing some N2O4.D. decreasing the temperature.

9. Ethene, C2H4, can be produced in the following industrial system:C2H6 (g) + energy C2H4 (g) + H2 (g)

The conditions that are necessary to maximize the equilibrium yield of C2H4 are

A. low temperature and low pressure.B. low temperature and high pressure.C. high temperature and low pressure.D. high temperature and high pressure.

10. Consider the following equilibrium:H2 (g) + I2 (g) 2HI (g)

The volume of the equilibrium system is increased and a new equilibrium is established.Compared to the rates in the original equilibrium, which of the following describes the rates of the forward and reverse reactions in the new equilibrium?

11. Consider the following equilibrium:N2 (g) + 3H2 (g) 2NH3 (g) + energy

Certain conditions provide less than 10% yield of NH3 at equilibrium. Which of the following describes this equilibrium?

12. Which of the following best describes the relationship between Keq and temperaturefor an endothermic reaction?

April 1999

7. Consider the following PE diagram for a reversible reaction:

Which of the following describes this reaction?

8. Consider the following equilibrium:2NO(g) + Br2(g) + energy 2NOBr(g)


A. adding a catalyst.B. removing NOBr.C. increasing the volume.D. increasing the temperature.

9. Consider the following equilibrium:N2(g) + O2(g) + energy 2NO(g)

When the temperature is increased, the equilibrium shifts to the

A. left and Keq increases.B. left and Keq decreases.C. right and Keq increases.D. right and Keq decreases.

10. Consider the following equilibrium:2CO(g) + O2(g) 2CO2 (g) + energy

Some CO2 is added to the equilibrium system at constant volume and a new equilibriumis established. Compared to the original equilibrium, the rates of the forward and reversereactions for the new equilibrium have

11. An indication that an equilibrium system favours the products is a

A. large Keq .B. positive H.C. one step mechanism.D. low activation energy.

12. The relationship between Keq and the pressure of a gaseous equilibrium at constant temperature can be described by

13. Consider the following equilibrium:2NO2(g) N2O4(g)

A 1.00 L flask contains 0.030 mol NO2 and 0.040 mol N2O4 at equilibrium.The value of Keq is

A. 0.023B. 0.67C. 1.3D. 44

June 1999

7. Consider the following reaction:N2(g) + 3H2(g) 2NH3 (g) + energy

Which of the following describes the changes in enthalpy and entropy as the reaction proceeds?

8. Consider the following equilibrium:2SO2(g) + O2(g) 2SO3(g) + energy

Which of the following will cause this equilibrium to shift to the left?

A. adding a catalystB. adding some SO2

C. increasing the volumeD. decreasing the temperature

9. Methanol, CH3OH, can be produced by the following:CO(g) + 2H2(g) CH3OH(g) + energy

The conditions that are necessary to maximize the equilibrium yield of CH3OH are

A. low temperature and low pressure.B. high temperature and low pressure.C. low temperature and high pressure.D. high temperature and high pressure.

10. A catalyst is added to a system already at equilibrium. How are the forward and reverse reaction rates affected by the addition of the catalyst?

11. Consider the following reaction:2H2(g) + O2(g) 2H2O(l)

What is the equilibrium constant expression for the reaction?

A. Keq = [H2]2[O2]

[H2]2[O2]B. Keq= ---------------

[H2O]2

[H2O]2

C. Keq= --------------- [H2]2[O2]

1D. Keq= ------------------

[H2]2[O2]

12. The relationship between Keq and temperature for an exothermic reaction is represented by

13. Consider the following equilibrium:2NOBr(g) 2NO(g) + Br2(g) Keq = 6.4 X 10-2

At equilibrium, a 1.00 L flask contains 0.030 mol NOBr and 0.030 mol NO.How many mol Br2 are present?

A. 1.9 103 molB. 6.4 102 molC. 3.0 102 molD. 4.7 101 mol

August 1999

7. At different conditions, the relationship between the forward and reverse rates of reaction in an equilibrium system can be represented by

8. Consider the following equilibrium:4NH3(g) + 5O2(g) 4NO(g) + 6H2O (g) + energy

Which of the following will cause the equilibrium to shift to the left?

A. adding H2O(g)

B. removing some NO (g)

C. increasing the volumeD. decreasing the temperature

9. Consider the following equilibrium:2NO(g) + O2(g) 2NO2 (g) + energy

When the volume of the container is increased, the equilibrium shifts to the

A. left and Keq decreases.B. right and Keq increases.C. left and Keq remains constant.D. right and Keq remains constant.

10. Consider the following equilibrium:4HCl (g) + O2(g) 2H2O(g) + 2Cl2 (g) + energy

The temperature of the equilibrium system is increased and a new equilibrium is established. The rates of the forward and reverse reactions for the new equilibrium compared to the original equilibrium have

11. Consider the following reaction:2Hg(g) + O2(g) 2HgO(s)

The equilibrium constant expression for the reaction is

12. The value of Keq changes when

A. a catalyst is added.B. the temperature changes.C. the surface area changes.D. the concentration of reactants changes.

13. Consider the following equilibrium:PCl5(g) PCl3(g) + Cl2(g)

A 1.00 L flask contains 0.0200 mol PCl5, 0.0500 mol PCl3 and 0.0500 mol Cl2 atequilibrium. The value of Keq is

A. 0.125B. 2.50C. 5.00D. 8.00

January 2000

7. Consider the following equilibrium:N2(g) + 2O2(g) 2NO2(g)

Equal moles of N2 and O2 are added, under certain conditions, to a closed container. Which of the following describes the changes in the reverse reaction which occur as the system proceeds toward equilibrium?

8. A chemical equilibrium is described as “dynamic” because

A. maximum randomness has been achieved.B. the pressure and temperature do not change.C. both reactants and products continue to form.D. the concentrations of chemical species remain constant.

9. Which of the following reactions results in an entropy increase?

A. 2C(s) + O2(g) 2CO(g)

B. N2(g) + 2H2(g) N2H4(l)

C. 2SO2(g) + O2(g) 2SO3(g)

D. Ag+ (aq) + Cl- (aq) AgCl(s)

10. Consider the following equilibrium:CH3COOH(aq) + H2O(l) CH3COO- (aq) + H3O+ (aq) + heat

A stress was applied at time t1 and the data was plotted on the following graph:

The stress that was imposed at time t1 is the result of

A. the addition of HCl.B. decreasing the temperature.C. the addition of NaCH3COO.D. increasing the volume of the container.11. Consider the following potential energy diagram for an equilibrium system:

When the temperature of the system is increased, the equilibrium shifts to the

A. left and the Keq increases.B. left and the Keq decreases.C. right and the Keq increases.D. right and the Keq decreases.

12. What is the Keq expression for the following equilibrium?3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g)

13. Consider the following equilibrium:2O3(g) 3O2(g) Keq= 65

Initially, 0.10 mole of O3 and 0.10 mole of O2 are placed in a 1.0L container. Which of the following describes the changes in concentrations as the reaction proceeds toward equilibrium?

April 2000

7. Which of the following applies to a chemical equilibrium?

I. Forward and reverse reaction rates are equalII. Equilibrium can be achieved from either directionIII. Macroscopic properties are constant

A. I onlyB. I and II onlyC. II and III onlyD. I, II and III

8. In which of the following will the driving forces of minimum enthalpy and maximum entropy oppose one another?

A. 2C(s) + O2(g) 2CO(g) H= -221kJB. 2N2(g) + O2(g) 2N2O(g) H= +164kJC. 2CO(g) + O2(g) 2CO2(g) H= -566kJD. 2CO2(g) + 6H2O(g) 2C2H6(g) + 7O2(g) H= +3122kJ

9. Consider the following equilibrium:2CrO4 2- (aq) + 2H3O+ (aq) Cr2O7 2- (aq) + 3H2O(l)

(yellow) (orange)

An unknown solution is added to an orange equilibrium sample until the sample turns yellow. The unknown solution could be

A. KNO3

B. NaOHC. NH4NO3

D. CH3COOH

10. Ammonia, NH3 , is produced by the following reaction:N2(g) + 3H2(g) 2NH3(g) + energy

Which of the following would result in the highest concentration of ammonia at equilibrium?

A. increasing the temperature and increasing the pressureB. decreasing the temperature and increasing the pressureC. increasing the temperature and decreasing the pressureD. decreasing the temperature and decreasing the pressure

11. What is the Keq expression for the following reaction?

SnO2(s) + 2CO(g) Sn(s) + 2CO2(g)

12. Consider the following reaction:C(s) + 2H2(g) CH4(g) H = -74.8KJ

Which of the following will cause an increase in the value of Keq?

A. increasing [H2]B. decreasing the volumeC. finely powdering the C (s)

D. decreasing the temperature

13. Consider the following equilibrium:H2(g) + I2(g) 2HI(g)

At equilibrium [H2] = 0.00220 mol/L, [I2] = 0.00220 mol/L and [HI] = 0.0156mol/L. The value of Keq is

A. 3.10 X 10-4

B. 1.99 X 10-2

C. 5.03 X 101

D. 3.22 X 103

June 2000

7. Consider the following equilibrium:2NOCl(g) 2NO(g) + Cl2(g)

A flask of fixed volume is initially filled with NOCl(g), NO(g) and Cl2(g) . When equilibrium is reached, the pressure has increased. To reach equilibrium, the reaction proceeded to the

A. left because Trial Keq was less than Keq.B. right because Trial Keq was less than Keq.C. left because Trial Keq was greater than Keq .D. right because Trial Keq was greater than Keq .8. In which of the following do both minimum enthalpy and maximum entropy factorsfavour the reactants?

A. Cl2(g) Cl2(aq) H= -25 kJB. C(s) + H2O(l) CO(g) + H2(g) H= +131kJC. 2CO2(g) + 3H2O(g) C2H5OH(l) + 3O2 H= +1239kJD. Na2CO3(s) + HCl (aq) 2NaCl (aq) + CO2(g) + H2O(l) H= -28kJ

9. Consider the following equilibrium:H2 (g) + I2(g) 2HI(g)

Which graph represents what happens when some HI is removed and a new equilibrium is established?

10. Consider the following equilibrium:CO(g) + H2O(g) CO2(g) + H2(g) H= -41kJ

What will cause a shift in the equilibrium?

A. adding a catalystB. changing volumeC. adding an inert gasD. changing temperature

11. The equilibrium expression for a reaction is

[H+]6

Keq = ------------------- [Bi3+]2[H2S]3

The reaction could be

A. 6H+ + BiS(s) 2Bi 3+ (aq) + 3H2S(g)

B. 6H+ (aq) + Bi2S3 (s) 2Bi 3+ (aq) + 3H2S(g)

C. 2Bi 3+ (aq) + 3H2S (aq) Bi2S3(s) + 6H+(aq)

D. 2Bi 3+ (aq) + 3H2S (aq) Bi2S3 (aq) + 6H+ (aq) 12. Consider the following equilibrium:

Co(H2O)6 2+ (aq) + 4Cl- CoCl4

2- (aq) + 6H2O(l)

(pink) (blue)When the temperature is increased, the solution turns a dark blue. Based on this observation, the reaction is

A. exothermic and the Keq has increased.B. exothermic and the Keq has decreased.C. endothermic and the Keq has increased.D. endothermic and the Keq has decreased.

13. Consider the following equilibrium:2O3(g) 3O2(g) Keq = 36

What is the concentration of O3 when the equilibrium concentrationOf O2 is 6.0 X 10-2 mol/L?

A. 2.4 X 10-3 mol/LB. 4.0 X 10-2 mol/LC. 6.0 X 10-2 mo/LD. 9.0 X 10-2 mol/L

August 2000

7. Which of the following does not apply to all chemical equilibrium systems?

A. They are closed.B. The macroscopic properties are constant.C. Forward and reverse reaction rates are equal.D. There are equal concentrations of reactants and products.

8. Consider the following equilibrium:2NOCl(g) 2NO (g) + Cl2(g)

A flask is filled with NOCl, NO and Cl2. Initially there was a total of 5.0 moles ofgases present. When equilibrium is reached, there is a total of 6.0 moles of gases present.Which of the following explains this observation?

A. The reaction proceeded left because the Trial Keq > KeqB. The reaction proceeded left because the Trial Keq < KeqC. The reaction proceeded right because the Trial Keq > KeqD. The reaction proceeded right because the Trial Keq < Keq

9. Consider the following reaction:

C3H8 (g) + 5O2(g) 3CO2(g) + 4H2O(g) H = -2202kJWhich of the following applies to the forward reaction?

Entropy Enthalpy A. increases increasesB. increases decreasesC. decreases increasesD. decreases decreases

10. Consider the following equilibrium:2NO2(g) N2O4 (g) + energy

The number of moles of NO2 at equilibrium could be increased by

A. adding N2O4

B. adding a catalyst.C. decreasing the temperature.D. decreasing the volume by increasing the pressure.

11. What is the Keq expression forSb3+

(aq) + Cl-(aq) + H2O(l) SbOCl (s) + 2H+ (aq)

12. Consider the following equilibrium:H2 (g) + I2(g) 2HI(g) Keq = 50.0

What is the value Keq for the reaction rewritten as:2HI (g) H2(g) + I2(g) Keq = ?

A. –50.0B. 0.0200C. 25.0D. 50.0

13. Consider the following equilibrium:2NO2(g) N2O4 (g) Keq = 1.15

The equilibrium concentration of NO2 is 0.50 mol/L. Calculate the equilibriumConcentration of N2O4 (g).

A. 0.22 mol/LB. 0.29 mol/LC. 0.43 mol/LD. 0.58 mol/L

January 2001

7. All chemical equilibriums have:

I. rates that are continuing to changeII. an equilibrium constant expressionIII. equal concentrations of products and reactants

A. II onlyB. III onlyC. I and II onlyD. I and III only

8. From the following, select the situation where both enthalpy and entropy favourthe reaction toward products:

Enthalpy Entropy A. increasing increasingB. increasing decreasingC. decreasing decreasingD. decreasing increasing

9. Consider the following equilibrium:2NO(g) + Br2(g) 2NOBr(g) + energy


A. adding a catalyst.B. adding some NO (g).

C. increasing the volume.D. decreasing the temperature.

10. Consider the following equilibrium:PCl3(g) + 3NH3(g) P(NH2)3 (g) + 3HCl(g)

The volume of the equilibrium system is increased and a new equilibrium is established.

How have the rates been affected?

Rate (forward) Rate (reverse) A. increased decreasedB. decreased increasedC. decreased decreasedD. did not change did not change

11. Starting with equal moles of reactants, which of the following equilibrium systemsmost favours the reactants?

A. SO2(g) + NO2(g) SO3 (g) + NO(g) Keq= 3.4B. CO(g) + H2O(g) CO2(g) + H2(g) Keq= 31.4C. H2(g) + I2(g) 2HI(g) Keq= 10D. N2 (g) + O2(g) 2NO(g) Keq= 1.0X10-31

12. Consider the following equilibrium reaction:N2O4(g) 2NO2(g)

At time t1, heat is applied to the system. Which of the following best describes theequilibrium reaction and the change in Keq?

A. exothermic and Keq increasesB. exothermic and Keq decreasesC. endothermic and Keq increasesD. endothermic and Keq decreases

13. Consider the following:

PCl3(g) + Cl2(g) PCl5(g) Keq = 0.45 at 227°C

Initially, a 1.00L flask is filled with 0.100mol PCl3, 0.100mol Cl2, and 0.100mol PCl5

at 227°C. Use KTrial to predict the change in [Cl2] as equilibrium is established.

April 2001

7. Consider the following equilibrium reaction:2ICl(g) I2(g) + Cl2(g)

Some ICl is added to an empty flask. How do the reaction rates change asthe system approaches equilibrium?

Forward rate Reverse rate A. increases increasesB. increases decreasesC. decreases increasesD. decreases decreases

8. In an equilibrium system, continuing microscopic changes indicate that the equilibrium is

A. dynamic.B. complete.C. exothermic.D. spontaneous.

9. Consider the following equilibrium:4CuO(s) + energy 2Cu2O(s) + O2(g)

The equilibrium will shift to the right as a result of

A. adding CuO (s).

B. removing O2 (g).

C. adding a catalyst.D. decreasing the temperature.

10. Consider the following equilibrium:N2(g) + 3H2(g) 2NH3(g)

The volume of the system is decreased. The equilibrium shifts

A. left since the reverse rate is greater than the forward rate.B. left since the forward rate is greater than the reverse rate.C. right since the reverse rate is greater than the forward rate.D. right since the forward rate is greater than the reverse rate.

11. Consider the following equilibrium:

2SO3(g) 2SO2(g) + O2(g) kJWhen the temperature is increased, the equilibrium will shift

A. left with Keq becoming larger.B. right with Keq becoming larger.C. left with Keq becoming smaller.D. right with Keq becoming smaller.

12. Starting with equal concentrations of reactants, which of the following will beclosest to completion at equilibrium?

A. CO(g) + Cl2(g) COCl2(g) Keq=22B. PCl3(g) + Cl2(g) PCl5(g) Keq= 2.9 X 10-2

C. CO(g) + Cl2(g) COCl2(g) Keq=4.5 X 10 –9

D. CH3O2 (g) + NO2(g) CH3O2NO2(g) Keq=2.1 X 10 -12

13. Consider the following equilibrium:2COF2(g) CO2(g) + CF4(g)

At equilibrium, a 1.00L container contains 7.07 X 10-4 mol COF2, 1.00 X 10-3 mol CO2, and 1.00 X 10-3 mol CF4. What is the value of Keq?

A. 7.07 X 10-4

B. 1.41 X 10-3

C. 0.500D. 2.00

June 2001

7. Consider the following reaction:2ICl(g) I2(g) + Cl2(g)

A closed container is initially filled with ICl (g). What are the changes in therate of the forward reaction and [I2], as the system approaches equilibrium?

8. The entropy of a system is a term used to describe

A. randomness.B. heat content.C. average kinetic energy.D. stored chemical energy.

9. Consider the following equilibrium:Cu2+

(aq) + 4Br-(aq) + energy CuBr4 2-

(aq) Blue colourless green

Which of the following will cause this equilibrium to change from blue to green?

A. adding NaBr (s)

B. adding NaNO3 (s)

C. adding a catalystD. decreasing the temperature

10. Consider the following equilibrium:Ni(s) + 4CO(g) Ni(CO)2(l) kJ

Which of the following will cause this equilibrium to shift to the left?

A. add some COB. decrease the volumeC. remove some Ni(CO)4

D. increase the temperature

11. Consider the following equilibrium:N2O4(g) + energy 2NO2(g)

Which of the following shows the relationship between concentration and timeas a result of adding a catalyst at time t = 1?

12. Consider the following equilibrium:H2S(g) + I2(s) 2HI(g) + S(s)

What is the equilibrium expression for this reaction?

[HI]2

A Keq=--------------- [H2S]

[H2S]B. Keq=---------------

[HI]2

[HI]2[S]C. Keq=---------------

[H2S]P[I2]

[H2S]P[I2]D. Keq=---------------

[HI]2[S]

13. Consider the following equilibrium:CO(g) + H2O(g) CO2(g) + H2(g) Keq = 5.0

At equilibrium, the [CO]= 0.20mol/L, [H2O]= 0.30mol/L, and [H2]= 0.90mol/L. Calculate the equilibrium [CO2].

A. 0.013 mol/L C. 0.33 mol/LB. 0.066 mol/L D. 1.0mol/L14. Consider the following:

CO2(g) + CF4(g) 2COF2(g) Keq= 0.50

In a reaction container the initial concentrations are:[CO2]= 0.50mol/L, [CF4]= 0.50mol/L, [COF2]= 0.30 mol/L

To reach equilibrium, the reaction will proceed

A. left since Trial Keq < K eq

B. left since Trial Keq > K eq

C. right since Trial Keq < K eq

D. right since Trial Keq > K eq

August 2001

7. All chemical equilibriums must have

A. Keq = 1B. [reactants]=[products].C. rate forward = rate reverse.D. mass of reactants = mass of products.

8. Consider the following equilibrium reaction:4HCl(g) + O2(g) 2H2O(g) + 2Cl2(g) + 111.4kJ

For the forward reaction, how do enthalpy and entropy change?

Enthalpy Entropy A. increases decreasesB. decreases decreasesC. increases increasesD. decreases increases

9. Consider the following equilibrium:CH3Cl(aq) + OH- (aq) CH3OH(aq) + Cl-

(aq)

The equilibrium will shift to the left as a result of the addition of

A. HNO3

B. KNO3

C. NaOHD. CH3Cl

10. Consider the following equilibrium at 25°C :

Ni(s) + 4CO(g) Ni(CO)4(l)

For this reaction

A. Keq = [CO]4

1B. Keq= --------------

[CO]4

[Ni(CO)4(l)]C. Keq= ---------------- [CO]4 [Ni]

[Ni(CO)4(l)]D. Keq= ----------------

[CO]4

11. Consider the following equilibrium:2COF2(g) CO2(g) + CF4(g) Keq=2.00

At equilibrium, [CO2]=0.050mol/L and [CF4]=0.050mol/L. What t is [COF2] at equilibrium?


12. Consider the following equilibrium:H2O(g) + Cl2O(g) 2HOCl(g) Keq= 0.0900

Initially, a 1.00L flask is filled with 0.100mol of H2O, 0.100mol of Cl2O and 0.100mol of HOCl. As equilibrium is established, the reaction proceeds to the

A. left because KTrial > K eqB. left because KTrial < K eqC. right because KTrial > K eqD. right because KTrial < K eq

January 2002

7. Consider the following:2SO2(g) + O2(g) 2SO3(g)

Initially, SO3 is added to an empty flask. How do the rate of the forward reaction and [SO3] change as the system proceeds to equilibrium?

8. Consider the following reaction:N2(g) + 3H2(g) 2NH3(g) + energy

What positions do minimum enthalpy and maximum entropy tend toward?

Use the following equilibrium equation to answer questions 9 and 10.

CO2(g) + H2(g) H2O(g) + CO(g)

9. Which two stresses will each cause the equilibrium to shift to the left?

A. increase [H2] , increase [CO]B. decrease [H2] , increase [H2O]C. increase [CO2] , decrease [CO]D. decrease [CO2] , decrease [H2O]

10. Which of the following graphs represents the forward rate of reaction when H2O(g) is added to the above equilibrium at time t = 1 ?

11. Consider the following:2NH3 (g) N2(g) + 3H2(g)

Initially, some NH3 is placed into a 1.0L container. At equilibrium there is 0.030mol N2

present. What is the [H2] at this equilibrium?


12. Which reaction has the following equilibrium expression?

[NO2]4[H2O]6

Keq=----------------- [NH3]4[O2]7

A. 4NH3(g) + 7O2(g) 4NO2(g) + 6H2O(g)

B. 4NH3(aq) + 7O2(g) 4NO2(aq) + 6H2O(l)

C. 4NO2(aq) + 6H2O(l) 4NH3(g) + 7O2(g)

D. 4NO2(g) + 6H2O(g) 4NH3(g) + 7O2(g)

13. What will cause the Keq for an exothermic reaction to increase?

A. increasing [reactants]B. decreasing [products]C. increasing the temperatureD. decreasing the temperature

April 2002

7. Consider the following:H2(g) + I2(g) 2HI(g)

Initially, HI is added to an empty flask. How do the rates of the forward and reverse reactions change as the system proceeds to equilibrium?

8. Consider the following reaction:2H2O(l) + energy 2H2 (g) + O2(g)

Determine the enthalpy and entropy changes for the above reaction?


2CO(g) + O2(g) 2CO2(g) + energy

9. Which of the following two stresses will each cause the system to shift to the right?

A. increase temperature, increase volumeB. decrease temperature, increase volumeC. increase temperature, decrease volumeD. decrease temperature, decrease volume

10. Which of the following shows the forward rate of reaction when the temperature of the system is increased at time t = 1 ?

11. Consider the following:2SO2(g) + O2(g) 2SO3(g)

Initially, 0.030mol SO2 and 0.030mol O2 are placed into a 1.0L container. At equilibrium, there is 0.020 mol O2 present. What is the [SO2] at equilibrium?


12. What is the equilibrium expression for the following system?CaCO3(s) + 2HF(g) CaF2(s) + H2O(g) + CO2(g)

[HF]2 [H2O][CO2]A. Keq=-------------------- C. Keq= --------------- [H2O][CO2] [CaCO3][HF]2

[H2O][CO2] [CaF2] [H2O][CO2]B. Keq=---------------- D. Keq= ---------------------- [HF]2 [CaCO3][HF]2

13. What will cause the Keq for an endothermic reaction to decrease?

A. adding a catalystB. increasing the surface areaC. increasing the temperatureD. decreasing the temperature

June 2002

7) Consider the following :2HBr(g) ⇄ H2(g) + Br2(g)

Initially, HBr is added to an empty flask. How do the rate of the forward reaction and the [HBr] change as the system proceeds to equilibrium?

Forward Rate [HBr]A. Decreases DecreasesB. Decreases IncreasesC. Increases IncreasesD. Increases Decreases


8) Which of the following two stresses will each cause the system to shift to the right?

A. decrease temperature, decrease [O2]B. increase temperature, increase [SO3]C. increase temperature, decrease [SO3]D. decrease temperature, increase [SO2]

9) Which of the following graphs shows the reverse rate of reaction when a catalyst is added to the equilibrium at time = t1?

2SO2(g) + O2(g) ⇄ 2SO3(g) + energy

10) Consider the following: ?2N2(g) + O2(g) + energy ⇄ 2N2O(g)


MinimumEnthalpy

MaximumEntropy

A. products productsB. products reactantsC. reactants productsD. reactants reactants

11) Consider the following:H2(g) + I2(g) ⇄ 2HI(g)

Initially, some HI is placed into a 1.0L container. At equilibrium there is 0.010 mol H2, 0.010 mol I2 and 0.070 mol HI present. How many moles of HI were initially added to the container?

A. 0.060 molB. 0.070 molC. 0.080 molD. 0.090 mol

12) What is the equilibrium expression for the following system?

4Fe(s) + 3O2(g) ⇄ 2Fe2O3(s)

A. Keq = [O2]3

1B. Keq =

[O2]3

[Fe2O3]2

C. Keq = [Fe]4[O2]3

[2Fe2O3]

D. keq = [4Fe][3O2]

13) What will cause the value of Keq for an endothermic reaction to increase?

A. increasing [products]B. decreasing [products]C. increasing the temperatureD. decreasing the temperature

14) Consider the following equilibrium:

N2O4(g) ⇄ 2NO2(g)

An equilibrium mixture contains 4.0 × 10-2 mol N2O4 and 1.5 × 10-2 mol NO2

In a 1.0L flask. What is the value of Keq?

A. 5.6 × 10-3

B. 3.8 × 10-1

C. 7.5 × 10-1

D. 1.8 × 102

August 2002

7) Consider the following:2NH3(g) ⇄ N2(g) +3H2(g)

Initially, NH3 is added to an empty flask. How do the rates of the forward andReverse reactions change as the system proceeds to equilibrium?

Forward Rate Reverse RateA. Increases IncreaseB. Increases DecreasesC. Decreases IncreasesD. decreases decreases

8) Consider the following: ?

H2(g) + Br2(l) ⇄ 2HBr(g) + energy


Minimum Enthalpy Maximum EntropyA. Products ProductsB. Products ReactantsC. Reactants ProductsD. Reactants Reactants


H2(g) + I2(g) ⇄ 2HI(g) + energy

9) Which of the following stresses will not cause s shift in equilibrium?

A. decrease [I2]B. increase [H2]C. decrease volumeD. increase temperature

10) Which of the following shows the reverse rate of reaction when the volume is decreased at time = t1?

11) Consider the following:2SO3(g) ⇄ 2SO2(g) + O2(g)

Initially, some SO3 is placed into a 3.0L container. At equilibrium there is0.030 mol SO2 present. What is the [O2] at equilibrium?


12) Which reaction has the following equilibrium expression?

[PCl5] Keq = [PCl3][Cl2]

A. PCl3(g) + Cl2(g) ⇄ PCl5(g)

B. PCl3(g) + Cl2(l) ⇄ PCl5(g)

C. PCl5(g) ⇄ PCl3(g) + Cl2(g)

D. PCl5(g) ⇄ PCl3(g) + Cl2(l)

13) What will cause the value of Keq for an exothermic reaction to decrease?

A. increasing the pressureB. increasing the temperatureC. decreasing the temperatureD. decreasing the surface area


H2(g) + I2(g) ⇄ 2HI(g)

An equilibrium mixture contains 1.0 × 10-3 mol H2, 2.0 × 10-3 mol I2 And 1.0 × 10-2 mol HI in a 1.0L container. What is the value of Keq?

A. 2.0 × 10-2

B. 5.0 × 101

C. 50 × 103

D. 1.0 × 104

January 2003

7) Which of the factors below is not a condition necessary for equilibrium?

A. a closed systemB. a constant temperatureC. equal forward and reverse reaction ratesD. equal concentrations of reactants and products

8) In order for a chemical reaction to go to completion, how must the entropy and enthalpy change?

Entropy EnthalpyA. Increases IncreasesB. Increases DecreasesC. Decreases IncreasesD. Decreases Decreases

9) Consider the following equilibrium system:

2SO2(g) + O2(g) ⇄ 2SO3(g) Keq = 1.2 × 104

If additional SO2 is added to the system, what happens to the equilibrium andThe value of Keq?

Equilibrium KeqA. Shifts left DecreasesB. Shifts right IncreasesC. Shifts right No changeD. No change No change


N2(g) + 3H2(g) ⇄ 2NH3(g)

Determine the changes in reaction rates as a catalyst is added.

Forward Rate Reverse RateA. Increases IncreasesB. Increases DecreasesC. Decrease IncreasesD. Decreases Decreases


2KClO3(s) ⇄ 2KCl(s) + 3O2(g)

Which of the following is the equilibrium constant expression?

A. Keq = [O2]3

1B. Keq =

[O2]3

[KClO3]2

C. Keq = [KCl]2[O2]3

[KCl]2[O2]3

D. Keq = [KClO3]2


CO2(g) + 2H2O(g) ⇄ CH4(g) + 2O2(g)

Which of the options below indicates that the reactants are favoured?

A. Keq is aero.B. Keq is very large.C. Keq is slightly less than 1.D. Keq is slightly greater than 1.


N2O4(g) + energy ⇄ 2NO2(g)

How are Keq is [N2O4] affected by the addition of Ne (an inert gas) into theContainer at constant volume.

Keq [N2O4]A. No change No changeB. No change IncreasesC. Increases DecreasesD. decreases increases


Cl2(g) + 2NO(g) ⇄ 2NOCl(g) Keq = 5.0

At equilibrium, [Cl2] = 1.0M and [NO] = 2.0M. What is the [NOCl] at equilibrium?

A. 0.80 MB. 0.89 MC. 4.5 MD. 10 M

April 2003

7) For the equilibrium system below:

Cu(s) + 2Ag+(aq) ⇄ 2Ag(s) + Cu+2

(aq)

We would know the system is at equilibrium because

A. [Cu+2] = [Ag+]B. 2[Cu+2] = [Ag+]C. the mass of Cu(s) remains constant.D. the mass of the entire system remains constant.

8) For the reacting system:

2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g) ∆H = -433 KJ

What will entropy and enthalpy factors favour?

Entropy EnthalpyA. Products ReactantsB. Products ProductsC. Reactants ReactantsD. Reactants Products


N2(g) + 3H2(g) ⇄ 2NH3(g)

If some Ne gas is added at a constant volume then how will [N2], [H2] and Keq

be affected?

[N2] [H2] Keq

A. Increases Increases DecreasesB. Decreases Decreases IncreasesC. Decreases Increases Does not changeD. Does not change Does not change Does not change

10) What is the effect of adding a catalyst to an equilibrium system?

A. The value of Ea increases.B. The value of Keq increases.C. Forward and reverse rates increase.D. The concentration of products increases.


2CrO42-

(aq) + 2H+(aq) ⇄ Cr2O7

2-(aq) + H2O(l)

What is the Keq expression?

[CrO42-]2[H+]2

A. [Cr2O7

2-]

[Cr2O72-]

B. [CrO4

2-]2[H+]2

[Cr2O72-]

C. [2CrO4

2-][2H+]

[Cr2O72-][H2O]

D. [CrO4

2-]2[H+]2

12) A container is initially filled with pure SO3. After a period of time, the following equilibrium is established:

2SO2(g) + O2(g) ⇄ 2SO3(g) Keq = 7.0 × 1025

What does this equilibrium mixture contain?

A. mostly products

B. mostly reactants

3 2C. reactants and products

5 5

D. equal amounts of reactants and products.


2CO(g) + O2(g) ⇄ 2CO2(g) Keq = 4.0 × 10-10

What is the value of Keq for 2CO2(g) ⇄ 2CO(g) + O2(g) ?

A. 4.0 × 10-10

B. 2.0 × 10-5

C. 5.0 × 104

D. 2.5 × 109


H2(g) + Br2(g) ⇄ 2HBr(g) ∆H = -36KJ

How could the value of Keq be increased?

A. add H2

B. add HBrC. increase the pressureD. reduce the temperature

June 2003

7) Consider the following PE diagram:

Identify the activation energy for the forward uncatalysed reaction.

A. 1B. 2C. 3D. 4

8) In which of the following will entropy and enthalpy factors favour the establishment of an equilibrium?

?

A. CaCO3(s) + 178KJ → CaO(s) + CO2(g)

?

B. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) + 425KJ ?

C. 2C(s) + 2H2(g) → C2H4(g) ∆H = +52.3KJ ?

D. 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g) ∆H = -1560 KJ


CO(g) + 2H2(g) ⇄ CH3OH(g) ∆H = -91KJ

Which of the factors below would increase the concentration ofCH3OH at equilibrium?

A. an addition of COB. an increase in the volumeC. a decrease in the pressureD. an increase in the temperature

10) Consider the following equilibrium:PCl3(g) + Cl2(g) ⇄ PCl5(g)

If the volume of the system is decreased, how will the reaction rates in the new

equilibrium compare with the rates in the original equilibrium?

Forward Rate Reverse RateA. Increases IncreasesB. Increases DecreasesC. Decreases DecreasesD. Decreases Increases

11) Consider the following equilibrium:H2(g) + I2(g) ⇄ 2HI(g) ∆H = -71.9KJ

Colourless purple colourless

Which of the following would allow you to conclude that the system has reached equilibrium?

A. The pressure remains constant.B. The reaction rates become zero.C. The colour intensity remains constant.D. The system shifts completely to the right.

12) Consider the following equilibrium:Fe2O3(s) + 3CO(g) ⇄ 2Fe(s) + 3CO2(g)

Identify the equilibrium constant expression.

[CO2]3

A. Keq = [CO]3

[CO2]B. Keq =

[CO]

[CO2]3[Fe]2

C. Keq = [Fe2O3][CO]3

[Fe2O3][CO]3

D.Keq = [CO2]3[Fe]2


2NO(g) + Cl2(g) ⇄ 2NOCl(g) ∆H = -77KJ

In which direction will the equilibrium shifts and what happens to the value of

Keq when the temperature of the system is increased?

Shift KeqA. Right IncreasesB. Right DecreasesC. Left IncreasesD. Left Decreases


CO(g) + 2H2(g) ⇄ CH3OH(g)

At equilibrium it was found that [CO] = 0.105 mol/L, [H2] = 0.250 mol/L and[CH3OH] = 0.00261 mol/L. Which of the following is the equilibrium constantvalue?

A. 9.94 × 10-2

B. 0.398C. 2.51D. 10.0

August 2003


H2(g) + I2(g) ⇄ 2HI(g)

How will the forward and reverse equilibrium reaction rates change whenadditional H2 is added to the system?

Forward Rate Reverse RateA. Increase IncreaseB. Increase DecreaseC. Decrease IncreaseD. No change No change

8) Consider the following system at equilibrium:

H2O(g) + CO(g) ⇄ CO2(g) + H2(g)

This equilibrium will shift right as the result of the addition of some extra H2O.How will this shift affect the concentrations of the other gases?

[CO] [CO2] [H2]A. Increases Decreases DecreasesB. Increases Increases DecreasesC. Decreases Increases IncreasesD. Deceases Decreases Increases


N2(g) + 3H2(g) ⇄ 2NH3(g)

Which of the following factors will not alter the position of equilibrium?

A. a pressure decreaseB. a temperature increaseC. the presence of a catalystD. the addition for more N2(g)


N2O4(g) + energy ⇄ 2NO2(g)

Which of the following graphs shows the result of increasing the temperature at time t1?

11) Consider the following equilibrium and the table of experimental data:N2O4(g) ⇄ 2NO2(g)

Initial Equilibrium

[N2O4] [NO2] [N2O4] [NO2]

Trial 1 0.0400 0.0000 0.0337 0.0125Trial 2 0.0200 0.0600 0.0429 0.0141

Which of the following represents the Keq value?

A. 4.64 × 10-3

B. 3.71 × 10-1

C. 7.42 × 10-1

D. 2.16 × 102

12) Which of the following is least likely to favour the formation of products?

A. 2H2O(g) ⇄ 2H2(g) + O2(g) Keq = 7.3 × 10-18

B. N2O(g) + NO2(g) ⇄ 3NO(g) Keq = 4.2 × 10-4

C. N2O4(g) ⇄ 2NO2(g) Keq = 4.5D. SO2(g) + NO2(g) ⇄ NO(g) + SO3(g) Keq = 85

13) Consider the following equilibrium:N2(g) + 3H2(g) ⇄ 2NH3(g)

What is the final result of adding some NH3 gas to the system at constant volume?

A. Keq increases.B. [H2] decreases.C. [NH3] decreases.D. Keq remains unchanged.

14) Consider the following system:2CO(g) + O2(g) ⇄ 2CO2(g)

A container is initially filled with CO and O2. How will the [CO] and [CO2]change as the system reaches equilibrium?

[CO] [CO2]A. Increase DecreaseB. Increase IncreaseC. Decrease DecreaseD. decrease increase

Answer Key

January 1999 April 1999 June 1999 August 19997 C 7 D 7 C 7 A8 B 8 C 8 C 8 A9 C 9 C 9 C 9 C10 A 10 A 10 A 10 A11 D 11 A 11 D 11 A12 C 12 D 12 A 12 B13 C 13 D 13 B 13 A

January 2000 April 2000 June 2000 August 20007 A 7 D 7 B 7 D8 C 8 C 8 C 8 D9 A 9 B 9 B 9 B10 C 10 B 10 D 10 A11 B 11 B 11 C 11 A12 C 12 D 12 C 12 B13 B 13 C 13 A 13 B

January 2001 April 2001 June 2001 August 20017 A 7 C 7 A 7 C8 D 8 A 8 A 8 B9 C 9 B 9 A 9 A10 C 10 D 10 D 10 B11 D 11 B 11 C 11 B12 C 12 A 12 A 12 A13 A 13 D 13 C

14 C

January 2002 April 2002 June 2002 August 20027 D 7 B 7 A 7 C8 D 8 C 8 D 8 A9 B 9 D 9 B 9 C10 C 10 B 10 D 10 C11 D 11 A 11 D 11 A12 A 12 B 12 B 12 A13 D 13 D 13 C 13 B

14 A 14 B

January 2003 April 2003 June 2003 August 20037 D 7 C 7 B 7 A8 B 8 B 8 A 8 C9 C 9 D 9 A 9 C10 A 10 C 10 A 10 A11 A 11 B 11 C 11 A12 C 12 A 12 A 12 A13 A 13 D 13 D 13 D14 C 14 D 14 B 14 D

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Equilibrium Multiple Choice - Killarney Secondary Schoolkillarney.vsb.bc.ca/pope/chem/EquilibriumMC.doc · Web viewWhich of the following describes the changes in the reverse reaction