Deck 14: Chemical Equilibrium Equal but Opposite Reaction Rates

Question 1

Which statement below regarding the equilibrium constant is FALSE?

A)When K $\gg$ 1, the concentrations of products are much greater than the concentrations of reactants at equilibrium.
B)When K $\ll$ 1, the concentrations of reactants are much greater than the concentrations of products at equilibrium.
C)When K = 1, the concentrations of products and reactants at equilibrium are equal.
D)When K = 1, the forward and reverse rate constants are equal.
E)When K $\gg$ 1, the products and reactants come to equilibrium rapidly.

Answer 1

When K $\gg$ 1, the products and reactants come to equilibrium rapidly.

Question 2

For the equilibrium 2HI(g) ⇄ H₂ (g) + I₂ (g), the equilibrium constant at 700 K is approximately 1.75 * 10^-2 and the rate constant of the forward reaction is approximately 1.16*10^-3 M ^-1 s^-1.What is the value of the reverse rate constant?

A)6.63 *10^-2 M ^-1 s^-1
B)1.51* 10¹ M ^-1 s^-1
C)1.16 *10^-3 M ^-1 s^-1
D)2.03 * 10^-5 M ^-1 s^-1
E)1.00 M ^-1 s^-1

Answer 2

6.63 *10^-2 M ^-1 s^-1

Question 3

Which statement below regarding the law of mass action and the mass action expression is FALSE?

A)The law of mass action defines the equilibrium constant to be the ratio of the forward and reverse rate constants for a particular equilibrium expression.
B)The law of mass action states that the ratio of product concentrations to reactant concentrations, raised to powers equal to their coefficients in a balanced chemical reaction, has a characteristic value at a given temperature.
C)The mass action expression is equivalent to the equilibrium expression in form but may be applied to reaction mixtures that are not at equilibrium.
D)At a given temperature, the characteristic ratio of products to reactants at equilibrium will be the same regardless of the composition of the starting mixture.
E)At a given temperature, the equilibrium concentrations of products and reactants depend on the composition of the starting mixture.

Answer 3

The law of mass action defines the equilibrium constant to be the ratio of the forward and reverse rate constants for a particular equilibrium expression.

Question 4

For the equilibrium NO₂ (g) +O₂ (g) ⇄ NO(g) +O₃ (g), the equilibrium constant at 300.0 K is approximately 2.9*10^-35 and the rate constant of the reverse reaction is approximately 8.5 *10⁶ M ^-1 s^-1.What is the value of the forward rate constant?

A)2.1 * 10^-21 M ^-1 s^-1
B)3.4 *10^-42 M ^-1 s^-1
C)2.5 * 10^-28 M ^-1 s^-1
D)4.1 *10²⁷ M ^-1 s^-1
E)1.0 M ^-1 s^-1

Question 5

A chemical equilibrium may be established by starting a reaction with

A)reactants only.
B)products only.
C)equal quantities of reactants and products.
D)any quantities of reactants and products.
E)all of the above

Question 6

The equilibrium constant for the acid ionization of mercaptoethanol (HSCH₂CH₂OH ) is 1.91 *10^-10.HSCH₂CH₂OH(aq) ⇄ H⁺ (aq) +SCH₂CH₂OH^-(aq).Which statements) regarding this equilibrium is/are true? I.The reaction is product favored.
II.The reaction is reactant favored.
III.Equilibrium lies far to the right.
IV.Equilibrium lies far to the left.

A)I and III
B)I and IV
C)II and III
D)II and IV
E)None are true, as the concentrations of reactants and products are comparable.

Question 7

Consider the equilibrium A +B ⇄ C.What is significant about the equilibrium state in which [B] = [C]?

A)[A]= K
B)[A] =[B] = [C]
C)[B] = [C] = K
D)[A] = 1/K
E)[C]/[B] = K

Question 8

The forward rate constant, k_f, and reverse rate constant, k_r, for a chemical reaction are not equal.Which statement below must be true?

A)The reaction will be unable to achieve equilibrium.
B)k_f and k_r will become equal as equilibrium is approached owing to concentration changes.
C)k_f and k_r will become equal as equilibrium is approached owing to temperature changes.
D)k_f and k_r will remain unequal, but the rates will become equal owing to concentration changes.
E)k_f and k_r will remain unequal, but the rates will become equal owing to temperature changes.

Question 9

The equilibrium constant for the formation of hydrogen iodide from hydrogen and iodine-H₂(g) + I₂(s) ⇄ 2 HI(g)-is 45.0 at a certain temperature.Which statement(s) regarding this equilibrium is/are true? I.The reaction is product favored.
II.The reaction is reactant favored.
III.Equilibrium lies to the right.
IV.Equilibrium lies to the left.

A)I and III
B)I and IV
C)II and III
D)II and IV
E)None are true, as the concentrations of reactants and products are essentially the same.

Question 10

Which statement below concerning a chemical reaction at equilibrium is true?

A)Only the forward reaction stops.
B)Only the reverse reaction stops.
C)Both the forward and reverse reactions stop.
D)The rate constants for the forward and reverse reactions are equal.
E)The rates of the forward and reverse reactions are equal.

Question 11

Which statement below regarding the equilibrium constant and its units is true?

A)K is unitless because the concentrations or partial pressures in the expression are theoretically ratios of concentration or partial pressure to an ideal value of 1.000 M or 1.000 atm.
B)K is unitless because the units of the concentrations or partial pressures in the expression are dropped for convenience.
C)K is unitless because the units of the concentrations or partial pressures in the expression cancel if the equilibrium expression is written correctly.
D)K has units that reflect the units of the concentrations or partial pressures in the equilibrium expression.
E)K has units of M or atm, depending on whether solutions or gases are involved.

Question 12

For an equilibrium reaction with K = 1.2 * 10⁸, the forward rate constant was found to be 3.5*10⁵.What is the value of the reverse rate constant?

A)3.5 *10⁵
B)3.4*10²
C)4.2 * 10¹³
D)6.0 * 10^-
E)2.9 * 10^-3

Question 13

Consider the equilibrium that exists between Fe²⁺ and Fe³⁺ ions in solution.The extra electron originally on one Fe²⁺ ion can be transferred to an Fe³⁺ ion.This amounts to no net reaction because iron(II) becomes iron(III) and iron(III) becomes iron(II).Which below about this equilibrium is true?

A)There is no activation energy for this reaction.
B)K = 1.
C)K =0.
D)There is no net reaction, so there is no value for K.
E)The concentrations of iron(II) and iron(III) change because of the electron transfer.

Question 14

Which of the following is/are equal once equilibrium is established?

A)the concentrations of reactant and products
B)the rates of the forward and reverse reactions
C)the time that a particular atom or molecule spends as a reactant and product
D)the rate constants of the forward and reverse reactions
E)All of the above are equal.

Question 15

Which statement below regarding the concentration of products for a chemical reaction at equilibrium is true?

A)They will not change because there are no more reactants.
B)They will not change because the limiting reagent is gone.
C)They will not change because this is a constant for each reaction.
D)They will not change because the forward and reverse rates are equal.
E)They will change continually because of reversibility.

Question 16

A chemical equilibrium A ⇄ 2 B has a forward rate constant, k_f =20.0 s^-1, and a reverse rate constant, k_r = 0.400 M ^-1 s^-1.What is the value of the equilibrium constant for this system?

A)8.00
B)50.0
C)125
D)0.0200
E)25.0

Question 17

A chemical equilibrium A ⇄ 2 B has a forward rate constant, k_f = 20.0 s^-1, and a reverse rate constant, k_r =0.400 M ^-1 s^-1.If the system has a concentration of [A] = 0.10 M at equilibrium, what is the concentration of B at equilibrium?

A)0.0447
B)5.00
C)0.0224
D)2.24
E)22.4

Question 18

Which statement below regarding reaction rates and equilibrium is FALSE?

A)For a reaction to attain equilibrium, reactants and products must remain in contact with each other.
B)The rate of the forward reaction is at its maximum when the reactants are first mixed.
C)The rate of the reverse reaction is at its maximum when the reactants are first mixed.
D)The rate of the forward reaction decreases as the system approaches equilibrium.
E)The rate of the reverse reaction increases as the system approaches equilibrium.

Question 19

Consider the equilibrium 2 NOCl(g) ⇄ NO(g) + CL₂ (g).At 800.0 K, the equilibrium constant is approximately 6.1 * 10^-8.Which statement below about this equilibrium is true?

A)There is no activation energy for this reaction.
B)There is no net reaction, so there is no value for K.
C)K = 1.
D)k_f is less than k_r at equilibrium.
E)The forward reaction rate is less than the reverse reaction rate.

Question 20

For the equilibrium CO₂ (g) +N₂ (g) ⇄ CO(g) +N₂O(g), the forward and reverse rate constants at 1200 K are 9.1 *10^-11 M ^-1 s^-1 and 1.5 *10⁵ M ^-1 s^-1, respectively.What is the value of the equilibrium constant for CO(g) + N₂O(g) ⇄ CO₂ (g) +N₂ (g)?

A)1.6 *10¹⁵
B)1.4 *10^-5
C)6.1 *10^-16
D)7.1 * 10⁴
E)1.0

Question 21

The equilibrium constants for the two reactions are known:
M ^m++ 4 L^- ⇄ [ML4]^m-4 $\quad$ K_f
HL ⇄ H⁺ +L^- $\quad$ K_a
What is the equilibrium constant, K_overall, for the reaction, M ^m++ 4 HL ⇄ [ML4 ]^{m + 4} +4H⁺?

A)K_fK_a
B)K_f+ 4K_a
C)K_f + K_a4
D)K_fK_a4
E)K_fK_a1/4

Question 22

For the chemical equilibrium aA + bB ⇄ cC, the value of the equilibrium constant K is 10.What is the value of the equilibrium constant for the reaction cC ⇄ aA + bB?

A)0.1
B)10
C)1
D)100
E)(-10)

Question 23

Consider the following equilibrium: CO(g) +3 H₂ (g) ⇄ CH₄ (g) +H₂O(g).If K_p = 1.61 *10^-5 at 1400.0 K, calculate K_c.

A)1.40 * 10^-7
B)1.85 * 10^-3
C)541
D)0.212
E)1.22 * 10^-9

Question 24

Consider the following equilibrium: CH₄ (g) +2 H₂ S(g) ⇆ CS₂ (g) +4 H₂ (g).If K_p= 33.0 at 1400.0 K, calculate K_c.

A)3.79 * 10³
B)2.50 *10^-3
C)0.287
D)4.36 *10⁵
E)3.48

Question 25

The following reactions at 1000.0 K have the following K_p values: H₂ (g) + CL₂ (g) ⇄ 2 HCl(g) K_p = 3.8 * 10⁴
H₂ (g) + Br₂ (g) ⇄ 2 HBr(g)) K_p =5.1 *10⁸
Br₂ (g) + CL₂ (g) ⇄ 2 Br Cl(g) K_p = 0.20
What is K_p for the reaction HCl(g) + HBr(g) ⇄ BrCl(g) + H₂(g) at 1000.0 K?

A)5.1 *10^-7
B)1.0 *10^-7
C)5.2*10^-15
D)0.45
E)1.0 *10^-14

Question 26

Under what conditions are the values of K_c and K_p for a given gas-phase equilibrium the same?

A)There is no change in the moles of gas in the reaction.
B)There is no change in the temperature during the reaction.
C)The coefficients of the reactants and products are the same.
D)The pressure remains constant.
E)Either K_c or K_p = 1.

Question 27

Consider the equilibrium 2 NOClg)  CL₂ g) + 2 NOg).When 2.000 atm NOCl is placed in an empty tank at 500.0 K and allowed to come to equilibrium, the equilibrium partial pressure of Cl₂ is 0.226 atm.Calculate K_p.

A)0.0115
B)15.2
C)0.0193
D)0.0660
E)52.0

Question 28

Consider the following equilibrium: ClF₃ (g) ⇄ ClF(g) + F₂ (g).When 0.500 atm ClF₃ is placed in a reaction vessel at 700.0 K, its equilibrium partial pressure is 0.296 atm.Calculate K_c at 700.0 K.

A)408
B)0.123
C)0.429
D)0.141
E)2.45 *10^-3

Question 29

For the equilibrium CH₄ (g) +2 H₂ S(g) ⇆ CS₂ (g) +4 H₂ (g), the concentrations at equilibrium are [CH₄] = 0.3322 M, [H₂S] = 0.6644 M, [CS₂] =0.0678 M, and [H₂] =0.2712 M at 1400.0 K.Calculate K_c.

A)0.167
B)2.50 * 10^-3
C)4.00 * 10²
D)6.00
E)0.694

Question 30

Consider the following equilibrium: CH₄ (g) +H₂O(g) ⇄ CO(g) +3 H₂ (g).When 1.00 M CH₄ and 1.00 M H₂O are placed in a reaction vessel at 1400.0 K, their equilibrium concentrations are 0.530 M.Calculate K_p at 1400 K.

A)4.69
B)3.55 * 10^-4
C)6.19 * 10⁴
D)539
E)0.0408

Question 31

The equilibrium constant for the formation of calcium carbonate from the ions in solution is 2.2 *10⁸ according to the reaction Ca²⁺(aq) + CO₃^{2 -} (aq) ⇄ CaCO₃ (s).What is the value of the equilibrium
Constant for the reverse of this reaction?

A)the same, 2.2 *10⁸
B)(-2.2 *10⁸)
C)2.2 *10^-8
D)4.5 * 10^-9
E)4.5 *10⁹

Question 32

For the chemical equilibrium aA + bB ⇄ cC, the value of the equilibrium constant K is 10.What is the value of the equilibrium constant for the reaction 2cC ⇄ 2aA + 2bB?

A)0.1
B)0.2
C)0.01
D)20
E)10

Question 33

Consider the equilibrium CL₂ (g) + 2 NO(g) ⇄ 2 NOCl(g).When 2.000 M NOCl is placed in an empty tank at 500.0 K and allowed to come to equilibrium, the equilibrium concentration of Cl₂ is 0.979 M.Calculate K_c.

A)45.6
B)15.2
C)0.938
D)2130
E)4.70 * 10^-4

Question 34

Which statement below regarding the mass action expression and the equilibrium constant expression is FALSE?

A)The mass action expression is usually applied to systems that have not attained equilibrium.
B)The mass action expression and the equilibrium constant expression have the same mathematical form.
C)The mass action expression never has the same value as the equilibrium constant expression.
D)There are infinitely many values for the mass action expression at a given temperature.
E)There is only one value of the equilibrium constant expression at a given temperature.

Question 35

For the chemical equilibrium aA + bB ⇄ cC, the value of the equilibrium constant K is 10.What is the value of the equilibrium constant for the reaction 2aA+2bB ⇄ 2cC?

A)10
B)20
C)40
D)100
E)400

Question 36

The law of mass action is a result of

A)the law of conservation of matter.
B)the law of conservation of energy.
C)kinetics of reversible reactions.
D)limiting reagent stoichiometry.
E)the third law of thermodynamics.

Question 37

Two students measure the equilibrium constant for the same chemical reaction.One student finds K_c to be 130; the other calculates K_c to be 11.4.The instructor checks their results and says they are both correct.Which statement below is a plausible explanation?

A)The values vary according to the way the measurement is made.One student must have measured product concentrations whereas the second must have measured reactant concentrations.
B)The values vary according to the starting conditions of the reaction prior to equilibrium.One student must have started with all reactants whereas the second must have started with all products.
C)The values vary according to the stoichiometric coefficients that are used.The balancing coefficients that the first student used must have been twice those that the second used.
D)The values vary according to direction of the reaction.One student must have used the reverse reaction.
E)The instructor must have made a mistake, as the equilibrium constant for a reaction must always be the same.

Question 38

At room temperature an increase in the number of moles of gas as the reaction goes from reactants to products in a gas-phase equilibrium results in

A)K_p $\gt$ K_c.
B)K_p $\lt$ K_c.
C)K_p = K_c.
D)K_p + K_c =(RT) ^{$\Delta$ n}.
E)K_pK_c=(RT) ^{$\Delta$ n}.

Question 39

For the equilibrium 2 PH₃ (g) ⇄ P ₂ (g) +3 H₂ (g), the equilibrium partial pressures are PPH= 0.022 atm, PP = 0.289 atm, and PH = 0.867 atm at 873 K.Calculate K_p.

A)0.0585
B)17.1
C)0.0441
D)2.50* 10^-3
E)389

Question 40

For the following hypothetical equilibrium, A +2 B ⇄ C, what is the value of the equilibrium constant if the concentrations at equilibrium are [A] = 4.5 *10^-5 M, [B] = 2.2 *10^-2 M, and [C] = 9.4 *10^-3 M?

A)0.22
B)9.9
C)4.3 * 10⁵
D)2.3 *10⁸
E)9.5*10³

Question 41

In equilibrium expressions, the concentrations of pure solids and liquids

A)have the assigned value of one.
B)have the assigned value of zero.
C)have constant values, c_s and c₁.
D)are determined from the density and molar mass.
E)are treated as any other solute.

Question 42

Consider the equilibrium CH₄ (g) + H₂ O(g) +206 kJ ⇄ CO(g) +3 H₂ (g).Which of the following disturbances will NOT cause the system to shift to the right to reestablish equilibrium?

A)The partial pressure of CH₄ increases.
B)The partial pressure of CO decreases.
C)The volume decreases.
D)The temperature increases.
E)All of these will cause the system to shift to the right.

Question 43

In a simple equilibrium A(g) +B(g) ⇄ C(g), will there be any stress to the system if both B and C are added to the equilibrium system simultaneously and in the same amount?

A)No, these two stresses will always cancel each other out.
B)No, these two stresses will cancel each other out unless the initial concentrations of B and C are also the same.
C)Yes, the same amount of A is also required for the stresses to cancel.
D)Yes, unless the initial concentrations of B and C are also the same.
E)More than two of the above statements are correct.

Question 44

Consider the equilibrium A +B ⇄ C.What is significant about the reaction quotient when [B] = [C]?

A)only that [B] = [C]
B)[A] = [B]= [C]
C)[B] = [C] = K
D)[A]=K
E)The reaction must run in the forward direction.

Question 45

For the equilibrium N₂ (g) +O₂ (g) ⇄ 2 NO(g), K_p = 0.0017 at 2300 K.At a given point, the partial pressures of the gases are P_{N 2} =P_O2 = 0.660 atm and P_NO = 0.0272 atm.Which statement below is true?

A)Q $\lt$ K, so the reaction will continue to make more products.
B)Q $\gt$ K, so the reaction will consume products to make more reactants.
C)Q = K, so the system is at equilibrium.
D)The value of K will decrease until it is equal to Q.
E)The value of K will increase until it is equal to Q.

Question 46

Which statement below, if any, is NOT a perturbation or stress to the equilibrium position of an endothermic chemical reaction that involves one or more gases?

A)adding reactants to a gas or solution reaction
B)removing products from a gas or solution reaction
C)decreasing the temperature
D)increasing pressure by adding an inert gas to a reaction in the gas phase
E)All of the above are perturbations to chemical equilibrium.

Question 47

If the reaction quotient Q has a larger value than the related equilibrium constant K,

A)the reaction is at equilibrium.
B)the reaction will continue to make more products.
C)the reaction will consume products and make reactants.
D)the reaction will release heat to achieve equilibrium.
E)the value of K will increase until it is equal to Q.

Question 48

For the equilibrium H₂ (g) + S(s) ⇄ H₂ S(g), K_c =6.1*10⁵ at 298 K.If the concentrations of H₂ and H₂S are equal, which statement below is true?

A)The concentration of S equals K_c.
B)The equilibrium constant equals 1.
C)The reaction quotient equals 1.
D)The system is at equilibrium.
E)The concentrations of H₂ and H₂S can never be equal.

Question 49

For the equilibrium 2 NO(g) +3H₂O₂ (g) ⇄ 2 NH₃ (g) + 4O₂ (g), K_p = 0.244 at 1400 K.At a given point, the partial pressures of the gases are PNO =0.0382 atm, PH₂ O₂ = 0.0974 atm, PNH ₃ = 0.264 atm, and PO₂ = 0.126 atm.Which statement below is true?

A)Q $\lt$ K, so the reaction will continue to make more products.
B)Q $\gt$ K, so the reaction will consume products to make more reactants.
C)Q= K, so the system is at equilibrium.
D)The value of K will decrease until it is equal to Q.
E)The value of K will increase until it is equal to Q.

Question 50

Which of the following occurs when products are removed from a chemical reaction in solution or the gas phase at equilibrium?

A)Q increases and the equilibrium shifts to produce more products.
B)Q increases and the equilibrium shifts to produce more reactants.
C)Q decreases and the equilibrium shifts to produce more products.
D)Q decreases and the equilibrium shifts to produce more reactants.
E)Q is unchanged by the addition of reactants.

Question 51

Which statement below regarding the effect of a catalyst on chemical equilibrium is true?

A)Only the forward rate increases, so the quantity of products increases.
B)Only the forward rate increases, but the quantity of products remains the same.
C)Both the forward and reverse rates increase and the quantity of products increases.
D)Both the forward and reverse rates increase, but the quantity of products is unchanged.
E)The effect varies depending on whether the reaction is endothermic or exothermic.

Question 52

An equilibrium that strongly favors products has

A)a value of K $\ll$ 1.
B)a value of K $\gg$ 1.
C)a value of Q $\gg$ 1.
D)a value of Q $\ll$ 1.
E)K = Q.

Question 53

For a chemical reaction at equilibrium, which actions) below will change the value of the equilibrium constant K? I.Changing the temperature
II)Changing the total concentration of reactants and products
III)Changing the reaction coefficients

A)I only
B)II only
C)III only
D)I and II only
E)I and III only

Question 54

Increasing the temperature of an exothermic reaction results in

A)more products and fewer reactants.
B)more reactants and fewer products.
C)more reactants and products.
D)fewer reactants and products.
E)no change in the quantities of reactants and products.

Question 55

Which of the following occurs when reactants are added to a chemical reaction in solution or the gas phase at equilibrium?

A)Q increases and the equilibrium shifts to produce more products.
B)Q increases and the equilibrium shifts to produce more reactants.
C)Q decreases and the equilibrium shifts to produce more products.
D)Q decreases and the equilibrium shifts to produce more reactants.
E)Q is unchanged by the addition of reactants.

Question 56

For the equilibrium 2 NOBr(g) ⇄ 2 NO(g) + Br₂ (g), K_c = 1.56 * 10^-3 at 300 K.Suppose 0.400 M NOBr is placed in a reaction vessel at 300 K.At a given point, the concentration of Br₂ is 0.0134 M.Which statement below is true?

A)Q $\lt$ K, so the reaction will continue to make more products.
B)Q $\gt$ K, so the reaction will consume products to make more reactants.
C)Q = K, so the system is at equilibrium.
D)The value of K will decrease until it is equal to Q.
E)The value of K will increase until it is equal to Q.

Question 57

If the reaction quotient Q has a smaller value than the related equilibrium constant K,

A)the reaction is at equilibrium.
B)the reaction will continue to make more products.
C)the reaction will consume products and make reactants.
D)the reaction will release heat to achieve equilibrium.
E)the value of K will decrease until it is equal to Q.

Question 58

Cylinders of NO gas may contain small quantities of oxygen as impurities, leading to the formation of NO₂ in equilibrium with the NO and oxygen.Is this contamination by NO₂ dependent on pressure in the tank?

A)Yes, there will be more NO₂ at higher pressures.
B)Yes, there will be less NO₂ at higher pressures.
C)No, the amount of NO₂ has nothing to do with pressure.
D)No, the amount of NO₂ depends on the partial pressure, not the total pressure.
E)There is no way to tell without additional information.

Question 59

Addition of reactants to a chemical reaction in solution or gas phase at equilibrium results in

A)an increase in K and a shift in equilibrium to produce more products.
B)an increase in K and a shift in equilibrium to produce more reactants.
C)a decrease in K and a shift in equilibrium to produce more products.
D)a decrease in K and a shift in equilibrium to produce more reactants.
E)no change in K and a shift in equilibrium to produce more products.

Question 60

If the temperature of an endothermic reaction at equilibrium could be increased instantaneously, what would be the instantaneous effect on Q and K before equilibrium was again achieved?

A)Q would increase and K would stay the same.
B)Q would decrease and K would stay the same.
C)Q would stay the same and K would increase.
D)Q would stay the same and K would decrease.
E)Both Q and K would stay the same.

Question 61

What happens to the equilibrium between NO₂g) and N₂O₄g) in inert argon when the volume is increased and additional argon is added to maintain a constant total pressure?

A)The ratio of NO₂ to N₂O₄ increases solely because of the increase in volume.
B)The ratio of NO₂ to N₂O₄ increases solely because of the addition of argon.
C)The ratio of NO₂ to N₂O₄ decreases solely because of the increase in volume.
D)The ratio of NO₂ to N₂O₄ decreases solely because of the addition of argon.
E)The ratio of NO₂ to N₂O₄ remains the same, as the effects of the two processes cancel.

Question 62

Which of the following relationships are sufficient to ensure that reactants and products will be in their standard state at equilibrium?
I. $\Delta$ G = 0
II. $\Delta$ G $\degree$ = 0
III.K = 1

A)I only
B)II only
C)III only
D)II and III only
E)Reactants and products can never be in equilibrium in their standard states.

Question 63

For the reaction 2 H₂ S(g) ⇆ 2 H₂ (g) + S₂ (g), K_c =1.7 * 10^-7 at 800.0 $\degree$
C.If the initial concentration of H₂S in a closed container is 0.75 M, what is the approximate equilibrium concentration of H₂?

A)0.37 M
B)3.2 * 10^-3 M
C)6.3 * 10^-3 M
D)5.8 * 10^-3 M
E)2.9 * 10^-3 M

Question 64

The decomposition of NOCl to form NO and Cl₂, 2 NOCl(g) ⇄ 2 NO(g) + CL₂ (g), has a K_p value of 1.6 *10^-5 at some temperature.If the initial partial pressures of NO and Cl₂ in a closed container are 0.80 atm and 0.40 atm, respectively, what is the approximate equilibrium partial pressure of NOCl?

A)0.77 atm
B)0.79 atm
C)0.80 atm
D)0.014 atm
E)0.027 atm

Question 65

When can an x be ignored in solving an equilibrium expression derived from a RICE table?

A)whenever it simplifies the calculation
B)whenever it is very much smaller than the term it is added to or subtracted from
C)whenever the equilibrium concentration for that species is relatively very small
D)whenever it is raised to any power higher than 1
E)never

Question 66

The decomposition of NOCl to form NO and Cl₂, 2 NOCl(g) ⇄ 2 NO(g) + CL₂ (g), has a K_p value of 1.6 *10^-5 at some temperature.If 0.500 atm of NOCl is placed in a closed vessel and allowed to come to equilibrium, what is its approximate equilibrium partial pressure?

A)0.013 atm
B)0.025 atm
C)0.48 atm
D)0.49 atm
E)0.50 atm

Question 67

The reaction of hydrogen gas with chlorine gas, H₂ g) + CL₂ g)  2 HClg), has a K_p value of 0.500.If 0.250 atm of both H₂ and Cl₂ are placed in a closed vessel and allowed to come to equilibrium, what is the equilibrium partial pressure of HClg)?

A)0.250 atm
B)0.104 atm
C)0.0653 atm
D)0.177 atm
E)0.131 atm

Question 68

Which of the following must be true for a reaction to proceed to form products?

A)Q $\gt$ K, $\Delta$ G $\lt$ 0, and $\Delta$ G $\degree$ $\lt$ 0
B)Q $\lt$ K and $\Delta$ G $\lt$ 0; $\Delta$ G $\degree$ can be anything
C)Q $\gt$ K and $\Delta$ G $\degree$ $\lt$ 0; $\Delta$ G can be anything
D)Q $\lt$ K, $\Delta$ G $\lt$ 0, and $\Delta$ G $\degree$ $\lt$ 0
E)Q $\lt$ K and $\Delta$ G $\degree$ $\lt$ 0; $\Delta$ G can be anything

Question 69

The fluoride ion, F-, reacts with water as a weak base: F^-(aq) + H₂ O(l) ⇄ HF(aq) + OH^-(aq), with K = 1.5 * 10^-11 at 25 $\degree$
C.If sodium fluoride were dissolved in water to make a 0.150 M solution, what would be the resulting concentration of OH^-?

A)0.15 M
B)1.5 * 10^-6 M
C)1.1 * 10^-12 M
D)5.8* 10^-7 M
E)2.3 * 10^-12 M

Question 70

If K for a reaction is large,

A)( $\Delta$ G $\degree$ is definitely negative.)
B)( $\Delta$ G $\degree$ is definitely positive.)
C)( $\Delta$ G $\degree$ is equal to zero.)
D)( $\Delta$ G is definitely negative.)
E)( $\Delta$ G is definitely positive.)

Question 71

Which of the choices below contains quantities that may have only positive values?

A)K and Q
B)( $\Delta$ G, $\Delta$ H, and $\Delta$ S)
C)ln K and ln Q
D)K and $\Delta$ G $\degree$
E)none of the above

Question 72

The reaction of bromine gas with chlorine gas, Br₂ (g) + CL₂ (g) ⇄ 2 BrCl(g), has a K_p value of 7.20.If the initial partial pressures of Br₂, Cl₂, and BrCl in a closed container are all 0.500 atm, what is the equilibrium partial pressure of BrCl(g)?

A)0.500 atm
B)0.680 atm
C)0.029 atm
D)0.859 atm
E)0.987 atm

Question 73

For a particular hypothetical reaction, 2A(aq) +B(aq) $\rightarrow$ C(aq), the value of $\Delta$ G $\degree$ is 2.50 * 10² kJ/mol.What is the value of $\Delta$ G for this reaction at 298 K when [A] = 0.600 M, [B]= 0.100 M, and [C]= 4.00 *10^-3 M ?

A)2.48 * 10² kJ/mol
B)2.45 * 10² kJ/mol
C)2.78* 10³ kJ/mol
D)2.50 *10² kJ/mol
E)2.55* 10² kJ/mol

Question 74

A reaction X + 2Y ⇄ 3 Z is started with 1.0 M Z and no X or Y.To calculate the equilibrium concentrations of all species using a RICE table, which of the following would you enter in the Z column for the C row?

A)1.0 M
B)1.0 M - x
C)1.0 M - 3x
D)1.0 M + 3x
E)(-3x)

Question 75

A sketch of the free energy for a hypothetical chemical equilibrium is shown here.What part of the plot on the axis representing the relative quantities of reactants and products corresponds to a value of $\Delta$ G that is greater than zero?

A)a to c
B)c only
C)c to d
D)b to d
E)none of these

Question 76

For the gas-phase oxidation of sulfur dioxide, 2 SO₂ (g) +O₂ (g) ⇄ 2 SO₃ (g), K_p = 4.17 * 10² at 200.0 $\degree$
C.If a closed vessel is filled with SO₃ at an initial pressure of 0.033 atm at 200 $\degree$
C, what is the equilibrium partial pressure of SO₃?

A)more than 0.033 atm
B)less than 0.033 atm
C)0.033 atm exactly
D)equal to 0.033/4.17 * 10²
E)More information is required.

Question 77

A perturbation or stress to a chemical reaction at equilibrium

A)increases the free energy of the system.
B)decreases the free energy of the system.
C)neither increases nor decreases the free energy of the system.
D)may increase or decrease the free energy of the system depending on the nature of the stress.
E)causes the free energy of the system to become zero.

Question 78

For the reaction 2 H₂ S(g) ⇆ 2 H₂ (g) + S₂ (g), K_p =1.5 * 10^-5 at 800.0 $\degree$
C.If the initial partial pressures of H₂ and S₂ in a closed container are 4.00 atm and 2.00 atm, respectively, what is the approximate equilibrium partial pressure of H₂S?

A)0.0783 atm
B)0.0493 atm
C)0.0247 atm
D)3.95 atm
E)3.92 atm

Question 79

In the equation relating equilibrium to thermodynamics, a - =RTb,

A)a = $\Delta$ G and b = ln K.
B)a = $\Delta$ G and b = K.
C)a = $\Delta$ G= and b =ln K.
D)a = $\Delta$ G= and b = K.
E)a = ln $\Delta$ G= and b = K.

Question 80

What is the value of the equilibrium constant at 462 K for a chemical equilibrium that has a $\Delta$ H $\degree$ value of=46.0 kJ/mol and a $\Delta$ S $\degree$ value of =92.0 J/mol · K?

A)1.0 * 10¹⁰
B)1.6 * 10^-5
C)0.40
D)2.5
E)6.3 * 10⁴