Deck 15: Chemical Equilibrium

Question 1

Which substances are included in the equilibrium constant expression, K_c?

A) Only pure solids
B) Only pure liquids
C) Only pure solids and liquids
D) Only gases and dissolved substances
E) All participating substances

Answer 1

Only gases and dissolved substances

Question 2

For the following reaction at 25ºC, is 3 × 10²⁴. 2SO₂(g) + O₂(g) 2SO₃(g)
What is K_c at this temperature? (R = 0.08206 L • atm/K • mol)

A) 1 × 10²³
B) 1 × 10²⁴
C) 3 × 10²⁴
D) 6 × 10²⁴
E) 7 × 10²⁵

Answer 2

7 × 10²⁵

Question 3

Phosgene, COCl₂, a poisonous gas, decomposes as follows. COCl₂(g) CO(g) + Cl₂(g).
At 900.ºC, K_c = 0.083. What is K_P at this temperature? (R = 0.08206 L • atm/K • mol)

A) 0.125
B) 8.0
C) 6.1
D) 0.16
E) 0.083

Answer 3

8.0

Question 4

If, in a particular process, reactants are able to form products, and products are also able to form reactants, then this process may be described as

A) a reversible process.
B) an elementary process.
C) at equilibrium.
D) forbidden.
E) a forward process.

Question 5

What is the name for Q_c?

A) Reversibility expression
B) Reaction expression
C) Equilibrium expression
D) Reaction quotient
E) Mass action

Question 6

Hydrogen peroxide may decompose to form water and oxygen gas according to the following reaction. 2H₂O₂(g) 2H₂O(g) + O₂(g)
In a particular experiment, 1.75 moles of H₂O₂ were placed in a 2.5-L reaction chamber at 307ºC. After equilibrium was reached, 1.20 moles of H₂O₂ remained. What is K_c for the reaction?

A) 2.0 × 10^-4
B) 2.3 × 10^-2
C) 2.4 × 10^-3
D) 5.5 × 10^-3
E) 3.9 × 10^-4

Question 7

The observation that at equilibrium, the reaction quotient equals the equilibrium constant, is representative of which law?

A) Law of equal states
B) Reversibility law
C) Law of equivalence
D) Law of reactant-product equivalence
E) Law of mass action

Question 8

Which is the correct equilibrium constant expression for the following reaction? 2BrCl₃(g) Br₂(g) + 3Cl₂(g)

A) K_c = [Br₂] [Cl₂]/[BrCl₃]
B) K_c = [Br₂] [Cl₂]⁵/[BrCl₃]²
C) K_c = [Br₂] [Cl₂]³/[BrCl₃]²
D) K_c = [BrCl₃]²/([Br₂] × [Cl₂]³)
E) K_c = 2[BrCl₃]²/([Br₂] × 3[Cl₂]³)

Question 9

What is defined as a fraction with equilibrium product concentrations in the numerator and equilibrium reactant concentrations in the denominator and each concentration raised to a power equal to the corresponding stoichiometric coefficient in the balanced chemical equation?

A) Reversibility expression
B) Reaction expression
C) Equilibrium expression
D) Product quotient
E) Mass action

Question 10

The equilibrium constant for the reaction Ni(s) + 4CO(g) Ni(CO)₄(g) is 5.0 × 10⁴ at 25ºC. What is the equilibrium constant for the following reaction?
Ni(CO)₄(g) Ni(s) + 4CO(g)?

A) 2.0 × 10^-5
B) 2.5 × 10⁹
C) 5.0 × 10⁴
D) 5.0 × 10^-4
E) 2.0 × 10^-3

Question 11

A 6.0-L vessel was found to contain 1.0 mol BrCl₃, 2.0 mol Br₂ and 6.0 mol Cl₂ at equilibrium. What is the equilibrium constant, K_c, for this equilibrium mixture for the reaction
2BrCl₃(g) Br₂(g) + 3Cl₂(g)?

A) 0.014
B) 108
C) 18
D) 12
E) 432

Question 12

Which is the correct equilibrium constant expression for the following reaction? 2C₆H₆(g) + 15O₂(g) 12CO₂(g) + 6H₂O(g)

A)
B)
C)
D)
E)

Question 13

Which is the correct equilibrium constant expression for the following reaction? FeO(s) + H₂(g) Fe(s) + H₂O(g)

A) K_c = [H₂O]/[H₂]
B) K_c = [Fe] [H₂O]/[Fe₂O₃]
C) K_c = [Fe₂O₃] [H₂]/[Fe][H₂O]
D) K_c = [Fe][H₂O]/[Fe₂O₃] [H₂]
E) K_c = [H₂]/[H₂O]

Question 14

What is defined as a fraction with product concentrations in the numerator and reactant concentrations in the denominator and with each concentration raised to a power equal to the corresponding stoichiometric coefficient in the balanced chemical equation?

A) Reversibility expression
B) Reaction expression
C) Equilibrium expression
D) Reaction quotient
E) Mass action

Question 15

At elevated temperatures, hydrogen iodide may decompose to form hydrogen gas and iodine gas, as follows. 2HI(g) H₂(g) + I₂(g)
In a particular experiment, the concentrations at equilibrium were measured to be [HI] = 0.85 mol/L, [I₂] = 0.60 mol/L, and [H₂] = 0.27 mol/L. What is K_c for the above reaction?

A) 5.3
B) 0.22
C) 4.5
D) 0.19
E) 1.6 × 10²

Question 16

Carbon tetrachloride reacts at high temperatures with oxygen to produce two toxic gases, phosgene and chlorine. CCl₄(g) + ½O₂(g) COCl₂(g) + Cl₂(g), K_c = 4.4 × 10⁹ at 1000 K
What is K_c for the following reaction?
2CCl₄(g) + O₂(g) 2COCl₂(g) + 2Cl₂(g)

A) 6.6 × 10⁴
B) 4.4 × 10⁹
C) 8.8 × 10⁹
D) 1.9 × 10¹⁹
E) 2.3 × 10^-10

Question 17

During a chemical reaction, what defines when the concentrations of the reactants and products reach a constant level?

A) Elementary process
B) Reversible reaction
C) Rate law
D) Rate constant
E) Equilibrium

Question 18

Which statement is correct?

A) If Q < K, then products must be converted to reactants.
B) If Q > K, then reactants must be converted to products.
C) If Q = K, then the system is at equilibrium.
D) If Q < K, then more reactants are produced.
E) None of the answers is correct.

Question 19

Which is the correct mass-action expression, Q_c, for the following chemical reaction? Sn²⁺(aq) + ½ O₂(g) + 3H₂O(l) SnO₂(s) + 2H₃O⁺(aq)

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

Question 20

Consider the reversible reaction: 2NO₂(g) N₂O₄(g) If the concentrations of both NO₂ and N₂O₄ are each 0.016 M, what is the value of Q_c?

A) 0.016
B) 0.50
C) 1.0
D) 2.0
E) 63

Question 21

The equilibrium constant, K_P, for the reaction H₂(g) + I₂(g) 2HI(g) is 55.2 at 425°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?

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

Question 22

Nitrogen dioxide decomposes according to the reaction 2NO₂(g) 2NO(g) + O₂(g)
Where K_P = 4.48 × 10^-13 at 25°C. What is the value for K_c?(R = 0.08206 L • atm/K • mol)

A) 1.83 × 10^-14
B) 4.48 × 10^-14
C) 9.19 × 10^-13
D) 2.18 × 10^-13
E) 1.10 × 10^-11

Question 23

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 K_c for this reaction? CO(g) + Br₂(g) COBr₂(g)

A) 5.23
B) 2.14
C) 1.17
D) 0.467
E) 0.191

Question 24

Suppose 15.00 g of solid ammonium hydrogen sulfide is introduced into a 500.-mL flask at 25°C, the flask is sealed, and the system is allowed to reach equilibrium. What is the partial pressure of ammonia in this flask if K_P = 0.108 at 25°C for the following reaction? NH₄HS(s) NH₃(g) + H₂S(g)

A) 0.657 atm
B) 1.25 atm
C) 0.329 atm
D) 14.4 atm
E) 2.50 atm

Question 25

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

A) 0.209 M
B) 1.33 M
C) 0.267 M
D) 0.667 M
E) 0.600 M

Question 26

Consider the following equilibria: 2SO₃(g) 2SO₂(g) + O₂(g) K_c = 2.3 × 10^-7
2NO₃(g) 2NO₂(g) + O₂(g) K_c = 1.4 × 10^-3
Calculate the equilibrium constant for the reaction
SO₂(g) + NO₃(g) SO₃(g) + NO₂(g).

A) 78
B) 1.3 × 10^-2
C) 1.6 × 10^-4
D) 3.2 × 10^-10
E) 6.1 × 10³

Question 27

Consider the equilibrium reaction: N₂O₄(g) 2NO₂(g) Which of the following correctly describes the relationship between K_c and K_P for the reaction?

A) K_P = K_c
B) K_P = RT × K_c
C) K_P = (RT × K_c )^-1
D) K_P = K_c/RT
E) K_P = RT/K_c

Question 28

Nitric oxide is formed in automobile exhaust when nitrogen and oxygen in air react at high temperatures. N₂(g) + O₂(g) 2NO(g)
The equilibrium constant K_P for the reaction is 0.0025 at 2127°C. If a container is charged with 8.00 atm of nitrogen and 5.00 atm of oxygen and the mixture is allowed to reach equilibrium, what will be the equilibrium partial pressure of nitrogen?

A) 0.15 atm
B) 0.31 atm
C) 3.08 atm
D) 7.69 atm
E) 7.85 atm

Question 29

At 850°C, the equilibrium constant, K_P, for the reaction C(s) + CO₂(g) 2CO(g) has a value of 10.7.
If the total pressure in the system at equilibrium is 1.000 atm, what is the partial pressure of carbon monoxide at equilibrium?

A) 0.362 atm
B) 0.489 atm
C) 0.667 atm
D) 0.915 atm
E) 0.921 atm

Question 30

The equilibrium constant, K_P, has a value of 6.5 × 10^-4 at 308 K for the reaction of nitrogen monoxide with chlorine. 2NO(g) + Cl₂(g) 2NOCl(g)
What is the value of K_c? (R = 0.08206 L • atm/K • mol)

A) 2.5 × 10^-7
B) 6.5 × 10^-4
C) 1.6 × 10^-2
D) 1.7
E) None of these choices is correct.

Question 31

The reaction of nitrogen with oxygen to form nitrogen monoxide can be represented by the following equation. N₂(g) + O₂(g) 2NO(g)
At 2000.°C, the equilibrium constant, K_c, has a value of 4.10 × 10^-4. What is the value of K_P? (R = 0.08206 L • atm/K • mol)

A) 2.17 × 10^-8
B) 4.10 × 10^-4
C) 7.65 × 10^-2
D) 2.20 ×10^-6
E) 2.44 ×10³

Question 32

For the nitrogen fixation reaction, 3H₂(g) + N₂(g) 2NH₃(g), K_c = 6.0 × 10^-2 at 500°C. If 0.250 M H₂ and 0.050 M NH₃ are present at equilibrium, what is the equilibrium concentration of N₂?

A) 3.3 M
B) 2.7 M
C) 0.20 M
D) 0.083 M
E) 0.058 M

Question 33

At 500°C the equilibrium constant, K_P , is 4.00 × 10^-4 for the equilibrium: 2HCN(g) H₂(g) + C₂N₂(g)
What is K_p for the following reaction?
H₂(g) + C₂ N₂(g) 2HCN(g)

A) 2.00 × 10^-4
B) -4.00 × 10^-4
C) 1.25 × 10³
D) 2.50 × 10³
E) 4.00 × 10⁴

Question 34

Which of the following is the expression that relates K_c to K_P?

A) K_c = K_PR/T
B) K_P = K_c(RT)^Δn
C) K_P = K_c/(RT)^Δn
D) K_cK_P = RT/V
E) K_P = K_cP/RT

Question 35

Nitric oxide and bromine were allowed to react in a sealed container. When equilibrium was reached, the following partial pressures of three gases were measured: NO: 0.526 atm; Br₂ : 1.59 atm; NOBr: 7.68 atm. Calculate K_P for the reaction. 2NO(g) + Br₂(g) 2NOBr(g)

A) 7.45 × 10^-3
B) 0.109
C) 9.18
D) 91.8
E) 134

Question 36

Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide. NH₄I(s) NH₃(g) + HI(g)
At 400°C, K_P = 0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400°C.

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

Question 37

At 340. K, K_P = 69 for the reaction H₂(g) + I₂(g) 2HI(g). Suppose 50.0 g of HI is injected into an evacuated 5.00-L rigid cylinder at 340. K. What is the total pressure inside the cylinder when the system comes to equilibrium?

A) 2.60 atm
B) 1.76 atm
C) 0.424 atm
D) 2.18 atm
E) 0.171 atm

Question 38

At 25°C, the equilibrium constant, K_c, for the reaction 2A(g) B(g) + C(g) is 0.0350.
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?

A) 0.339 M
B) 0.378 M
C) 0.400 M
D) 0.677 M
E) 0.755 M

Question 39

The equilibrium constant, K_c, for the reaction PCl₃(g) + Cl₂(g) PCl₅(g) is 49 at 230°C.
If 0.70 mol of PCl₃ is added to 0.70 mol of Cl₂ in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl₃ when equilibrium has been established?

A) 0.049 M
B) 0.11 M
C) 0.35 M
D) 0.59 M
E) 0.83 M

Question 40

Compounds A, B, and C react according to the following equation. 3A(g) + 2B(g) 2C(g)
At 100°C a mixture of these gases at equilibrium showed that [A] = 0.855 M, [B] = 1.23 M, and [C] = 1.75 M. What is the value of K_c for this reaction?

A) 0.309
B) 0.601
C) 1.66
D) 2.25
E) 3.24

Question 41

Consider the reaction: 2A(g) + B(g) → 2C(g) If ΔG° = 50.0 kJ/mol at T = 25°C and P_A = P_B = 1 atm and P_C = 2 atm, what is the value of ΔG? (R = 8.314 J/K • mol)

A) 50.0 kJ/mol
B) 49.7 kJ/mol
C) 46.5 kJ/mol
D) 53.4 kJ/mol
E) -49.7 kJ/mol

Question 42

For the reaction HCONH₂(g) NH₃(g) + CO(g), K_c = 4.84 at 400 K. If ΔH° for this reaction is 29 kJ/mol, find K_c at 500 K.

A) 5.8
B) 0.17
C) 27.5
D) 0.88
E) 10.3

Question 43

The standard free energy of formation of gaseous hydrogen iodide is 1.30 kJ/mol at 25°C. What is K_P for the reaction H₂(g) + I₂(g) 2HI(g) at this temperature?

A) 0.35
B) 0.59
C) 1.0
D) 1.7
E) 2.9

Question 44

For the reaction H₂(g) + Br₂(g) 2HBr(g), K_c = 81.4 at 385ºC. If [H₂] = [Br₂] = [HBr] = 2.4 × 10^-4M at 385ºC, which one of the following is correct?

A) [H₂] and [HBr] decrease as the system moves toward equilibrium.
B) The system is at equilibrium.
C) [H₂] and [Br₂] increase as the system approaches equilibrium.
D) [HBr] increases as the system approaches equilibrium.
E) [HBr] and [Br₂] increases as the system approaches equilibrium.

Question 45

The equilibrium constant K_P at 427°C for the reaction N₂(g) + 3H₂(g) 2NH₃(g) is 9.4 × 10^-5. What is ΔG° for the reaction under these conditions? (R = 8.314 J/K • mol)

A) -33 kJ/mol
B) -54 kJ/mol
C) 54 kJ/mol
D) 33 kJ/mol
E) 1.3 J/mol

Question 46

A sample of solid naphthalene is introduced into an evacuated flask. Using the data below, what is the equilibrium vapor pressure of naphthalene (C₁₀H₈) in the flask at 35°C?

A) 890. mmHg
B) 0.22 mmHg
C) 696 mmHg
D) 0.086 mmHg
E) 833 mmHg

Question 47

In the gas phase, methyl isonitrile (CH₃NC) isomerizes to acetonitrile (CH₃CN), H₃C-N≡C(g) H₃C-C≡N(g)
With ΔH° = -89.5 kJ/mol and ΔG° = - 73.8 kJ/mol at 25°C. Find the equilibrium constant for this reaction at 100°C.

A) 1.68 × 10^-10
B) 5.96 × 10⁹
C) 2.16 × 10¹⁰
D) 4.63 × 10^-11
E) 8.64 × 10¹²

Question 48

What is K_P at 298 K for the following reaction? (R = 8.314 J/K • mol) SO₂(g) + NO₂(g) → SO₃(g) + NO(g)

A) 6.99 × 10^-7
B) 5.71 × 10^-8
C) 14.2
D) 475
E) 1.42 × 10⁶

Question 49

At 1500°C the equilibrium constant for the reaction CO(g) + 2H₂(g) CH₃OH(g) has the value K_P = 1.4 × 10^-7. What is ΔG° for this reaction at 1500°C? (R = 8.314 J/K • mol)

A) 105 kJ/mol
B) 1.07 kJ/mol
C) -233 kJ/mol
D) -105 kJ/mol
E) 233 kJ/mol

Question 50

Which is correct?

A) If ΔG < 0, then Q > K.
B) If ΔG < 0, then Q < K.
C) If ΔG < 0, then Q = K.
D) If ΔG^o < 0, then Q = K.
E) If ΔG^o < 0, then Q > K.

Question 51

Which represents the correct relationship between the Gibbs free energy and the equilibrium constant?

A) ΔG = -RT lnK
B) ΔG = RT lnK
C) ΔG^o = -RT lnK
D) ΔG^o = -RT lnQ
E) ΔG^o = RT lnQ

Question 52

Find the temperature at which K_P = 42.0 for the reaction H₂(g) + I₂(g) 2HI(g). [Given: at 25°C, for H₂(g), ΔH°_f = 0, S° = 131.0 J/mol • K; for I₂(g), ΔH°_f = 62.26 kJ/mol, S° = 260.6 J/mol • K; for HI(g), ΔH°_f = 25.9 kJ/mol, S° = 206.3 J/mol • K; assume that ΔH° and ΔS° are independent of temperature.]

A) 1040 K
B) 168 K
C) 539 K
D) 1400 K
E) 34,200 K

Question 53

At what temperature is K_P = 4.00 for the reaction N₂O₄(g) 2NO₂(g)? (R = 8.314 J/K • mol)

A) 197°C
B) 56°C
C) 36°C
D) 79°C
E) 476°C

Question 54

Nitrosyl chloride (NOCl) decomposes at elevated temperatures according to the equation 2NOCl(g) 2NO(g) + Cl₂(g). What is K_P for this reaction at 227°C?
For this reaction ΔH° = 81.2 kJ/mol and ΔS° = 128 J/K • mol. (R = 8.314 J/K • mol)

A) 1.60 × 10^-2
B) 2.10 × 10^-7
C) 62.8
D) 4.90 × 10⁶
E) 3.20 × 10⁹

Question 55

Hydrogen peroxide (H₂O₂) decomposes according to the following equation. H₂O₂(l) → H₂O(l) + ½O₂(g).
What is K_P for this reaction at 25°C? (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K • mol, R = 8.314 J/K • mol)

A) 1.3 × 10^-21
B) 20.9
C) 3.46 × 10¹⁷
D) 7.4 × 10²⁰
E) 8.6 × 10⁴

Question 56

For the reaction PCl₃(g) + Cl₂(g) PCl₅(g) at a particular temperature, K_c = 32.4. Suppose a system at that temperature is prepared with [PCl₅] = 0.50 M, [Cl₂] = 0.4 M, and [PCl₃] = 0.10 M. Which of the following is correct?

A) The system will proceed in the direction of forming more PCl₅ and Cl₂ until equilibrium is reached.
B) The system is at equilibrium.
C) The system will proceed in the direction of forming more PCl₅ until equilibrium is reached.
D) The system will proceed in the direction of forming more PCl₃ and Cl₂ until equilibrium is reached.
E) The system will proceed in the direction of forming more PCl₃ and PCl₅ until equilibrium is reached.

Question 57

The equilibrium constant for the reaction AgBr(s) Ag⁺(aq) + Br^- (aq) is the solubility product constant, K_sp = 7.7 × 10^-13 at 25°C. Calculate ΔG for the reaction when [Ag⁺] = 1.0 × 10^{-2 M} and [Br^-] = 1.0 × 10^{-3 M}. Is the reaction spontaneous or nonspontaneous at these concentrations? (R = 8.314 J/K • mol)

A) ΔG = 69.1 kJ/mol, nonspontaneous
B) ΔG = -69.1 kJ/mol, spontaneous
C) ΔG = 97.5 kJ/mol, spontaneous
D) ΔG = 40.6 kJ/mol, nonspontaneous
E) ΔG = -97.5 kJ/mol, nonspontaneous

Question 58

The solubility product constant, K_sp, at 25°C for AgI(s) in water has the value 8.3 × 10^-17. Calculate ΔG at 25°C for the process AgI(s) Ag⁺(aq) + I^-(aq) where [Ag⁺] = 9.1 × 10^{-9 M} and [I^-] = 9.1 × 10^{-9 M}. (R = 8.314 J/K • mol)

A) +4.4 kJ/mol
B) +91.7 kJ/mol
C) 0.0 kJ/mol
D) -91.7 kJ/mol
E) -4.4 kJ/mol

Question 59

In the gas phase, formic acid forms a dimer, 2HCOOH(g) (HCOOH)₂(g). For this reaction, ΔH° = -60.1 kJ/mol and ΔG° = -13.9 kJ/mol at 25°C. Find the equilibrium constant (K_P) for this reaction at 75 °C.

A) 8960
B) 273
C) 0.120
D) 8.33
E) 1.12 × 10^-4

Question 60

The reaction system POBr₃(g) POBr(g) + Br₂(g) is at equilibrium. Which of the following statements describes the behavior of the system if the partial pressure of bromine is reduced by 75% as equilibrium is established?

A) POBr will be consumed as equilibrium is established.
B) The partial pressure of POBr will decrease while the partial pressure of Br₂ increases as equilibrium is established.
C) POBr₃ will be consumed as equilibrium is established.
D) The volume will have to decrease before equilibrium can be reestablished.
E) Bromine will be generated as equilibrium is established.

Question 61

The reaction system POBr₃(g) POBr(g) + Br₂(g) is at equilibrium. Which of the following statements describes the behavior of the system if POBr is added to the container?

A) POBr will be consumed in order to establish a new equilibrium.
B) The partial pressures of POBr₃ and POBr will remain steady while the partial pressure of bromine increases.
C) The partial pressure of bromine will increase while the partial pressure of POBr decreases.
D) The partial pressure of bromine remains steady while the partial pressures of POBr₃ and POBr increase.
E) The forward reaction will proceed to establish equilibrium.

Question 62

Based on the following data, what is K_sp at 298 K of barium carbonate, BaCO₃? (R = 8.314 J/K • mol)

A) 5.86
B) 6.30 × 10⁸
C) 1.59 × 10^-9
D) 5.47 × 10^-21
E) 2.18 × 10^-27

Question 63

Which equation is correct?

A) ΔG = ΔG° - RT logK_eq
B) ΔG° = - RT lnK
C) ΔG = RT lnQ
D) ΔG = -RT logQ
E) ΔG° = -RT logK_eq

Question 64

Calculate K_P for the reaction 2NOCl(g) 2NO(g) + Cl₂(g) at 400.°C if K_c at 400.°C for this reaction is 2.1 × 10^-2. (R = 0.08206 L • atm/K • mol)

A) 6.4 × 10^-3
B) 1.7 × 10^-3
C) 0.69
D) 1.2
E) 3.8 × 10^-4

Question 65

Which statement is correct?

A) When Q < K then ΔG = 1.
B) When Q < K then ΔG = -ΔS.
C) When Q = K then ΔG = 0.
D) When Q > K then ΔG = 1.
E) When Q > K then ΔG = - RT.

Question 66

At 450°C, tert-butyl alcohol decomposes into water and isobutene. (CH₃)₃COH(g) (CH₃)₂CCH₂(g) + H₂O(g)
A reaction vessel contains these compounds at equilibrium. What will happen if the volume of the container is reduced by 50% at constant temperature?

A) The forward reaction will proceed in order to reestablish equilibrium.
B) The reverse reaction will proceed in order to reestablish equilibrium.
C) No change occurs.
D) The equilibrium constant will increase.
E) The equilibrium constant will decrease.

Question 67

Iron(III) oxide can be reduced by carbon monoxide. Fe₂O₃(s) + 3CO(g) 2Fe(s) + 3CO₂(g)
Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature. (R = 8.314 J/K • mol)

A) 7.0 × 10^-6
B) 1.3 × 10^-3
C) 2.2 × 10⁴
D) 1.4 × 10⁵
E) > 2.0 × 10⁵

Question 68

Hydrogen sulfide can be formed in the following reaction: H₂(g) + S₂(g) H₂S(g); ΔH°_rxn = -92 kJ/mol
The equilibrium constant,K_P,is 106 at 1023 K. Estimate the value of K_P at 1218 K. (R = 8.314 J/K • mol)

A) 5.05
B) 18.8
C) 34.7
D) 88.9
E) 598

Question 69

The following reactions occur at 500 K. Arrange them in order of increasing tendency to proceed to completion (least completion → greatest completion).

A) 2 < 1 < 3 < 4
B) 3 < 1 < 4 < 2
C) 3 < 4 < 1 < 2
D) 4 < 3 < 2 < 1
E) 4 < 3 < 1 < 2

Question 70

What is the free energy change, ΔG°, for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453°C? (R = 8.314 J/K• mol) 2HI(g) H₂(g) + I₂(g)K_c = 0.020 at T = 453°C

A) 6.4 kJ/mol
B) 8.8 kJ/mol
C) 15 kJ/mol
D) 19 kJ/mol
E) 24 kJ/mol

Question 71

When the following reaction is at equilibrium, which relationship is always true? 2NOCl(g) 2NO(g) + Cl₂(g)

A) [NO] [Cl₂] = [NOCl]
B) [NO]² [Cl₂] = [NOCl]²
C) [NOCl] = [NO]
D) 2[NO] = [Cl₂]
E) [NO]² [Cl₂] = K_c[NOCl]²

Question 72

If one starts with pure NO₂(g) at a pressure of 0.500 atm, the total pressure inside the reaction vessel when 2NO₂(g) 2NO(g) + O₂(g) reaches equilibrium is 0.674 atm. What is the equilibrium partial pressure of NO₂?

A) 0.152 atm
B) 0.174 atm
C) 0.200 atm
D) 0.326 atm
E) 0.500 atm

Question 73

Which statement is correct?

A) If K < 1, lnK is negative, and ΔG° is negative then, the reaction is product favored.
B) If K > 1, lnK is negative, and ΔG° is positive, then the reaction is product favored.
C) If K > 1, lnK is positive, and ΔG° is negative, then the reaction is product favored.
D) If K > 1, lnK is negative, and ΔG° is negative, then the reaction is reactant favored.
E) If K < 1, lnK is positive, and ΔG° is positive, then the reaction is reactant favored.

Question 74

Stearic acid, nature's most common fatty acid, dimerizes when dissolved in hexane: 2C₁₇H₃₅COOH (C₁₇H₃₅COOH)₂; ΔH°_rxn = -172 kJ/mol
The equilibrium constant for this reaction at 28°C is 2.9 × 10³. Estimate the equilibrium constant at 38°C. (R = 8.314 J/K• mol)

A) 4.7 × 10⁵
B) 2.6 × 10⁴
C) 1.9 × 10³
D) 3.2 × 10²
E) 18

Question 75

Which equation is correct?

A) ΔG = ΔG° - RT logK_eq
B) ΔG = ΔG° + RT lnQ
C) ΔG = RT lnQ
D) ΔG = -RT logQ
E) ΔG = -RT logK_eq

Question 76

For the reaction 2X(g) + Y(g) 2Z(g), K_c = 1.00 ×10³ at 500 K. If at equilibrium the concentration of X is 0.20 M and the concentration of Y is 0.50 M, what is the equilibrium concentration of Z?

A) 2.2 M
B) 3.2 M
C) 3.5 M
D) 4.5 M
E) 7.1 M

Question 77

The formation constant for the reaction Ag⁺(aq) + 2NH₃(aq) Ag(NH₃)₂⁺(aq)
Is K_f = 1.7 × 10⁷ at 25°C. What is ΔG° at this temperature? (R = 8.314 J/K• mol)

A) -1.5 kJ/mol
B) -3.5 kJ/mol
C) -18 kJ/mol
D) -23 kJ/mol
E) -41 kJ/mol

Question 78

The following reaction is at equilibrium in a sealed container. N₂(g) + 3H₂(g) 2NH₃(g); ΔH°_rxn < 0
Which, if any, of the following actions will increase the value of the equilibrium constant, K_c?

A) Adding more NH₃
B) Adding more N₂
C) Increasing the pressure
D) Lowering the temperature
E) Adding a catalyst

Question 79

Calculate the equilibrium constant at 25°C for the reaction of methane with water to form carbon dioxide and hydrogen. The data below are values at 25°C.(R = 8.314 J/K • mol) CH₄(g) + 2H₂O(g) CO₂(g) + 4H₂(g)

A) 8.2 × 10¹⁹
B) 0.96
C) 0.58
D) 1.2 × 10^-20
E) 1.4 × 10^-46

Question 80

A container was charged with hydrogen, nitrogen, and ammonia gases at 120°C and the system was allowed to reach equilibrium. What will happen if the volume of the container is increased at constant temperature? 3H₂(g) + N₂(g) 2NH₃(g)

A) There will be no effect.
B) More ammonia will be produced at the expense of hydrogen and nitrogen.
C) Hydrogen and nitrogen will be produced at the expense of ammonia.
D) The equilibrium constant will increase.
E) The equilibrium constant will decrease.