Question 1

At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.

Accepted Answer

A) True 
 B)False

Question 2

At 25°C, the equilibrium constant, Kc, 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?

Accepted Answer

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

Question 3

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?

Accepted Answer

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. 
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 4

What is used to explain the effect of a stress that has been applied to a system at equilibrium?

Accepted Answer

Le Châteli

Question 5

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?

Accepted Answer

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

Question 6

The solubility product constant, Ksp, 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)

Accepted Answer

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 
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 7

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?

Accepted Answer

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

Question 8

At 340. K, KP = 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?

Accepted Answer

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

Question 9

When the reaction 2H2S(g)   2H2(g) + S2(g) is carried out at 1065°C, KP = 0.012. Starting with pure H2S at 1065°C, what must the initial pressure of H2S be if the equilibrated mixture at this temperature is to contain 0.250 atm of H2(g)?

Accepted Answer

A)  1.06 atm 
B)  1.86 atm 
C)  0.94 atm 
D)  0.90 atm 
E)  1.52 atm 
A)  1.06 atm 
B)  1.86 atm 
C)  0.94 atm 
D)  0.90 atm 
E)  1.52 atm

Question 10

At 850°C, the equilibrium constant, KP, 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?

Accepted Answer

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

Question 11

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

Accepted Answer

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

Question 12

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

Accepted Answer

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

Question 13

Which of the following is the expression that relates Kc to KP?

Accepted Answer

A)  Kc = KPR/T 
B)  KP = Kc(RT)Δn 
C)  KP = Kc/(RT)Δn 
D)  KcKP = RT/V 
E)  KP = KcP/RT 
A)  Kc = KPR/T 
B)  KP = Kc(RT)Δn 
C)  KP = Kc/(RT)Δn 
D)  KcKP = RT/V 
E)  KP = KcP/RT

Question 14

Suppose 50.0 g of N2O4 is introduced into an evacuated 2.00-L vessel and allowed to come to equilibrium with its decomposition product, N2O4(g)   2NO2(g). For this reaction Kc = 0.133. Once the system has reached equilibrium, 5.00 g of NO2 is injected into the vessel, and the system is allowed to equilibrate once again. What is the mass of NO2 in the final equilibrium mixture?

Accepted Answer

A)  7.8 g 
B)  12.4 g 
C)  14.7 g 
D)  19.7 g 
E)  15.5 g 
A)  7.8 g 
B)  12.4 g 
C)  14.7 g 
D)  19.7 g 
E)  15.5 g

Question 15

For the endothermic reaction A2(g)   2A(g), a snapshot of an equilibrium mixture of A(g) and A2(g) may look as follows. (Each circle represents 1.0 mol of A atoms, and the volume of the box is 1.0 L.)   What is the equilibrium constant KP for this reaction at 298 K? (R = 0.08206 L • atm/K • mol)

Accepted Answer

A)  1.3 ×102 
B)  65 
C)  0.22 
D)  16 
E)  5.33 
A)  1.3 ×102 
B)  65 
C)  0.22 
D)  16 
E)  5.33

Question 16

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 Kc for the above reaction?

Accepted Answer

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

Question 17

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?

Accepted Answer

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. 
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 18

The equilibrium constant for the reaction AgBr(s)   Ag+(aq) + Br- (aq) is the solubility product constant, Ksp = 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)

Accepted Answer

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 
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 19

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?

Accepted Answer

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. 
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 20

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

Accepted Answer

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

Exam 15: Chemical Equilibrium

At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.

At 25°C, the equilibrium constant, Kc, 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?

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?

What is used to explain the effect of a stress that has been applied to a system at equilibrium?

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?

The solubility product constant, Ksp, 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)

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?

At 340. K, KP = 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?

When the reaction 2H2S(g) 2H2(g) + S2(g) is carried out at 1065°C, KP = 0.012. Starting with pure H2S at 1065°C, what must the initial pressure of H2S be if the equilibrated mixture at this temperature is to contain 0.250 atm of H2(g)?

At 850°C, the equilibrium constant, KP, 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?

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

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

Which of the following is the expression that relates Kc to KP?

For the endothermic reaction A2(g) 2A(g), a snapshot of an equilibrium mixture of A(g) and A2(g) may look as follows. (Each circle represents 1.0 mol of A atoms, and the volume of the box is 1.0 L.) What is the equilibrium constant KP for this reaction at 298 K? (R = 0.08206 L • atm/K • mol)

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?

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?

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

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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?

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 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?

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)

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?

When the reaction 2H₂S(g) 2H₂(g) + S₂(g) is carried out at 1065°C, K_P = 0.012. Starting with pure H₂S at 1065°C, what must the initial pressure of H₂S be if the equilibrated mixture at this temperature is to contain 0.250 atm of H₂(g)?

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?

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

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)

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

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?

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?

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)