Question 1

For some gas-phase reactions, Kp = Kc.

Accepted Answer

A) True 
 B)False

Question 2

N2(g) + O2(g) ⇄ 2NO(g) Kc = 4.8 × 10−31 2NOBr(g) ⇄ 2NO(g) + Br2(g) Kc = 0.50
Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction
2NOBr(g) ⇄ N2(g) + O2(g) + Br2(g)?

Accepted Answer

A) 2.4 × 10 −31 
B) 9.6 × 10 −31 
C) 1.0 × 10 30 
D) 4.2 × 10 30 
E) None of these choices are correct. 
A) 2.4 × 10 −31 
B) 9.6 × 10 −31 
C) 1.0 × 10 30 
D) 4.2 × 10 30 
E) None of these choices are correct.

Question 3

Once a reaction system reaches equilibrium, the concentrations of reactions and products no longer change.

Accepted Answer

A) True 
 B)False

Question 4

The following reaction is at equilibrium at a pressure of 1 atm, in a closed container. NaOH(s) + CO2(g) ⇄ NaHCO3(s) ΔH°rxn 2 gas present at equilibrium?

Accepted Answer

A) Adding N 2 gas to double the pressure 
B) Adding more solid NaOH 
C) Increasing the volume of the container 
D) Lowering the temperature 
E) None of these choices are correct. 
A) Adding N 2 gas to double the pressure 
B) Adding more solid NaOH 
C) Increasing the volume of the container 
D) Lowering the temperature 
E) None of these choices are correct.

Question 5

The reaction quotient for a gas phase reaction has a value of 2000. If the number of moles of reactants in the reaction equation is equal to that of the products, which of the following statements is definitely TRUE?

Accepted Answer

A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) When the system is at equilibrium, the concentrations of the products will be much larger than the concentrations of the reactants. 
D) The concentrations of the products are generally larger than the concentrations of the reactants. 
E) None of these choices are correct. 
A) The reaction must proceed to the left to establish equilibrium. 
B) The reaction must proceed to the right to establish equilibrium. 
C) When the system is at equilibrium, the concentrations of the products will be much larger than the concentrations of the reactants. 
D) The concentrations of the products are generally larger than the concentrations of the reactants. 
E) None of these choices are correct.

Question 6

When a chemical system is at equilibrium,

Accepted Answer

A) the concentrations of the reactants are equal to the concentrations of the products. 
B) the concentrations of the reactants and products have reached constant values. 
C) the forward and reverse reactions have stopped. 
D) the reaction quotient, Q, has reached a maximum. 
E) the reaction quotient, Q, has reached a minimum. 
A) the concentrations of the reactants are equal to the concentrations of the products. 
B) the concentrations of the reactants and products have reached constant values. 
C) the forward and reverse reactions have stopped. 
D) the reaction quotient, Q, has reached a maximum. 
E) the reaction quotient, Q, has reached a minimum.

Question 7

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

Question 8

Magnesium hydroxide is used in several antacid formulations. When it is added to water it dissociates into magnesium and hydroxide ions. Mg(OH)2(s) ⇄ Mg2+(aq) + 2OH−(aq)
The equilibrium constant at 25°C is 8.9 × 10−12. One hundred grams of magnesium hydroxide is added to 1.00 L of water and equilibrium is established. What happens to the solution if another 10 grams of Mg(OH)2 are now added to the mixture?

Accepted Answer

A) The hydroxide ion concentration will decrease. 
B) The hydroxide ion concentration will increase. 
C) The hydroxide ion concentration will be unchanged. 
D) The solution will become supersaturated. 
E) None of these choices are correct. 
A) The hydroxide ion concentration will decrease. 
B) The hydroxide ion concentration will increase. 
C) The hydroxide ion concentration will be unchanged. 
D) The solution will become supersaturated. 
E) None of these choices are correct.

Question 9

Hydrogen sulfide can be formed in the following reaction: H2(g) + ½S2(g) ⇄ H2S(g) ΔH°rxn = −92 kJ
The equilibrium constant Kp = 106 at 1023 K. Estimate the value of Kp at 1218 K.

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

Question 10

About half of the sodium carbonate produced is used in making glass products because it lowers the melting point of sand, the major component of glass. When sodium carbonate is added to water it hydrolyses according to the following reactions. CO32−(aq) + H2O(l) ⇄ HCO3−(aq) + OH−(aq) K1
HCO3(aq) + H2O(l) ⇄ H2CO3(aq) + OH−(aq) K2
These can be combined to yield
CO32−(aq) + 2H2O(l) ⇄ H2CO3(aq) + 2OH−(aq) K3
What is the value of K3?

Accepted Answer

A) K 1 × K 2 
B) K 1 ÷ K 2 
C) K 1 + K 2 
D) K 1 − K 2 
E) ( K 1 K 2)2 
A) K 1 × K 2 
B) K 1 ÷ K 2 
C) K 1 + K 2 
D) K 1 − K 2 
E) ( K 1 K 2)2

Question 11

Methanol can be synthesized by combining carbon monoxide and hydrogen. CO(g) + 2H2(g) ⇄ CH3OH(g) ΔH°rxn = −90.7 kJ
A reaction vessel contains these compounds at equilibrium. What effect will be seen when equilibrium is re-established after decreasing the temperature by 45°C?

Accepted Answer

A) All the partial pressures will decrease. 
B) The partial pressure of methanol will decrease. 
C) The partial pressures of hydrogen and methanol will decrease. 
D) The partial pressure of hydrogen will increase. 
E) The partial pressure of carbon monoxide will decrease. 
A) All the partial pressures will decrease. 
B) The partial pressure of methanol will decrease. 
C) The partial pressures of hydrogen and methanol will decrease. 
D) The partial pressure of hydrogen will increase. 
E) The partial pressure of carbon monoxide will decrease.

Question 12

H2SO3(aq) ⇄ HSO3(aq) + H+(aq) Kc = 1.4 × 10−2 H2SO3(aq) ⇄ SO32−(aq) + 2H+(aq) Kc = 9.1 × 10−10
Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction
HSO3−(aq) ⇄ SO32−(aq) + H+(aq)?

Accepted Answer

A) 6.5 ×10 −8 
B) 1.3 × 10 −11 
C) 7.8 × 10 10 
D) 1.5 × 10 7 
E) None of these choices are correct. 
A) 6.5 ×10 −8 
B) 1.3 × 10 −11 
C) 7.8 × 10 10 
D) 1.5 × 10 7 
E) None of these choices are correct.

Question 13

At 500°C the equilibrium constant, Kp, is 4.00 × 10−4 for the equilibrium: 2HCN(g) ⇄ H2(g) + C2N2(g)
What is Kp for the following reaction?
H2(g) + C2N2(g) ⇄ 2HCN(g)

Accepted Answer

A) 2.00 × 10 −4 
B) −4.00 × 10 −4 
C) 1.25 × 10 3 
D) 2.50 × 10 3 
E) 4.00 × 10 4 
A) 2.00 × 10 −4 
B) −4.00 × 10 −4 
C) 1.25 × 10 3 
D) 2.50 × 10 3 
E) 4.00 × 10 4

Question 14

Although a system may be at equilibrium, the rate constants of the forward and reverse reactions will in general be different.

Accepted Answer

A) True 
 B)False

Question 15

Nitric oxide and bromine were allowed to react in a sealed container. When equilibrium was reached PNO = 0.526 atm,   = 1.59 atm, and PNOBr = 7.68 atm. Calculate Kp for the reaction.
2NO(g) + Br2(g) ⇄ 2NOBr(g)

Accepted Answer

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

Question 16

Consider the reactions of cadmium with the thiosulfate anion. Cd2+(aq) + S2O32−(aq) ⇄ Cd(S2O3)(aq) K1 = 8.3 × 103
Cd(S2O3)(aq) + S2O32−(aq) ⇄ Cd(S2O3)22−(aq) K2 = 2.5 × 102
What is the value for the equilibrium constant for the following reaction?
Cd2+(aq) + 2S2O32−(aq) ⇄ Cd(S2O3)22−(aq)

Accepted Answer

A) 0.030 
B) 33 
C) 8.1 × 10 3 
D) 8.6 × 10 3 
E) 2.1 × 10 6 
A) 0.030 
B) 33 
C) 8.1 × 10 3 
D) 8.6 × 10 3 
E) 2.1 × 10 6

Question 17

The equilibrium constant Kc 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?

Accepted Answer

A) 0.049 M 
B) 0.11 M 
C) 0.30 M 
D) 0.59 M 
E) 0.83 M 
A) 0.049 M 
B) 0.11 M 
C) 0.30 M 
D) 0.59 M 
E) 0.83 M

Question 18

If all the reactants and products in an equilibrium reaction are in the gas phase, then Kp = Kc.

Accepted Answer

A) True 
 B)False

Question 19

Chemical reactions generally reach equilibrium because one of the reactants is used up.

Accepted Answer

A) True 
 B)False

Question 20

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 Kc for this reaction?

Accepted Answer

A) 0.309 
B) 0.601 
C) 1.66 
D) 3.24 
E) > 10 
A) 0.309 
B) 0.601 
C) 1.66 
D) 3.24 
E) > 10

Exam 17: Equilibrium: the Extent of Chemical Reactions

For some gas-phase reactions, Kp = Kc.

N2(g) + O2(g) ⇄ 2NO(g) Kc = 4.8 × 10−31 2NOBr(g) ⇄ 2NO(g) + Br2(g) Kc = 0.50 Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction 2NOBr(g) ⇄ N2(g) + O2(g) + Br2(g)?

Once a reaction system reaches equilibrium, the concentrations of reactions and products no longer change.

The following reaction is at equilibrium at a pressure of 1 atm, in a closed container. NaOH(s) + CO2(g) ⇄ NaHCO3(s) ΔH°rxn < 0 Which, if any, of the following actions will decrease the concentration of CO2 gas present at equilibrium?

The reaction quotient for a gas phase reaction has a value of 2000. If the number of moles of reactants in the reaction equation is equal to that of the products, which of the following statements is definitely TRUE?

When a chemical system is at equilibrium,

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?

Hydrogen sulfide can be formed in the following reaction: H2(g) + ½S2(g) ⇄ H2S(g) ΔH°rxn = −92 kJ The equilibrium constant Kp = 106 at 1023 K. Estimate the value of Kp at 1218 K.

Methanol can be synthesized by combining carbon monoxide and hydrogen. CO(g) + 2H2(g) ⇄ CH3OH(g) ΔH°rxn = −90.7 kJ A reaction vessel contains these compounds at equilibrium. What effect will be seen when equilibrium is re-established after decreasing the temperature by 45°C?

H2SO3(aq) ⇄ HSO3(aq) + H+(aq) Kc = 1.4 × 10−2 H2SO3(aq) ⇄ SO32−(aq) + 2H+(aq) Kc = 9.1 × 10−10 Given the above equilibrium constant data at 25°C, what is the value of Kc at this temperature for the reaction HSO3−(aq) ⇄ SO32−(aq) + H+(aq)?

At 500°C the equilibrium constant, Kp, is 4.00 × 10−4 for the equilibrium: 2HCN(g) ⇄ H2(g) + C2N2(g) What is Kp for the following reaction? H2(g) + C2N2(g) ⇄ 2HCN(g)

Although a system may be at equilibrium, the rate constants of the forward and reverse reactions will in general be different.

Nitric oxide and bromine were allowed to react in a sealed container. When equilibrium was reached PNO = 0.526 atm, = 1.59 atm, and PNOBr = 7.68 atm. Calculate Kp for the reaction. 2NO(g) + Br2(g) ⇄ 2NOBr(g)

The equilibrium constant Kc 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?

If all the reactants and products in an equilibrium reaction are in the gas phase, then Kp = Kc.

Chemical reactions generally reach equilibrium because one of the reactants is used up.

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 Kc for this reaction?

Keys to the Study of Chemistry: Definitions, Units, and Problem Solving

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids, Solids, and Phase Changes

The Properties of Mixtures: Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics: Entropy, Free Energy, and Reaction Direction

Electrochemistry: Chemical Change and Electrical Work

The Elements in Nature and Industry

Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

For some gas-phase reactions, K_p = K_c.

N₂(g) + O₂(g) ⇄ 2NO(g) K_c = 4.8 × 10⁻³¹ 2NOBr(g) ⇄ 2NO(g) + Br₂(g) K_c = 0.50 Given the above equilibrium constant data at 25°C, what is the value of K_c at this temperature for the reaction 2NOBr(g) ⇄ N₂(g) + O₂(g) + Br₂(g)?

The following reaction is at equilibrium at a pressure of 1 atm, in a closed container. NaOH(s) + CO₂(g) ⇄ NaHCO₃(s) ΔH°_rxn < 0 Which, if any, of the following actions will decrease the concentration of CO₂ gas present at equilibrium?

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?

Hydrogen sulfide can be formed in the following reaction: H₂(g) + ½S₂(g) ⇄ H₂S(g) ΔH°_rxn = −92 kJ The equilibrium constant K_p = 106 at 1023 K. Estimate the value of K_p at 1218 K.

Methanol can be synthesized by combining carbon monoxide and hydrogen. CO(g) + 2H₂(g) ⇄ CH₃OH(g) ΔH°_rxn = −90.7 kJ A reaction vessel contains these compounds at equilibrium. What effect will be seen when equilibrium is re-established after decreasing the temperature by 45°C?

H₂SO₃(aq) ⇄ HSO₃(aq) + H⁺(aq) K_c = 1.4 × 10⁻² H₂SO₃(aq) ⇄ SO₃²⁻(aq) + 2H⁺(aq) K_c = 9.1 × 10⁻¹⁰ Given the above equilibrium constant data at 25°C, what is the value of K_c at this temperature for the reaction HSO₃⁻(aq) ⇄ SO₃²⁻(aq) + H⁺(aq)?

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) + C₂N₂(g) ⇄ 2HCN(g)

Nitric oxide and bromine were allowed to react in a sealed container. When equilibrium was reached P_NO = 0.526 atm, = 1.59 atm, and P_NOBr = 7.68 atm. Calculate K_p for the reaction. 2NO(g) + Br₂(g) ⇄ 2NOBr(g)

The equilibrium constant K_c for the reaction PCl₃(g) + Cl₂(g) ⇄ PCl₅(g) Is 49 at 230°C. If 0.70 mol of PCl₃is added to 0.70 mol of Cl₂in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl₃when equilibrium has been established?

If all the reactants and products in an equilibrium reaction are in the gas phase, then K_p = K_c.

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?