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Chapter 13- Chemical Equilibrium

Chapter 13- Chemical Equilibrium

Question 1 of 35

1

At equilibrium, __________.

Select one of the following:

  • A) all chemical reactions have ceased

  • B) the rates of the forward and reverse reactions are equal

  • C) the rate constants of the forward and reverse reactions are equal

  • D) the value of the equilibrium constant is 1

  • E) the limiting reagent has been consumed

Explanation

Question 2 of 35

1

Which one of the following will change the value of an equilibrium constant?

Select one of the following:

  • A) changing temperature

  • B) adding other substances that do not react with any of the species involved in the equilibrium

  • C) varying the initial concentrations of reactants

  • D) varying the initial concentrations of products

  • E) changing the volume of the reaction vessel

Explanation

Question 3 of 35

1

The equilibrium-constant expression depends on the __________ of the reaction.

Select one of the following:

  • A) stoichiometry

  • B) mechanism

  • C) stoichiometry and mechanism

  • D) the quantities of reactants and products initially present

  • E) temperature

Explanation

Question 4 of 35

1

The equilibrium constant for reaction 1 is K. The equilibrium constant for reaction 2 is __________.

(1) SO2 (g) + (1/2) O2 (g) --> SO3 (g)
(2) 2SO3 (g) --> 2SO2 (g) + O2 (g)

Select one of the following:

  • A) K2

  • B) 2K

  • C) 1/2K

  • D) 1/K2

  • E) -K2

Explanation

Question 5 of 35

1

The value of Keq for the following reaction is 0.25:

SO2 (g) + NO2 (g) ---> SO3 (g) + NO (g)

The value of Keq at the same temperature for the reaction below is __________.

2SO2 (g) + 2NO2 (g) ---> 2SO3 (g) + 2NO (g)

Select one of the following:

  • A) 0.50

  • B) 0.063

  • C) 0.12

  • D) 0.25

  • E) 16

Explanation

Question 6 of 35

1

The Keq for the equilibrium below is 7.52 × 10-2 at 480.0°C.

2Cl2 (g) + 2H2O (g) --> 4HCl (g) + O2 (g)

What is the value of Keq at this temperature for the following reaction?

4HCl (g) + O2 (g) --> 2Cl2 (g) + 2H2O (g)

Select one of the following:

  • A) 0.0752

  • B) -0.0752

  • C) 13.3

  • D) 5.66 × 10-3

  • E) 0.150

Explanation

Question 7 of 35

1

Given the following reaction at equilibrium, if Kc = 1.90 × 1019 at 25.0°C, Kp = __________.

H2 (g) + Br2 (g) ---> 2 HBr (g)

Select one of the following:

  • A) 5.26 × 10-20

  • B) 1.56 × 104

  • C) 6.44 × 105

  • D) 1.90 × 1019

  • E) none of the above

Explanation

Question 8 of 35

1

The equilibrium constant for the gas phase reaction

N2 (g) + 3H2 (g) --> 2NH3 (g)

is Keq = 4.34 × 10-3 at 300°C. At equilibrium, __________.

Select one of the following:

  • A) products predominate

  • B) reactants predominate

  • C) roughly equal amounts of products and reactants are present

  • D) only products are present

  • E) only reactants are present

Explanation

Question 9 of 35

1

The equilibrium constant for the gas phase reaction

2SO2 (g) + O2 (g) --> 2SO3 (g)

is Keq = 2.80 × 102 at 999 K. At equilibrium, __________.

Select one of the following:

  • A) products predominate

  • B) reactants predominate

  • C) roughly equal amounts of products and reactants are present

  • D) only products are present

  • E) only reactants are present

Explanation

Question 10 of 35

1

Consider the following equilibrium.

2SO2 (g) + O2 (g) --> 2SO3 (g)

The equilibrium cannot be established when __________ is/are placed in a 1.0-L container.

Select one of the following:

  • A) 0.25 mol SO2 (g) and 0.25 mol O2 (g)

  • B) 0.75 mol SO2 (g)

  • C) 0.25 mol of SO2 (g) and 0.25 mol of SO3 (g)

  • D) 0.50 mol O2 (g) and 0.50 mol SO3 (g)

  • E) 1.0 mol SO3 (g)

Explanation

Question 11 of 35

1

At 400 K, the equilibrium constant for the reaction

Br2 (g) + Cl2 (g) --> 2BrCl (g)

is Kp = 7.0. A closed vessel at 400 K is charged with 1.00 atm of Br2 (g), 1.00 atm of Cl2 (g), and 2.00 atm of BrCl (g). Use Q to determine which of the statements below is true.

Select one of the following:

  • A) The equilibrium partial pressures of Br2, Cl2, and BrCl will be the same as the initial values.

  • B) The equilibrium partial pressure of Br2 will be greater than 1.00 atm.

  • C) At equilibrium, the total pressure in the vessel will be less than the initial total pressure.

  • D) The equilibrium partial pressure of BrCl (g) will be greater than 2.00 atm.

  • E) The reaction will go to completion since there are equal amounts of Br2 and Cl2.

Explanation

Question 12 of 35

1

How is the reaction quotient used to determine whether a system is at equilibrium?

Select one of the following:

  • A) The reaction quotient must be satisfied for equilibrium to be achieved.

  • B) At equilibrium, the reaction quotient is undefined.

  • D) The reaction is at equilibrium when Q > Keq.

  • E) The reaction is at equilibrium when Q = Keq.

Explanation

Question 13 of 35

1

Of the following equilibria, only __________ will shift to the right in response to a decrease in volume.

Select one of the following:

  • A) H2 (g) + Cl2 (g) ---> 2 HCl (g)

  • B) 2 SO3 (g) ---> 2 SO2 (g) + O2 (g)

  • C) N2 (g) + 3 H2 (g) ---> 2 NH3 (g)

  • D) 2 Fe2O3 (s) ---> 4 Fe (s) + 3 O2 (g)

  • E) 2HI (g) ---> H2 (g) + I2 (g)

Explanation

Question 14 of 35

1

The reaction below is exothermic:

2SO2 (g) + O2 (g) ---> 2SO3 (g)

Le Châtelier's Principle predicts that __________ will result in an increase in the number of moles of SO3 (g) in the reaction container.

Select one of the following:

  • A) increasing the pressure

  • B) decreasing the pressure

  • C) increasing the temperature

  • D) removing some oxygen

  • E) increasing the volume of the container

Explanation

Question 15 of 35

1

For the endothermic reaction

CaCO3 (s) --> CaO (s) + CO2 (g)

Le Châtelier's principle predicts that __________ will result in an increase in the number of moles of CO2.

Select one of the following:

  • A) increasing the temperature

  • B) decreasing the temperature

  • C) increasing the pressure

  • D) removing some of the CaCO3 (s)

  • E) none of the above

Explanation

Question 16 of 35

1

In which of the following reactions would increasing pressure at constant temperature not change the concentrations of reactants and products, based on Le Châtelier's principle?

Select one of the following:

  • A) N2 (g) + 3H2 (g) 2NH3 (g)

  • B) N2O4 (g) 2NO2 (g)

  • C) N2 (g) + 2O2 (g) 2NO2 (g)

  • D) 2N2 (g) + O2 (g) 2N2O (g)

  • E) N2 (g) + O2 (g) 2NO (g)

Explanation

Question 17 of 35

1

Consider the following reaction at equilibrium:

2NH3 (g) ---> N2 (g) + 3H2 (g) ΔH° = +92.4 kJ

Le Châtelier's principle predicts that adding N2 (g) to the system at equilibrium will result in __________.

Select one of the following:

  • A) a decrease in the concentration of NH3 (g)

  • B) a decrease in the concentration of H2 (g)

  • C) an increase in the value of the equilibrium constant

  • D) a lower partial pressure of N2

  • E) removal of all of the H2 (g)

Explanation

Question 18 of 35

1

Consider the following reaction at equilibrium:

2NH3 (g) ----> N2 (g) + 3H2 (g)

Le Châtelier's principle predicts that the moles of H2 in the reaction container will increase with __________.

Select one of the following:

  • A) some removal of NH3 from the reaction vessel (V and T constant)

  • B) a decrease in the total pressure (T constant)

  • C) addition of some N2 to the reaction vessel (V and T constant)

  • D) a decrease in the total volume of the reaction vessel (T constant)

  • E) an increase in total pressure by the addition of helium gas (V and T constant)

Explanation

Question 19 of 35

1

Consider the following reaction at equilibrium:

2CO2 (g) ---> 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier's principle predicts that adding O2 (g) to the reaction container will __________.

Select one of the following:

  • A) increase the partial pressure of CO (g) at equilibrium

  • B) decrease the partial pressure of CO2 (g) at equilibrium

  • C) increase the value of the equilibrium constant

  • D) increase the partial pressure of CO2 (g) at equilibrium

  • E) decrease the value of the equilibrium constant

Explanation

Question 20 of 35

1

Consider the following reaction at equilibrium:

2CO2 (g) ----> 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier's principle predicts that an increase in temperature will __________.

Select one of the following:

  • A) increase the partial pressure of O2 (g)

  • B) decrease the partial pressure of CO2 (g)

  • C) decrease the value of the equilibrium constant

  • D) increase the value of the equilibrium constant

  • E) increase the partial pressure of CO

Explanation

Question 21 of 35

1

Consider the following reaction at equilibrium:

C (s) + H2O (g) ----> CO (g) + H2 (g)

Which of the following conditions will increase the partial pressure of CO?

Select one of the following:

  • A) decreasing the partial pressure of H2O (g)

  • B) removing H2O (g) from the system

  • C) decreasing the volume of the reaction vessel

  • D) decreasing the pressure in the reaction vessel

  • E) increasing the amount of carbon in the system

Explanation

Question 22 of 35

1

Consider the following reaction at equilibrium.

2CO2 (g) ---> 2CO (g) + O2 (g) ΔH° = -514 kJ

Le Châtelier's principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction __________.

Select one of the following:

  • A) at high temperature and high pressure

  • B) at high temperature and low pressure

  • C) at low temperature and low pressure

  • D) at low temperature and high pressure

  • E) in the presence of solid carbon

Explanation

Question 23 of 35

1

Consider the following reaction at equilibrium:

2SO2 (g) + O2 (g) --> 2SO3 (g) ΔH° = -99 kJ

Le Châtelier's principle predicts that an increase in temperature will result in __________.

Select one of the following:

  • A) a decrease in the partial pressure of SO3

  • B) a decrease in the partial pressure of SO2

  • C) an increase in Keq

  • D) no changes in equilibrium partial pressures

  • E) the partial pressure of O2 will decrease

Explanation

Question 24 of 35

1

The effect of a catalyst on an equilibrium is to __________.

Select one of the following:

  • A) increase the rate of the forward reaction only

  • B) increase the equilibrium constant so that products are favored

  • C) slow the reverse reaction only

  • D) increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture

  • E) shift the equilibrium to the right

Explanation

Question 25 of 35

1

The value of Keq for the equilibrium

H2 (g) + I2 (g) ---> 2 HI (g)

is 794 at 25 °C. What is the value of Keq for the equilibrium below?
1/2 H2 (g) + 1/2 I2 (g) ---> HI (g)

Select one of the following:

  • A) 397

  • B) 0.035

  • C) 28

  • D) 1588

  • E) 0.0013

Explanation

Question 26 of 35

1

The value of Keq for the equilibrium

H2 (g) + I2 (g) ---> 2 HI (g)

is 794 at 25°C. At this temperature, what is the value of Keq for the equilibrium below?

HI (g) ---> 1/2 H2 (g) + 1/2 I2 (g)

Select one of the following:

  • A) 1588

  • B) 28

  • C) 397

  • D) 0.035

  • E) 0.0013

Explanation

Question 27 of 35

1

Given the following reaction:

CO (g) + 2H2(g) ---> CH3OH (g)

In an experiment, 0.42 mol of CO and 0.42 mol of H2 were placed in a 1.00-L reaction vessel. At equilibrium, there were 0.29 mol of CO remaining. Keq at the temperature of the experiment is __________.

Select one of the following:

  • A) 2.80

  • B) 0.357

  • C) 14.5

  • D) 17.5

  • E) none of the above

Explanation

Question 28 of 35

1

At 200°C, the equilibrium constant (Kp) for the reaction below is 2.40 × 103.

2NO (g) ---> N2 (g) + O2 (g)

A closed vessel is charged with 36.1 atm of NO. At equilibrium, the partial pressure of O2 is __________ atm.

Select one of the following:

  • A) 294

  • B) 35.7

  • C) 17.9

  • D) 6.00

  • E) 1.50 × 10-2

Explanation

Question 29 of 35

1

Given the following reaction at equilibrium, if Kc = 6.34 x 105 at 230.0°C, Kp = __________.

2NO (g) + O2 (g) ---> 2NO2 (g)

Select one of the following:

  • A) 3.67 × 10-2

  • B) 1.53 × 104

  • C) 6.44 × 105

  • D) 2.61 × 106

  • E) 2.62 × 107

Explanation

Question 30 of 35

1

Nitrosyl bromide decomposes according to the following equation.

2NOBr (g) ---> 2NO (g) + Br2 (g)

A sample of NOBr (0.64 mol) was placed in a 1.00-L flask containing no NO or Br2. At equilibrium the flask contained 0.36 mol of NOBr. How many moles of NO and Br2, respectively, are in the flask at equilibrium?

Select one of the following:

  • A) .28,.28

  • B) .36,.18

  • C) .28,.14

  • D) .14,.23

  • E) .36,.36

Explanation

Question 31 of 35

1

If the value for the equilibrium constant is much greater than 1, then the equilibrium mixture contains mostly __________.

Select one of the following:

  • A) Reactants

  • B) Products

  • C) Neither, they are in equal amounts

Explanation

Question 32 of 35

1

The number obtained by substituting starting reactant and product concentrations into an equilibrium-constant expression is known as the __________.

Select one of the following:

  • A) Rate Constant

  • B) Reaction Quotient

  • C) Equilibrium Concentration

  • D) Reaction Rate

Explanation

Question 33 of 35

1

The relationship between the concentrations of reactants and products of a system at equilibrium is given by the law of mass action.

Select one of the following:

  • True

  • False

Explanation

Question 34 of 35

1

If a reaction is endothermic, __________ the reaction temperature results in an increase in K.

Select one of the following:

  • A) Increasing

  • B) Decreasing

  • C) Constant

Explanation

Question 35 of 35

1

For an exothermic reaction, increasing the reaction temperature results in a(an) __________ in K.

Select one of the following:

  • A) Increasing

  • B) Decreasing

  • C) Constant

Explanation

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