Equilibrium and LeChatelier's Principle Quiz

Name:

Multiple Choice
Identify the choice that best completes the statement or answers the question.

The value of K_eq for the equilibrium

H₂ (g) + I₂ (g)

2 HI (g)

is 794 at 25°C. What is the value of K_eq for the equilibrium below?

1/2 H₂ (g) + 1/2 I₂ (g)

HI (g)

a.	397
b.	0.035
c.	28
d.	1588
e.	0.0013

The value of K_eq for the equilibrium

H₂ (g) + I₂ (g)

2 HI (g)

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

HI (g)

1/2 H₂ (g) + 1/2 I₂ (g)

a.	1588
b.	28
c.	397
d.	0.035
e.	0.0013

At elevated temperatures, molecular hydrogen and molecular bromine react to partially form hydrogen bromide:

H₂ (g) + Br₂(g)

2HBr (g)

A mixture of 0.682 mol of H₂ and 0.440 mol of Br₂ is combined in a reaction vessel with a volume of 2.00 L. At equilibrium at 700 K, there are 0.566 mol of H₂ present. At equilibrium, there are __________ mol of Br₂ present in the reaction vessel.

a.	0.000
b.	0.440
c.	0.566
d.	0.232
e.	0.324

Dinitrogentetraoxide partially decomposes according to the following equilibrium:

N₂O₄ (g)

2NO₂ (g)

A 1.00-L flask is charged with0.0400 mol of N₂O₄. At equilibrium at 373 K, 0.0055 mol of N₂O₄ remains. K_eq for this reaction is __________.

a.	2.2 ´ 10^-4
b.	13
c.	0.22
d.	0.022
e.	0.87

In the coal-gasification process, carbon monoxide is converted to carbon dioxide via the following reaction:

CO (g) + H₂O (g)

CO₂ (g) + H₂ (g)

In an experiment, 0.35 mol of CO and 0.40 mol of H₂O were placed in a 1.00-L reaction vessel. At equilibrium, there were 0.19 mol of CO remaining. K_eq at the temperature of the experiment is __________.

a.	5.47
b.	0.75
c.	1.78
d.	0.56
e.	1.0

The equilibrium constant (K_p) for the interconversion of PCl₅ and PCl₃ is 0.0121:

PCl₅ (g)

PCl₃ (g) + Cl₂ (g)

A vessel is charged with PCl₅, giving an initial pressure of 0.123 atm. At equilibrium, the partial pressure of PCl₃ is __________ atm.

a.	0.0782
b.	0.0455
c.	0.0908
d.	0.0330
e.	0.123

At equilibrium, __________.

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

Which one of the following is true concerning the Haber process?

a.	It is a process used for shifting equilibrium positions to the right for more economical chemical synthesis of a variety of substances.
b.	It is a process used for the synthesis of ammonia.
c.	It is another way of stating LeChatelier's principle.
d.	It is an industrial synthesis of sodium chloride that was discovered by Karl Haber.
e.	It is a process for the synthesis of elemental chlorine.

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

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

10.

Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide?

N₂O₄ (g)

2NO₂ (g)

a.
b.
c.
d.	[NO₂][N₂O₄]
e.	[NO₂]²[N₂O₄]

11.

Given the following reaction at equilibrium, if K_c = 6.44 x 10⁵at 230.0°C, K_p = __________.

2NO (g) + O₂ (g)

2NO₂ (g)

a.	3.67 x 10^-2
b.	1.56 x 10⁴
c.	6.44 x 10⁵
d.	2.66 x 10⁶
e.	2.67 x 10⁷

12.

Given the following reaction at equilibrium at 450.0°C:

CaCO₃ (s)

CaO (s) + CO₂ (g)

If pCO₂ = 0.0160 atm, K_c = __________.

a.	0.0160
b.	0.0821
c.	7.23
d.	2.70 x 10^-4
e.	723

13.

Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

(NH₄)₂Se (s)

2NH₃ (g) + H₂Se (g)

a.	[NH₃][H₂Se] / [(NH₄)₂Se]
b.	[(NH₄)₂Se] / [NH₃]²[H₂Se]
c.	1 / [(NH₄)₂Se]
d.	[NH₃]²[H₂Se]
e.	[NH₃]²[H₂Se] / [(NH₄)₂Se]

14.

Which of the following expressions is the correct equilibrium-constant expression for the reaction below?

HF (aq) + H₂O (l)

H₃O⁺ (aq) + F^- (aq)

a.	[HF][H₂O] / {H₃O⁺][F^-]
b.	1 / [HF]
c.	[H₃O⁺][F^-] / [HF][H₂O]
d.	[H₃O⁺][F^-] / [HF]
e.	[F^-] / [HF]

15.

The equilibrium constant for the gas phase reaction

N₂ (g) + 3H₂ (g)

2NH₃ (g)

is K_eq = 4.34 ´ 10^-3 at 300°C. At equilibrium, __________.

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

16.

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)

a.	K²
b.	2K
c.	1/2K
d.	1/K²
e.	-K²

17.

The equilibrium expression for K_p for the reaction below is __________.

2O₃(g) 3O₂(g)

a.
b.
c.
d.
e.

18.

The K_eq for the equilibrium below is 0.112 at 700.0°C.

SO₂ (g) +

O₂ (g)

SO₃ (g)
What is the value of K_eq at this temperature for the following reaction?

SO₃ (g)

SO₂ (g) +

O₂ (g)

a.	0.224
b.	0.0125
c.	0.112
d.	8.93
e.	-0.112

19.

The expression for K_p for the reaction below is __________.

4CuO (s) + CH₄ (g)

CO₂ (g) + 4Cu (s) + 2H₂O (g)

a.
b.
c.
d.
e.

20.

At 400 K, the equilibrium constant for the reaction

Br₂ (g) + Cl₂ (g)

2BrCl (g)

is K_p = 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.

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.

21.

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 0.46 mol of NOBr. How many moles of NO and Br₂, respectively, are in the flask at equilibrium?

a.	0.18, 0.18
b.	0.46, 0.23
c.	0.18, 0.090
d.	0.18, 0.360
e.	0.46, 0.46

22.

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

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)

23.

Consider the following reaction at equilibrium:

2NH₃ (g)

N₂ (g) + 3H₂ (g) DH° = +92.4 kJ

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

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)

24.

Consider the following reaction at equilibrium:

2CO₂ (g)

2CO (g) + O₂ (g) DH° = -514 kJ

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

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

25.

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?

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