Which of the Following Statements Contains a Quotient

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Chemical Equilibrium Examples of Multiple Choice Questions

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1.

When the system A + B

C + D is at equilibrium,

(a) the sum of the concentrations of A and B must equal the sum of the concentrations of C and D.

(b) the forward reaction has stopped.

(c) both the forward and the reverse reactions have stopped.

(d) the reverse reaction has stopped.

(e) neither the forward nor the reverse reaction has stopped.

2.

2SO₃(g)

2SO₂(g) + O₂(g)
The conventional equilibrium constant expression (K_c) for the system as described by the above equation is:

(a) [SO₂]²/[SO₃]

(b) [SO₂]²[O₂]/[SO₃]²

(c) [SO₃]²/[SO₃]²[O₂]

(d) [SO₂][O₂]

(e) none of these

3.

Consider the following reversible reaction. In a 3.00 liter container, the following amounts are found in equilibrium at 400
^oC: 0.0420 mole N₂, 0.516 mole H₂
and 0.0357 mole NH₃. Evaluate K_c.
N₂(g) + 3H₂(g)

2NH₃(g)

(a) 0.202

(b) 1.99

(c) 16.0

(d) 4.94

(e) 0.503

4.

If the equilibrium constant for the reaction
A + 2B

C + 5/2 D
has a value of 4.0, what is the value of the equilibrium constant for the reaction
2C + 5D

2A + 4B
at the same temperature?

(a) 0.25

(b) 0.063

(c) 2.0

(d) 8.0

(e) 16

5.

At 445^oC, K_c
for the following reaction is 0.020.
2HI(g)

H₂(g) + I₂(g)
A mixture of H₂, I₂, and HI in a vessel at 445^oC has the following concentrations: [HI] = 2.0 M, [H₂] = 0.50 M and [I₂] = 0.10 M. Which one of the following statements concerning the reaction quotient, Q_c, is
TRUE
for the above system?

(a) Q_c
= K_c; the system is at equilibrium.

(b) Q_c
is less than K_c; more H₂
and I₂
will be produced.

(c) Q_c
is less than K_c; more HI will be produced.

(d) Q_c
is greater than K_c; more H₂
and I₂
will be produced.

(e) Q_c
is greater than K_c; more HI will be produced.

6.

Nitrosyl chloride, NOCl, dissociates on heating as shown below. When a 1.50 gram sample of pure NOCl is heated at 350^oC in a volume of 1.00 liter, the percent dissociation is found to be 57.2%. Calculate K_c
for the reaction as written.
NOCl(g)

NO(g) + 1/2 Cl₂(g)

(a) 0.876

(b) 9.26

(c) 0.107

(d) 1.75 x 10
^–4

(e) 0.0421

7.

A quantity of HI was sealed in a tube, heated to 425^oC and held at this temperature until equilibrium was reached. The concentration of HI in the tube at equilibrium was found to be 0.0706 mol/L. Calculate the equilibirum concentration of H₂
(and I₂). For the gas-phase reaction,

H2 + I2 2HI

Kc = 54.6 at 425oC

(a) 9.55 x 10
^–3
M

(b) 1.17 x 10
^–3
M

(c) 1.85 x 10
^–4
M

(d) 4.78 x 10
^–3
M

(e) 2.34 x 10
^–3
M

8.

Consider the reaction:

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

Kc = 0.10 at 2000oC

Starting with initial concentrations of 0.040 mol/L of N₂
and 0.040 mol/L of O₂, calculate the equilibrium concentration of NO in mol/L

(a) 0.0055 mol/L

(b) 0.0096 mol/L

(c) 0.011 mol/L

(d) 0.080 mol/L

(e) 0.10 mol/L

9.

K_c
= 0.040 for the system below at 450^oC. If a reaction is initiated with 0.40 mole of Cl₂
and 0.40 mole of PCl₃
in a 2.0 liter container, what is the equilibrium concentration of Cl₂
in the same system?
PCl₅(g)

PCl₃(g) + Cl₂(g)

(a) 0.07 M

(b) 0.16 M

(c) 0.11 M

(d) 0.04 M

(e) 0.26 M

10.

The reversible reaction:
2SO₂(g) + O₂(g)

2SO₃(g)
has come to equilibrium in a vessel of specific volume at a given temperature. Before the reaction began, the concentrations of the reactants were 0.060 mol/L of SO₂
and 0.050 mol/L of O₂. After equilibrium is reached, the concentration of SO₃
is 0.040 mol/L. What is the equilibrium concentration of O₂?

(a) 0.010 M

(b) 0.020 M

(c) 0.030 M

(d) 0.040 M

(e) none of these

11.

Consider the gas-phase equilibrium system represented by the equation:
2H₂O(g)

2H₂(g) + O₂(g)
Given that the forward reaction (the conversion of “left-hand” species to “right-hand” species) is
endothermic, which of the following changes will
decrease
the equilibrium amount of H₂O?

(a) adding more oxygen

(b) adding a solid phase calalyst

(c) decreasing the volume of the container (the total pressure increases)

(d) increasing the temperature at constant pressure

(e) adding He gas

12.

The conventional equilibrium constant expression (K_c) for the system below is:
2ICl(s)

I₂(s) + Cl₂(g)

(a) [I₂][Cl₂]/[ICl]²

(b) [I₂][Cl₂]/2[ICl]

(c) [Cl₂]

(d) ([I₂] + [Cl₂])/2[ICl]

(e) [Cl₂]/[ICl]²

13.

Consider the equilibrium system:
2ICl(s)

I₂(s) + Cl₂(g)
Which of the following changes will increase the total amount of of Cl₂
that can be produced?

(a) removing some of the I₂(s)

(b) adding more ICl(s)

(c) removing the Cl₂
as it is formed

(d) decreasing the volume of the container

(e) all of the above

14.

At equilibrium, a 1.0 liter container was found to contain 0.20 moles of A, 0.20 moles of B, 0.40 moles of C and 0.40 mole of D. If 0.10 moles of A and 0.10 moles of B are added to this system, what will be the new equilibrium concentration of A?
A(g) + B(g)

C(g) + D(g)

(a) 0.37 mol/L

(b) 0.47 mol/L

(c) 0.87 mol/L

(d) 0.23 mol/L

(e) 0.15 mol/L

15.

Consider the following system in a 1.00 L container:
A(g) + B(g)

2C(g)
The equilibrium concentrations at 200^oC were determined to be:

[A] = 0.200 M

[B] = 3.00 M

[C] = 0.500 M

How many moles of A must be added to increase the concentration of C to 0.700 M at 200^oC?

(a) 0.225 mol

(b) 0.305 mol

(c) 0.417 mol

(d) 0.610 mol

(e) 0.700 mol

16.

Consider the reversible reaction at equilibrium at 392^oC:
2A(g) + B(g)

C(g)
The partial pressures are found to be: A: 6.70 atm, B: 10.1 atm, C: 3.60 atm. Evaluate K_p
for this reaction.

(a) 7.94 x 10
^–3

(b) 0.146

(c) 0.0532

(d) 54.5

(e) 121

17.

K_c
= 0.040 for the system below at 450^oC:
PCl₅(g)

PCl₃(g) + Cl₂(g)
Evaluate K_p
for the reaction at 450^oC.

(a) 0.40

(b) 0.64

(c) 2.4

(d) 0.052

(e) 6.7 x 10
^–4

18.

What is the equilibrium constant for a reaction that has a value of
G^o
= -41.8 kJ at 100^oC?

(a) 1.01

(b) 7.1 x 10⁵

(c) -5.87

(d) 1.4 x 10
^–6

(e) 13.5

19.

The equilibrium constant at 427^oC for the reaction:
N₂(g) + 3H₂(g)

2NH₃(g)
is K_p
= 9.4 x 10
^–5. Calculate the value of
G^o
for the reaction at 427^o.

(a) -33 kJ

(b) -54 kJ

(c) 54 kJ

(d) 33 kJ

(e) 1.3 J

20.

For a specific reaction, which of the following statements can be made about K, the equilibrium constant?

(a) It always remains the same at different reaction conditions.

(b) It increases if the concentration of one of the products is increased.

(c) It changes with changes in the temperature.

(d) It increases if the concentration of one of the reactants is increased.

(e) It may be changed by the addition of a catalyst.

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Answers:

1.
(e)
2.
(b)
3.
(b)
4.
(b)
5.
(b)
6.
(c)
7.
(a)
8.
(c)
9.
(a)
10.
(c)
11.
(d)
12.
(c)
13.
(c)

14.
(d)
15.
(b)
16.
(a)
17.
(c)
18.
(b)

19.
(c)
20.
(c)

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