Chapter 7 Review (7.1 – 7.4)
Name: _________________________________
Date: _______________________
Marking Scheme:
A
B
C
D
E
F
total
8
14
10
5
55
3
15
A.
Multiple Choice. Identify the letter of the choice that best completes the statement or answers the question.
____
1.
____
2.
For the equilibrium system below, which of the following would result in an increase in the
quantity of PCl5(g)? PCl3(g) + Cl2(g) <=====> PCl5(g) + 45 kJ
a. increasing temperature
d. removing some Cl2(g)
b. increasing the size of the container
e. injecting some He gas
c. decreasing temperature
a.
b.
c.
d.
e.
Some CO2 is removed from the equilibrium system shown below. Which of the following
statements is/are true when the equilibrium responds to this stress?
CO(NH2)2(g) + H2O(g) + 45 kJ <=====> CO2(g) + 2 NH3
heat is released as the equilibrium shifts to replace the removed CO2
the quantity of NH3 will rise
the quantity of H2O(g) will rise
both a and b are true
both b and c are true
____
a.
3.
If at equilibrium 1.0 mol of CH3OH is still in the container the K must be which of the following?
b. 125
c. 0.0080
d. 12.5
e. 0.032
25
____
1.2 mol of CH3OH(g) are injected into a 2.0 L container and the following equilibrium becomes
established: 2H2(g) + CO(g) <=====> CH3OH(g) + 92 kJ
4.
A flask contains this equilibrium:
Fe3+(aq) + SCN1-(aq) <======> FeSCN1-(aq)
(yellow)
(colourless)
(dark red)
What is observed if a few drops of iron(III) chloride is added to this equilibrium?
a. it becomes darker red
d. nothing happens
b. it becomes lighter red
e. none of the above
c. it becomes colourless
____
5.
A full syringe contains this equilibrium:
2 NO2(g) <======> N2O4(g)
If nitrogen dioxide gas is brown and the other gas is colourless, what is observed when the
syringe is used to compress this gas mixture?
a. the mixture gets darker
d. the mixture gets lighter
b. the mixture gets darker then lighter
e. none of the above
c. the mixture get lighter then darker
____
6.
____
7.
The Haber Process was used to vastly improve the production of ammonia, which is needed for
the production of:
a. fertilizers and explosives
d. hydrogen and nitrogen gas
b. catalysts and cement
e. cement and explosives
c. cement and fertilizer
Consider this equilibrium: N2(g) + H2(g)
NH3(g) + 94 kJ
The equilibrium law expression for the balanced chemical equation would be
a. [N2][H2] / [NH3]
d. [NH3]2 / [H2]3[N2]
b. [NH3] / [H2][N2]
e. 2[NH3]2 / 3[H2]3[N2]
2
c. [NH3] / [H2][N2]
____ 8.
Which of the following conditions must be met if dynamic equilibrium is to be maintained?
a. the system must be closed
b. the system must be reversible
c. the rate of the forward reaction is equal to the rate of the reverse reaction
d. all of the above
e. just b and c are true
B.
Write an example of solubility equilibrium, phase equilibrium and chemical reaction equilibrium.
C.
The Equilibrium Constant
1. Write equilibrium (K) equations for the following: (3)
a) NH4Cl(s) <---> NH3(g) + HCl(g)
b) PbF2(s) <---> Pb2+(aq) + 2 F-(aq)
c) 4 HCl(g) + O2(g) <---> 2 H2O(g) + 2 Cl2(g)
For part c), determine the K value if [HCl] = 0.25
mol/L; [O2] = 0.10 mol/L; [H2O] = 0.50 mol/L
and [Cl2] = 0.75 mol/L. Does the reaction favour
the products or the reactants?
2. For the reaction CO(g) + 2 H2(g) <---> CH3OH(g) + heat;
[CO(g)] = 0.025 mol/L, [H2(g) ] = 0.050 mol/L and [CH3OH(g)] = 0.0063 mol/L
a) determine K (2)
b) determine K’ (K for the reverse reaction) (2)
c) If only CH3OH(g) is added to the vessel, will the same K value eventually be reached? (1)
3. The graph shows the concentration of gases in a sealed reaction vessel for the following system:
N2(g) + 3 H2(g) <---> 2 NH3(g) + energy
a)
b)
c)
A
D.
B
Describe what happens from time A to just prior
to time B. (2)
At time B, NH3 is removed from the container.
What happens from time B to time C? (2)
List 3 other ways of keeping this reaction moving
forward in order to produce ammonia. (3)
C
Equilibrium problems:
1. For the equation:
2 HI(g) <=====> H2(g) + I2(g)
5.00 mol of hydrogen iodide gas are introduced into a 2.00 L container and heated. At equilibrium, 1.50
mol of hydrogen iodide gas remain in the container.
a)
b)
c)
d)
Use an ICE table to determine the equilibrium concentrations of hydrogen and iodine gas. (3)
Calculate the percent reaction at equilibrium. (2)
Determine K at equilibrium. (2)
Does this reaction favour reactants or products? (1)
2.
Consider the following equilibrium:
H2(g) + I2(g)
2HI(g)
If 1.2 mol of H2 and 1.2 mol of O2 was placed in a 1.0 L container and allowed to reach equilibrium,
what would the value of Keq be if at equilibrium [HI] = 0.40 mol/L? (3)
3. The equilibrium system shown below has a Kc = 1.4 x 10-4. If [A] = 0.24 mol/L, what is the [D]? (3)
3A(g) + B(s)
E.
Le Châtelier’s Principle.
Stress system
Change
+ = forward
Ø = no change
— = reverse
Reaction:
Explanation
C(s) + 2D(g)
2 SO2(g) + O2(g) <=====> 2 SO3(g) + heat
change in concentration after
system has been stressed
SO2(g)
O2(g)
change in
Kc
SO3(g)
Add O2(g)
Add SO3(g)
Remove SO2(g)
Decrease Temp
Increase Volume
Add Catalyst
F.
The Haber Process involves the following closed gaseous system: N2(g) + 3 H2(g) <---> 2 NH3(g) +
energy. What conditions did Haber change to drive this reaction forward. From a chemical engineering
standpoint, what is the greatest challenge of this process?