DP CHEMISTRY SL/HL
Summative Assessment
TOPIC 7: Equilibrium
1.
A.
B.
C.
D.
Which statement is correct for a reversible
reaction when KC ≫ 1 ?
The reaction almost gone to completion.
The reaction hardly occurs.
Equilibrium is reached in a very short time.
At equilibrium, the rate of the forward
reaction is much higher than the rate of the
backward reaction.
Marks: ____/[ ]
5. What happens to the position of the
equilibrium and the value of KC when the
temperature is increased in the following
reaction?
2. Which statement is always correct for a
chemical reaction at equilibrium?
A. The rate of the forward reaction equals the
rate of the reverse reaction.
B. The amount of the products and reactants
are equal.
C. The concentration of the reactants and
products are constantly changing.
D. The forward reaction occurs to a greater
extent than the reverse reaction.
3. Iron(III)ions, Fe3+ , react with thiocyanate ions,
SCN-, in a reversible reaction to form a red
solution. Which changes in the equilibrium will
make the solution go red?
I.
II.
III.
A.
B.
C.
D.
Increasing the temperature.
Adding FeCl3 .
Adding a catalyst.
I and II only.
I and III only.
II and III only.
I, II and III.
4. Which statement about dynamic equilibria
implies they are dynamic?
A. The position of the equilibria constantly
changes.
B. The rates of the forward and backward
reaction changes.
C. The reactants and products continue to
react.
D. The concentrations of the reactants and
products continue to change.
Name: _______________
Position of
Equilibrium
Value of KC
A
Shifts towards
reactants.
Decreases
B
Shifts towards
reactants.
Decreases
C
Shifts towards
products.
Decreases
D
Shifts towards
products.
Decreases
6. Which factor does not affect the
position of the equilibrium in this reaction?
A.
B.
C.
D.
Change in volume of the container.
Change in temperature.
Addition of catalyst.
Change in pressure.
7. Consider the reaction between gaseous
iodine and gaseous hydrogen.
Why do some collisions between iodine
and hydrogen not result in the formation of
the product?
A.
B.
C.
D.
The iodine and hydrogen molecules
do not have sufficient energy.
The system is in equilibrium.
The temperature of the system is too
high.
The activation energy of the reaction
is very low.
8. Consider the equilibrium between N2 O4(g)
and NO2(g).
Which changes shift the position of the
equilibrium to the right?
I.
Increasing the temperature.
II.
Decreasing the pressure.
III. Adding a catalyst.
A.
B.
C.
D.
I and II only.
I and III only.
II and III only.
I, II and III.
9. The equilibrium constant for the reaction
below is K.
What is the equilibrium constant for the
following reaction?
A.
B.
C.
D.
K
2K
K2
2K2
10. What is the equilibrium constant
expression, KC ,for the following reaction?
11. Consider the following reaction:
Which statement is correct when the reaction
is at equilibrium?
A. [A] ≥ [C]
B. [A] > [C]
C. [A] = [C]
D. [A] < [C]
12. What will happen if the pressure is
increased in the following reaction
mixture at equilibrium?
A. The equilibrium will shift to the left and
the pH will decrease.
B. The equilibrium will shift to the right and
the pH will decrease.
C. The equilibrium will shift to the left and
the pH will increase.
D. The equilibrium will shift to the left and
pH will decrease.
13. Which change will favor the reverse
reaction in the equilibrium?
A.
B.
C.
D.
Adding OH- (aq)
Adding H+ (aq)
Increasing the concentration of
CrO42- (aq)
Decreasing the temperature of the
solution.
14. An increase in temperature increases the
amount of chlorine present in the following
equilibrium.
What is the best explanation for this?
A. The higher temperature increases the
rate of the forward reaction only.
B. The higher temperature increases the
rate of the reverse reaction only.
C. The higher temperature increases the
rate of both reactions but the forward
reaction is affected more than reverse.
D. The higher temperature increases the
rate of both reactions but the reverse
reaction is affected more than forward.
Explain:
15. Which equilibrium reaction shifts to
the product side when the temperature
is increased at constant pressure and to
the reactant side when the total pressure
is increased at constant temperature?
v) Explain why solid sodium chloride does not
conduct electricity but molten sodium
chloride does. (Refer back to Topic 4) [2]
Total for MCQ: _____/15
1.
Consider the following equilibrium:
i)
Deduce the equilibrium constant
expression, KC , for the reaction.
[1]
2. The manufacture of gaseous methanol
from CO and H2 involves an equilibrium
reaction.
ii)
State and explain the effect of
increasing the temperature on the
yield of sulfur trioxide.
[2]
State:
Explain:
i)
Outline the characteristics of chemical
equilibrium.
[2]
ii)
a)
State and explain the effect of the
following changes on the equilibrium
position:
Increase in temperature.
[2]
b)
Increase in pressure.
iii) State the effect of a catalyst on the value
of KC .
[1]
iv) State and explain the effect of a catalyst
on the position of the equilibrium.
[2]
State:
[2]
c) Addition of a catalyst.
iii) Predict what would happen to the position
of equilibrium and the value of KC if the
pressure is increased from 1 atm to 2 atm. [2]
3. An example of a homogenous reversible
reaction is the reaction between hydrogen
and iodine.
Propane can be formed by the
hydrogenation of propene.
i)
Outline the characteristics of a
homogenous chemical system that is
in a state of equilibrium.
[2]
4. The Contact process involves an exothermic
reaction.
a)
Deduce the extent of the reaction at
200˚C and 1 atm.(Complete blanks)
[1]
Use the following headings to help you
formulate your answer.
Homogenous chemical system:
Concentration of __________________ is much
higher than the concentration of
_______________________ .
Reaction is almost gone to __________________.
Position of the equilibrium lies very far to the
_____________ .
Dynamic equilibrium:
b) The Contact process operates at a
temperature of 450˚C and a pressure of 2 atm
as optimum conditions for the production of
SO3 . Outline the reasons for choosing these
conditions.
[4]
Concentration of reactants and products:
Temperature: (Complete the missing words)
Rate of reaction is ___________ at low
temperatures, and _________ at high
temperatures.
Forward reaction is __________thermic and
reverse reaction is _________thermic.
High temperatures shift equilibrium to
________, and the ____________ reaction is
favored.
Low temperatures shifts equilibrium to
____________, and favors the ___________
reaction.
450˚C produces good equilibrium yield at a
reasonably fast rate.
ii) Deduce the expression for the
equilibrium constant expression, KC . [1]
c) H2O (g) is removed from the system.
Pressure: (Complete the blanks)
Rate of reaction/ production is __________
(fast/slow) at low pressure, and __________
(fast/slow) at high pressure.
_________ (more/less) moles of gaseous
reactants, _____________ (more/less) moles of
gaseous products.
High pressure shifts the equilibrium to
_____________, and favors the _____________
reaction.
Low pressure shifts equilibrium to
____________, favors the _______________
reaction.
Good reaction rate or high yield is obtained
even at __________ (low/high) pressure.
_________(high/low) pressure is dangerous
and expensive.
d) A catalyst is added to the reaction mixture.
iii) Define the term activation energy, Ea.
[1]
Minimum energy needed...
5. Consider the following equilibrium:
iv) Define the term endothermic reaction.
[1]
v) Define the term rate of reaction.
[1]
Nitrogen reacts with hydrogen to form
ammonia in the Haber process, according
to the following equilibrium.
i)
Deduce the equilibrium constant
expression for the reaction.
[1]
Rate of change of _______________________.
Change in ___________________ of
product/reactant with _______________.
ii)
a)
Predict the direction in which the
equilibrium will shift when the
following changes occur:
The volume increases.
b)
The temperature decreases.
[4]
Total Mark for Part B: ______/32