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Review Topic 11: Reaction Rates and Equilibriums
Name: Score: 19 / 19 points (100%)
Review Topic 11: Reaction Rates and Equilibriums
Multiple Choice
Identify the choice that best completes the statement or answers the question.
B 1. a. 1
b. 2
B 2. c. 3
d. 4
ANSWER: B
Catalyst lower the activation energy and the activation energy is located at the
top of the curve.
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Review Topic 11: Reaction Rates and Equilibriums
a.
b.
A 3. ANSWER: B
To double the rate at 20 degrees, we must go from a rate of 1 to 2. The
temperature that corresponds to 2 is 40 degrees and the difference between the
two temperatures is 20.
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a. are condensing at the same rate that
others are evaporating
b. cease to form when the air in the jar
becomes saturated
4. c.
d.
c. are evaporating faster than they are
condensing
d. form only at high temperatures
ANSWER: A
At equilibrium, the forward rate is equal to the reverse rate, so the rate of
condensation equals the rate of evaporation.
POINTS: 1 / 1
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Review Topic 11: Reaction Rates and Equilibriums
A a.
c.
b.
d.
ANSWER: A
When dealing with equilibriums, the system has to be closed, so choices B and
D are eliminated. A is the best choice because it shows the movement of the
gas and liquid particles.
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B 5. Which of the following occurs when a reaction in a solution is at equilibrium and
more product is added to the solution?
a. Equilibrium shifts to produce more product
b. Equilibrium shifts to produce more reactant
c. No change will occur
d. The reaction will stop
B 6. ANSWER: B
Le Chatelier’s Principle ­ adding product causes the reaction to shift to the
reactants.
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Which condition will cause a shift in the equilibrium of the above reaction?
a. Double the concentration of reactants and products
b. Increase the reaction temperature
c. Reduce the concentration of products and reactants by 10%
d. Keep the reaction temperature constant
ANSWER: B
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A 7. Review Topic 11: Reaction Rates and Equilibriums
a ­ has no effect because no relative concentrations are changed
b ­ has effect because a temperature change will effect on side more than the
other
c ­ has no effect because no relative concentrations are changed
d ­ has no effect because nothing is changed
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Calcium carbonate was placed in a flask on a balance, and dilute hydrochloric acid
was added. Carbon dioxide that was produced escaped from the flask. The total mass
of the flask and its contents was recorded every 10 seconds. The diagram above
shows a plot of the results. Between which of the following times was the reaction the
fastest?
a. 0 and 10 seconds
c. 20 and 30 seconds
b. 10 and 20 seconds
d. 30 and 40 seconds
ANSWER: A
The fastest rate is at the beginning so from time 0 to 10 seconds
POINTS: 1 / 1
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Review Topic 11: Reaction Rates and Equilibriums
D 8. Catalytic converters made of palladium (Pd) reduce automobile pollution by
catalyzing the reaction between unburned hydrocarbons and oxygen. How does Pd
increase the rate of this reaction?
a. By cooling the reactants
b. By splitting the oxygen atoms
c. By giving the hydrocarbons a negative charge
d. By decreasing the activation energy
ANSWER: D
Catalyst always lower the activation energy
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C 9. The role of a catalyst is to affect ­­
a. electronegativity
c. activation energy
b. heat content
d. ionization energy
C 10. ANSWER: C
Catalyst always lower the activation energy so it affects the activation energy.
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NO2 and N2O4 undergo the reaction shown. When a sealed container of NO2 reaches
chemical equilibrium, which must be true?
a. No N2O4 is present.
b. No chemical reactions are occurring.
c. The rates of the forward and reverse reactions are equal.
d. The maximum number of molecules has been reached.
ANSWER: C
At equilibrium, the rates are equal.
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C 11. A catalyst is a substance used in chemical reactions to —
a. provide a higher activation energy pathway
b. decrease collisions between reactant molecules
c. increase the rate of the reaction
d. change the equilibrium to favor products
ANSWER: C
a . provide a higher activation energy pathway ­ not true (lowers it)
b. decrease collisions between reactant molecules ­ not true (holds them so it
increases)
c. increase the rate of the reaction d. change the equilibrium to favor products ­ not true (does not effect
equilibrium concentrations)
POINTS: 1 / 1
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D 12. Review Topic 11: Reaction Rates and Equilibriums
Na2S2O3 (aq) Na2SO3 (aq) + S(s)
In the above reaction, a cloudiness at completion due to colloidal suspension of sulfur
appears. If the reaction is carried out at various temperatures, at which temperature
would it proceed at the fastest rate?
a. 20C
c. 40C
b. 30C
d. 50C
ANSWER: D
Reaction rate increases with temperature
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C 13. A heated liquid placed in a closed container will vaporize until —
a. the boundary between liquid and vapor disappears
b. all the liquid molecules become vapor molecules
c. the number of liquid molecules vaporizing equals the number of vapor molecules
condensing
d. the vapor pressure is greater than the atmospheric pressure
ANSWER: C
The answer is it will go to equilibrium ­ which is the rate forward equals the
rate in reverse. C is the only one that describes this.
POINTS: 1 / 1
B 14. Each beaker shown above contains 2.2 grams of iron and 1 liter of 3M H2SO4 at STP.
Which reaction will go to completion first and why?
a. Beaker A because of increased surface area
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Review Topic 11: Reaction Rates and Equilibriums
b. Beaker B because of increased surface area
c. Beaker A because of a higher concentration level
d. Beaker B because of a higher concentration level
ANSWER: B
C and D are out because they have an equal concentrations
B has a higher surface area than A because it is ground up
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C 15. In the reaction 2SO2 (g) + O2 (g) 2SO3 (g), which change would cause the greatest
increase in the concentration of SO3?
a. Decrease the concentration of SO2
c. Increase the concentration of SO2
b. Decrease the concentration of O2
d. Increase the concentration of O2
ANSWER: C
Le Chatelier’s Principle ­ to increase product concentration increase reactants
(decreasing reactants would cause the products to decrease too)
The bigger the coefficient in front of the reactant, the bigger an effect it will
have
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C 16. If the temperature of a reaction is increased, the reaction proceeds at a much quicker
rate because the —
a. activation energy increases
b. energy of the products increases
c. frequency of collisions between reactants increases
d. energy of the activated complex increases
B 17. ANSWER: C
increase energy increases motion which increases collisions
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N2(g) + 3F2(g) 2NF3(g)
Equilibrium has been reached for the reaction shown. Which conclusion is correct?
a. The N2 and F2 together will form at a faster rate than the NF3.
b. The partial pressures of N2, F2, and NF3 will stay constant.
c. The NF3 will form at a faster rate than the N2 and F2 together.
d. The partial pressure of NF3 will keeping changing.
ANSWER: B
Equilibrium is when the forward and reverse rate are equal. With this in mind
choice a and c could not be the answer. And according to Le Chatelier’s
principle, changing the pressure of a system would add stress that would result
in the equilibrium to shift. As a result, d would not be an option because this
would mean that it wouldn’t be in equilibrium. b would have to be the answer
because the equal rates would keep the pressures constant.
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18. Which of these correctly describes how organic catalysts operate in biological reactions?
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C Review Topic 11: Reaction Rates and Equilibriums
a.
b.
c.
d.
They are used up in the reactions.
They lower the overall energy of the reactions.
They lower the activation energy of the reactions.
They keep the temperature of the reactions constant.
ANSWER: C
Catalyst speed up the reaction by lowering the activation energy.
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Multiple Response
Identify one or more choices that best complete the statement or answer the question.
19. A change in which of these could affect the chemical equilibrium of a closed system?
a. Concentration
d. Volume
b. Pressure
e. Temperature
c. Catalyst
RESPONSE: A,B,D,E
ANSWER: A,B,D,E
This goes back to Le Chatelier’s Principle
Concentration ­ Yes ­ It adds weigh to one side causing the shift
Pressure ­ Yes ­ It is the one that doesn’t use the see saw and it automatically
goes to the side with less gases if pressure is increased
Catalyst ­ This affects the activation energy by lowering it and therefore
make the reaction happen faster, but it does not affect the equilibrium
Volume ­ Yes ­ A tricky one because this will affect the pressure and
therefore affect the equilibrium
Temperature ­ Yes ­ It adds weigh to one side causing the shift
POINTS: 1 / 1
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