Chemistry 12
Unit 1 – Provincial Practice Questions WR
Chemistry 12
Unit 1 – Provincial Practice Questions (Written Response)
1. Using collision theory, give two reasons why an increase in temperature results in an
increase in reaction rate.
1. higher probability of collisions
2. larger fraction of successful collisions
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2. Consider the following reaction:
C(s) + O2(g) --> CO2(g)
State three factors that would increase the rate of the above reaction. Use collision theory to
explain the increase in rate.
1. ________________________________________-Explanation _____________________
_______________________________________________________________________
2. ________________________________________-Explanation _____________________
_______________________________________________________________________
3. _______________________________________-Explanation _____________________
_______________________________________________________________________
3. Define the term activation energy.
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Unit 1 – Provincial Practice Questions WR 3/3/2016
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Unit 1 – Provincial Practice Questions WR
Chemistry 12
4. Consider the following overall reaction:
2NO + 2H2 --> 2H2O + N2
a) Explain why the reaction is likely to involve more than one step.
b) A proposed mechanism for the reaction is:
Step 1:
NO + H2  N + H2O
Step 2: NO + N  N2O
Step 3: ???
Write the equation for Step 3.
_______________________________________
c) Give the formula for the activated complex in Step 1 _______________________
d) Give the formula for the activated complex in Step 3 _______________________
e) Identify two reaction intermediates ___________ and _____________
5. Consider the decomposition of ammonia:
2 NH3(g) --> N2(g) + 3 H2(g)
When 1.0 mole NH3 reacts, 46 kJ of energy is absorbed. Rewrite the equation for this reaction,
including the value of the heat term.
_______________________________________________________________________
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Unit 1 – Provincial Practice Questions WR
Chemistry 12
6. Consider the following reaction mechanism:
Step 1: ClO2(g) + F2(g) --> FClO2(g) + F(g)
Step 2:
F(g) + ClO2(g) --> FClO2(g)
(slow)
(fast)
a) Write the equation for the overall reaction. ________________________________________
b) Identify a reaction intermediate. ____________________________________________
c) If some F2 was introduced into the reaction chamber, would the overall reaction rate increase?
_________________Explain why or why not. _______________________________________
____________________________________________________________________________
d) If some F was introduced into the reaction chamber, would the overall reaction rate increase?
_________________Explain why or why not. _______________________________________
___________________________________________________________________________
e) Write the formula for the activated complex in Step 1. _________________________________
f) Is there a catalyst in this mechanism? . ______________________________________
g) The rate determining step is step _________
7. A strip of magnesium was cut into 4 pieces, each of length 1.0 cm and mass of 0.00972 g. Each
piece was placed into a test tube containing 5.0 mL of different concentrations of HCl. The time
required for each piece of magnesium to be completely consumed was recorded:
Trial [HCl](M) Time (s)
1
0.50
200
2
1.0
38
3
3.0
12
4
6.0
6
a) Calculate the rate of reaction for magnesium in 3.0 M HCl.
b) How does the [HCl] affect the reaction rate?
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Chemistry 12
c) Give a reason for your answer for (b) using collision theory
Unit 1 – Provincial Practice Questions WR
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8. Consider the following potential energy diagram for a reversible reaction:
a) Determine the activation energy for the forward reaction. ______________
b) Determine H for the forward reaction _____________
c) Determine the activation energy for the reverse reaction. ________________
d) Which reaction, the forward or the reverse would have the faster rate? ________
Explain your answer The forward rx has the lower activation energy so it will have the faster
rate
e) A catalyst can be added to this reaction. The catalyzed mechanism has two steps. The
first step is fast and the second step is slow. On the graph above, show the curve for the
catalyzed reaction with a dotted line.
9. A student wishes to monitor the rate of the following reaction:
Cu(s) + 4HNO3(aq) --> Cu(NO3)2 (aq) + 2NO2(g) + 2H2O(l) + heat
colourless
blue
brown
Identify 3 different properties that could be used to monitor the rate of the reaction.
Describe and explain the changes that would occur.
Property 1 ________________________________. Changes that occur as the reaction
proceeds. ____________________________________________________________
Property 2 ________________________________. Changes that occur as the reaction
proceeds. ____________________________________________________________
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Chemistry 12
Unit 1 – Provincial Practice Questions WR
Property 3________________________________. Changes that occur as the reaction
proceeds. ____________________________________________________________
10. Consider the following reaction:
2Fe(s) + 6HCl(aq) --> 2FeCl3(aq) + 3H2(g)
A 0.037 g sample of Fe reacts completely with HCl in 18.3 s. Calculate the volume of H2(g)
produced in 4.0 minutes. Show all your work. Assume the gas is at STP.
11. Consider the reaction:
2H2O(l) --> 2H2(g) + O2(g)
The rate of production of O2 is 2.3 x 10-2 mol/s . How many seconds will it take to
decompose 85.0 g of H2O? Show all of your work in a clear manner.
12. Define the term heterogeneous reaction. _________________________________
________________________________________________________________
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What factor affects the rate of only heterogeneous reactions? _________________
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Chemistry 12
Unit 1 – Provincial Practice Questions WR
13. The release of O2(g) resulting from the decomposition of bleach was measured in two
different experiments. Data was collected and the following graph was drawn:
a) Calculate the average rate of reaction for each experiment.
Rate of Experiment 1:
Rate of Experiment 2:
b) Identify a variable from Experiment 1 and how it was changed to produce the different
reaction rate for Experiment 2. Explain using collision theory.
Either the concentration of bleach or the temperature could be decreased. Both would
decrease the number of possible collisions, and a decrease in temperature would
decrease the fraction of successful collisions.
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