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 anincrease in reaction rate.
1.
2.
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.
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 à N + H2O
Step 2: NO + N à 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.
______
6. Consider the following reaction mechanism:
Step 1: ClO2(g) + F2(g) --> FClO2(g) + F(g) (slow)
Step 2: F(g) + ClO2(g) --> FClO2(g) (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 ______
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?
c) Give a reason for your answer for (b) using collision theory
8. Consider the following potential energy diagram for a reversible reaction:
a) Determine the activation energy for the forward reaction. ______
b) Determine DH 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
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. ______
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. ______
______
What factor affects the rate of only heterogeneous reaction? ______
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.
Unit 1 – Provincial Practice Questions WR 9/25/2006 Page 6