Name: ___________________________________________ Period: _____ Teacher: ______________
Reaction Rate (Pre-AP)
27
28
29-30
31
3
4
5-6
7
What is Reaction
Rate?


Explain what is happening on a
molecular level when a reaction is
occurring and understand that
orientation of the molecules, speed and
concentration affect the rate.
Define: reaction rate, collision theory,
activation energy, activated complex,
reversible reaction.
Factors that
Affect Rate



List the 5 factors that
affect rate: nature of
reactants, temperature,
surface area, catalyst and
concentration.
Explain the role of a
catalyst.
Perform experiment and
graph the data to show
concentration of reactant
vs. time of reaction.
Reaction Progress
Graph


Label a graph depicting the energy
vs. time of a reaction, initial energy,
final energy of products, activation
energy, H, activated complex.
Determine if a reaction is
endothermic or exothermic from a
reaction progress graph.
Experimental Data






Calculate average rates of chemical
reactions from experimental data.
Determine reaction orders using the
method of initial rates
Calculate instantaneous rates of
chemical reactions.
Understand that many chemical
reactions occur in steps.
Relate the instantaneous rate of a
complex reaction to its reaction
mechanism.
Determine the rate law of a reaction with
a complex mechanism using the slowest
step.
Rate Relationships


Relate rates of chemical reactions to
collisions between reacting particles.
Express the relationship between
reaction rate and concentration.
Rate Law and Reaction
Order – Khan Academy
Experimental
Determination of Rate
– Khan Academy
Warm-ups
Mon, March 27
Tues, March 28
Wed, March 29
Fri, March 30
Mon, April 3
Tues, April 4
Wed, April 5
Fri, April 7
Practice Determining Rate Laws:
1.
2A + B
[A]
1
0.1
2
0.1
3
0.2
Determine the rate law:
2C
[B]
0.2
0.4
0.4
Rate
0.10
0.20
0.80
AB
[A]
Rate
1
0.05
3.0 x 10-4
2
0.10
1.2 x 10-3
3
0.20
4.8 x 10-3
Determine the rate law:
3.
5.
1
2
3
A + 2B 2C
[A]
[B]
1
0.1
0.1
2
0.2
0.1
3
0.2
0.3
Determine the rate law:
2.
Rate
0.10
0.20
0.60
A + 2B 2C
[A]
[B]
Rate
1
0.10
0.20
1.0 x 10-5
2
0.20
0.20
1.0 x 10-5
3
0.20
0.40
2.0 x 10-5
Determine the rate law:
4.
NH4+ + NO2-  N2 + 2H2O
Determine the rate law:
Rate
[NH4+] [NO2-]
(mol/L•min)
0.100
0.005
1.35 x 10-7 Determine the value of k and its units:
0.100
0.010
2.70 x 10-7
0.200
0.010
5.40 x 10-7
6. The reaction CH3COCH3 + I2  CH3COCH2I + HI is run under carefully controlled conditions in the
presence of an excess of acid. The following data were obtained:
A. Write the rate law for the reaction.
[CH3COCH3]
0.100 M
0.0500 M
0.0500 M
[I2]
0.100 M
0.100 M
0.200 M
Initial Rate
1.16 x 10-7mol/Ls
5.80 x 10-8 mol/Ls
5.80 x 10-8 mol/Ls
B. Calculate the value of the rate constant and its units.
C. What would be the initial rate if the concentrations of [CH3COCH3] and [I2] were each 0.300 M?
Chapter 19 Worksheet #1
NO2 + O2  2N2O5
Trial #
Initial [NO2]
1
0.025
2
0.025
3
0.050
Initial [O2]
0.011
0.022
0.011
Initial Rate of formation of N2O5
3.1 x 10-4 mol/Ls
6.2 x 10-4 mol/Ls
6.2 x 10-4 mol/Ls
1. Write the rate law expression for the reaction.
2. Calculate the value of the rate constant and specify its units.
3. Use the rate law expression and calculated value of k to compute the initial rate of formation of N2O5, if the
initial concentrations of NO2 and O2 were each 0.030M.
C2H4O  CH4 + CO
Trial # Initial[C2H4O]
1
0.001412
2
0.002824
Initial Rate in mol/Ls
3.451 x 10-5
6.902 x 10-5
4. Write the rate law for the above reaction.
5. Calculate the value of the specific rate constant and specify its units.
A+BC
Trial # Initial [A]
1
0.20
2
0.20
3
0.40
Initial[B]
0.20
0.40
0.40
Initial rate of formation of C in mol/L•min
2.0 x 10-4
8.0 x 10-4
1.6 x 10-3
6. Determine the rate law for the above reaction.
7. Calculate k and specify its units.
8. If the initial concentrations of both A and B are 0.30 M, at what initial rate is C formed?
5. Explain how the following mechanism can be used to determine the rate expression for a chemical reaction A
+ 2B → AB2.
Step 1
B + B → B2 slow
Step 2
B2 + A → AB + B
fast
Step 3
B + AB → AB2
fast
6. What is the rate law expression for the following mechanism?
Step 1
AB + C2 → AC2 + B
Step 2
B + AB → AB2
Step 3
AC2 + AB2 → A2C2 + B2
Step 4
A2C2 + B2 → A2C + B2C
slow
fast
fast
fast
7) The rate of the reaction shown below was studied: 2 NO + H2 → N2O + H2O
It was found that the rate doubled when the [H2] was doubled.
It was also found that the rate increased by a factor of four when the NO concentration was doubled.
Which of the following mechanisms is/are consistent with these data?
A) step 1
NO + H2 → N + H2O
(slow)
step 2
N + NO → N2O
B) step 1
NO + NO ⇄ N2O2
step 2
N2O2 + H2 →N2O + H2O
(slow)
C) step 1
H2 + 2NO → N2O + OH + H (slow)
step 2
OH + H → H2O
D) step 1
NO + NO→ NO2 + N
(slow)
step 2
NO2 + H2 → NO + H2O
step 3
N + NO → N2O
Concepts
1. Discuss two possible ways to determine the average rate of the following reaction in the laboratory. What
quantities would you measure in each case?
H2(g) + I2(g)  2HI(g)
2. In the reaction A + B  C, the concentration of A decreases from 6.2710−2 mol/L to 4.75102 mol/L in a
span of 125 s. What is the rate of the reaction in terms of reactant A?
3. The collision theory says that particles must collide in order to react. What other two requirements must be
met in order for particles to react?
4. Explain why increasing the concentration of a reactant usually increases the rate of a chemical reaction.
5. The rate law of the reaction Q + R  QR is rate = k[Q]2[R]. How will the rate of the reaction change if [Q] is
doubled? Explain.
6. Explain how the rate-determining step of a complex reaction controls the overall reaction rate.
PreAP Review – Chapter 16 [Rate]
Note, this review may or may not cover all material on the test. Students are expected to thoroughly review all notes,
worksheets, and moodles to prepare for the test. This document merely provides additional focused practice.
Label the graph with the following terms:
reactants, products, activation energy (no catalyst), Answer the questions below about the reaction progress graphs.
activation energy with catalyst, ∆H or overall
change in enthalpy,
a) Is this endo or exothermic?
b) Is ∆H negative or positive?
1) Why do you think a chapter about reaction rate is sometimes called “chemical kinetics”?
2) What must be true on a molecular level in order for a reaction to occur?
3)
a.
b.
c.
d.
Rate of reaction tends to slow down over time due to:
Decrease of reactant concentration
Decrease in product
Lack of activation energy
Both A and B
6)
a.
b.
c.
d.
A catalyst works by:
Lowering the activation energy barrier
Raising the activation energy barrier
Changing the particle size of the reactants
Shifting the equilibrium toward the products
4)
a.
b.
c.
d.
A formula in brackets, for example [HCl] indicates:
HCl is a catalyst
HCl is a product
The concentration in molarity
The concentration in molality
7)
a.
b.
c.
d.
The rate of a chemical reaction normally:
Increases as temperature increases
Increases as particle size increases
Decreases with increased reactant concentration
Is slowed down by a catalyst
5) If a reaction has a rate of 0.500 M/s at 280 K, what is a
good guess for its rate at 290 K?
a .2.00 M/s
b. 1.00 M/s
c. 0.500 M/s
d. 0.250 M/s
8) Which of the following is the rate law for this
elementary (or single step) reaction?
2A + B  2C + 2D
a.
b.
c.
d.
Rate = k[A]2[B]
Rate = k[A]2[B]*[C]2[D] 2
Rate = k[A]2[B] ÷ [C]2[D] 2
Rate = k[C]2[D] 2
9) The formula above shows the rate law for a certain
reaction. Which of the following gives the correct result
when the concentration of NO is doubled?
a. The reaction rate is unaffected.
b. The reaction rate doubles.
c. The reaction rate triples.
d. The reaction rate quadruples.
10) The rate of reaction can never proceed faster than that
of the rate-determining step because _________.
a. the rate-determining step must exceed the rate of
reaction
b. all rate-determining steps require a catalyst
c. the rate-determining step is always the first step in
any reaction
d. the rate of reaction is always limited by the slowest
overall step
11) Reactions may be classified with an overall order, as
well as orders with respect to the individual substances
reacting. Which of these is classified as third order overall?
a. Rate = k[A]2[B][C]
b. Rate = k[A]3[B]
c. Rate = k[A]2[B]
d. Rate = k[B]3[C]
12) The table below shows the various conditions used
when four students dissolved sugar. The student whose
sample will dissolve the fastest is most likely _________.
a. Hema
b. Aaron
c. Nikki
d. Erick
13) Which of the following would NOT increase the rate of
a reaction?
a. an increase in the concentration of reactants
b. the removal of a catalyst
c. an increase in solvent volume
d. an increase in temperature
14)
If a reactant is first order, and you triple the
concentration of it, what should happen to the overall rate?
a. Quadruples it
b. Triples it
c. Doubles it
d. No change
15)
Quadrupling the concentration of a zeroth order reactant changes the reaction rate how?
a. Quadruples it b. Triples it c. Doubles it d. No change
16)
Which does not affect the reaction rate of a reaction?
a. concentration b. humidity c. surface area d. temperature
17)
_________is determined by finding the slope of the straight line tangent to the curve of a plot of the change in
concentration of a reactant versus time.
a. instantaneous rate b. average rate c. method of initial rate d. best guess
18)
A ____is a reactant in one reaction in a complex mechanism and then canceled as a product in a later step in
the reaction.
a. catalyst b. intermediate c. reactant d. activated complex
19)
Methane soap bubbles burn but children’s bubbles do not this is due to:
a. catalyst b. particle size c. temperature d. concentration e. nature of reactants
Proposed Complex Mechanism: 2NO  N2O2
20)
21)
22)
23)
(slow)
N2O2 +H2 N2O + H2O
(fast)
N2O +H2  N2 + H2O
(fast)
What is the overall reaction?
Estimate the rate law:
What are the intermediates or catalysts? ( Identify each particle)
What will the graph of the three reactions look like?
Workout Problems:
Consider the following reaction and the data collected from a series of rate experiments:
Experiment 1
Experiment 2
Experiment 3
Experiment 4
[N]
[H]
[NH]
Rate (M/s)
3.00
3.00
6.00
3.00
2.00
4.00
2.00
2.00
1.00
1.00
1.00
2.00
2.00
4.00
8.00
2.00
24) Write the rate law for this equation
25) What is the order for [N]?
26) What is the overall order for the rate law?
27) Find K, the rate constant, including correct units. (show all work for credit)
28)
The orders are given for the reactants below A, B, C, and D
1nd Order
1st Order
0 order
2nd order
Rate M/sec
Reactants
[A]
[B]
[C]
[D]
Exp 1
2
2
2
2
4.50
Exp 2
3
6
9
3
45.56
Exp 3
4
4
3
6
162
Exp 4
4
4
4
4
?
Exp 5
8
8
8
8
?
Solve for k in the first experiment, and use that value to calculate the rate in experiment 4 a