SCH4U:
UNIT OVERVIEW ON ENERGY CHANGES AND CHEMICAL REACTIONS
Submitted by: Amarinder Sawhney
Vanessa Poehlmann
Rajni Kant Sharma
UNIT DESCRIPTION
This
unit
involves
the
study
of
thermodynamics, energy changes and Rates
of reaction and factor affecting them. It
involves study of potential energy diagrams
for chemical reactions. Students will learn to
solve the problems based on rates of
reactions , energy changes, hess’s law
OVERALL EXPECTATIONS
D1. analyse technologies and chemical processes that are
based on energy changes, and evaluate them in terms of
their efficiency and their effects on the environment;
D2. investigate and analyse energy changes and rates of
reaction in physical and chemical processes, and solve
related problems;
D3. demonstrate an understanding of energy changes and
rates of reaction.
Specific expectations
D1
D2
D2.1 use appropriate
D1.1 analyse some conventional
terminology related to energy
and alternative energy technologies changes and rates of reaction,
(e.g., fossil fuel–burning power
including, but not limited to:
plants, hydro-powered generators,
enthalpy, activation energy,
solar panels, wind turbines, fuel
endothermic, exothermic,
cells), and evaluate them in terms of potential energy, and specific
their efficiency and impact on the
heat capacity [C]
environment [AI, C]
D2.2 write thermo chemical
D1.2 analyse the conditions (e.g.,
equations, expressing the
temperature, pressure, presence of energy change as a ΔH value or
a catalyst) required to maximize the as a heat term in the equation
efficiency of some common natural [AI, C]
or industrial chemical reactions
(e.g., decomposition, combustion,
D2.3 solve problems involving
neutralization),and explain how the analysis of heat transfer in a
improved efficiency of the reaction
chemical reaction, using the
contributes to environmental
equation Q = m c ΔT(e.g.,
sustainability [AI, C]
calculate the energy released in
the combustion of an organic
compound ,and express the
results in energy per mole of
fuel [J/mol]) [AI, C]
D2.4 plan and conduct an
inquiry to calculate ,using a
calorimeter, the heat of
reaction of a substance (e.g.,
the heat of solution of
ammonium nitrate, or of
combustion of a
hydrocarbon),compare the
actual heat of reaction to the
theoretical value, and suggest
sources of experimental error
[IP, PR, AI, C]
D2.5 solve problems related to
D3
D3.1 compare the energy changes
resulting from physical change
(e.g., boiling water), chemical
reactions (e.g., bleaching a stain),
and nuclear reactions (e.g., fission,
fusion), in terms of whether
energy is released or absorbed
D3.2 compare the energy change
from a reaction in which bonds are
formed to one in which bonds are
broken, and explain these changes
in terms of endothermic and
exothermic reactions
D3.3 explain how mass, heat
capacity, and change in
temperature of a substance
determine the amount of heat
gained or lost by the substance
D3.4 state Hess’s law, and explain,
using examples, how it is applied
to find the enthalpy changes of a
reaction
D3.5 explain, using collision theory
and potential energy diagrams,
how factors such as temperature
,the surface area of the reactants,
the nature of the reactants, the
addition of catalysts, and the
concentration of the solution
control the rate of a chemical
reaction
D3.6 describe simple potential
energy diagrams of chemical
reactions (e.g., the relationships
between the relative energies of
energy changes in a chemical
reaction, using Hess’s law [AI]
reactants and products and the
activation energy of the reaction)
D2.6 conduct an inquiry to test
Hess’s law (e.g., measure heats
of reaction from the
combustion
of magnesium, and combine
them to yield the ΔH value of
the reaction) [PR, AI]
D3.7 explain, with reference to a
simple chemical reaction (e.g.,
combustion), how the rate of a
reaction is determined by the
series of elementary steps that
make up the overall reaction
mechanism
D2.7 calculate the heat of
reaction for a formation
reaction, using a table of
standard enthalpies of
formation and applying Hess’s
law [AI]
D2.8 plan and conduct an
inquiry to determine how
various factors (e.g., change in
temperature, addition of a
catalyst, increase in surface
area of a solid reactant) affect
the rate of a chemical reaction
[IP, PR, AI]
Content
Evaluation code
L= Learning strategies and
A=assessment
E=Evaluation
including criteria
1. Laws of thermodynamics, open
system, closed system
[2 hrs]
D1, D1.1 D2,
D2.1, D3
L=Brain storming on open
and closed system
K/U
A=Alternate- response
Introduction of thermodynamics (heat
reaction changes with closed and
open vessel).
Explain the first law of
thermodynamics by stating: “Energy
cannot be created or destroyed it can
only change forms.” Then explain the
law of thermodynamics in open and
close system by deriving the equation
and with diagram
By the end of the lesson students will
be able to ;
Differentiate between open and close
system in terms of whether the
energy is released or absorbed
2.Enthalpy changes and heats of
reaction
[3 hrs]
Introduction of key concepts related
to heats of reactions pertinent to the
lab activity such as: heats of reactions;
calorimeters; specific heat capacity;
and enthalpy. Explanation of
definition of Enthalpy (H=E+PV) and
describe change in enthalpy equation
H = H products – H reactants
After explaining thermo chemical
equations derive its equations by
expressing the energy change as a ΔH
value or as a heat term in the
equation [AI, C].
Solve numerical problems involving
analysis of heat transfer in a chemical
reaction, using the equation Q = m c
ΔT (e.g., calculate the energy released
in the combustion of an organic
compound ,and express the results in
energy per mole of fuel [J/mol]) [AI, C]
By the end of the lesson students will
be able to calculate;
D2, D3,D2.2,
D2.3, D2.7
L= Start with a think-pairshare question regarding
enthalpy as an energy
change in a reaction
L = Lecture , demonstration
, discussion
A= Numerical problems
K/U , C
Better understand the heat flow
between reactant and product
Heat of reaction for a formation
reaction, using a table of standard
enthalpies of formation.
Heat of a reaction using a calorimeter,
and use that data obtained to
calculate the enthalpy change for a
reaction.
Solve numerical problems related to
thermo chemical equation.
3. Calorimetry Lab: The heat of
solution of ammonium nitrate.
[1 hr]
Demonstrate an experiment in the lab
using solution of ammonium nitrate
NH4No3
By the end of the lesson students will
be able to ;
Compare the actual heat of reaction
to the theoretical value
D2, D2.4
4. Hess’s law
D2, D3, D3.4
[3 hrs]
Explain principle of Hess’s law and
how it is applied to find the enthalpy
changes of a reaction by giving
examples of oxidation of nitrogen to
produce nitrogen dioxide.
N2 (g) +2O2 (g) --- 2NO2 (g)
Where H = 68 KJ
Solve numerical problems related to
energy changes in a chemical reaction,
using Hess’s law.
Explain Hess’s law using real life
examples like fire walking.
By the end of the lesson students will
L=Classroom Laboratory
(Link “Lab 3” at end of
document, the solid is not
indicated in the lab
procedure, but ammonium
nitrate should be used).
E = Level 1-4 rubric
attached to
laboratory.
Assessing all 4
categories: K/U, A,
T/I, C.
A=Completed laboratory
report from link, including
“Advance Study
Assignment” page 4-5.
One question to be added
– Propose possible sources
of error.
L= Lecture, problem
solving, discussion
E= numerical
problem
A= Numerical problem
E1=excellent, A=
good, B= fair, C= not
understood
be able to ;
Calculate change in enthalpy (H) of a
chemical reaction.
Understand characteristics of enthalpy
Able to distinguish endothermic and
exothermic reaction.
Better understand the heat flow
between reactant and product
How to use Hess law in solving
numerical problem
5. Testing Hess’s Law
D2.6
[1hr]
Online Java Simulation. Measure heats
of reaction from the combustion of
magnesium, and combine them to
yield the ΔH value of the reaction.
6. Problems on enthalpy, Gibbs free
energy, entropy
[3hrs]
Solve numerical problems based on
enthalpy
Explain and derive the equation based
on gibbs free energy and then solve
problems involving the Gibbs
equation, ΔG = ΔH – TΔS
By the end of the lesson students will
be;
Able to explain relation between
Gibbs free energy, entropy and
enthalpy and would be able to solve
problems based on it.
D2, D2.7, D3.3
L = Online Simulation (See
“Lab 5” link at end of
document),
E = Level 1-4 rubric
attached to
laboratory.
A = Completed enthalpy
diagram and ΔH value of
the reaction.
Assessing A & T/I.
L= Problem solving,
question and answer
E= Objective test,
A= Numerical problem
E1=excellent, A=
good, B= fair, C= not
understood
7.Rates of reaction
D3, D3.2
[2 hrs]
Describe rate of reaction which states
that, “how quickly reactants are used
up or how quickly products are
formed during a chemical reaction.”
The units used are: (moles/second)
Factor effecting rates of reaction and
explain endothermic and exothermic
reaction.
L= Lecture,
experimentation,
demonstration
A= Short essay
By the end of the lesson students will
be;
Measuring rate of reaction in the lab
8. Potential energy diagrams and
collision theory
By the end of the lesson, students will
be able to describe simple potential
energy diagrams of chemical
reactions, including relationships
between the relative energies of
reactants and products and the
activation energy of the reaction. Also
students can explain collision theory
and its relationship to chemical
reactions.
[2 hrs]
D3.5, D3.6
9. Collision Theory Gizmo
D2.8, D3.5
[2 hrs]
Online simulation to determine how
various factors (e.g., change in
temperature, addition of a catalyst,
L= Lecture & class
discussion on potential
energy diagrams. Student
activity on collision theory:
Molecule speed dating!
How do molecules meet
and interact, an interactive
simulation of collision
theory on the macro level.
E = Marking scheme
for potential energy
diagrams.
Assessing KU and C
in potential energy
diagrams, and I/T
for simulation of
collision theory.
A= Draw potential energy
diagrams, labeled with
calculations.
L=Online Gizmo Simulation
(Link “Lab 9” at end of
document).
E = Level 1-4 rubric
attached to student
exploration guide.
A=Completed Student
Assessing K/U & C.
increase in surface area of a solid
reactant) affect the rate of a chemical
reaction
10. Controlled reactions
By the end of the lesson, student will
be able to explain, with reference to a
simple chemical reaction (e.g.,
combustion), how the rate of a
reaction is determined by the series of
elementary steps that make up the
overall reaction mechanism.
[1 hr]
Exploration Guide from
website. Note: This is a
long Gizmo. Prior
Knowledge Questions can
be discussed in previous
lesson, but Gizmo is
allotted 2 periods for
completion.
D3.7
L= Graffiti Wall: students
walk around to stations
with poster paper and
circle intermediates in a
series of chemical
equations. In the final
rotation students write the
overall chemical reaction.
Completed with class
discussion on the
importance of
intermediates and how
they help us find the rate
of reaction.
Assessing A, C & T/I.
A= Students post their
corrected poster papers
from the Graffiti Walk.
11. Unit Test Review
All expectations
Prepared multiple-choice
clicker presentation.
Clicker questions should
take 20-25 mins, followed
by students working in
pairs to focus on incorrect
answers.
E = report from
clicker software on
incorrect answers.
12. Unit Test
Lab 3: http://sunny.moorparkcollege.edu/~chemistry/chemistry_1B_labs/experiment_one.pdf
Lab 5: http://www.dartmouth.edu/~chemlab/info/resources/deltah/deltah.html
Lab 9: http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=553
Accommodations for (ELL) English language learners
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Access to dictionary
Use visuals/ manipulative
Teach key vocabulary
Adjust speech
Utilize cooperative learning methods
Use coping strategies
Give them extra time
Make activities more simple
Provide native language instruction and materials
Provide “think aloud” and modeling
Set language, content, and learning-strategy objectives
Tap students’ prior knowledge.
Scaffolding of tasks
Accommodations for students with IEPs
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Increase the variety of information available
Use assignments according to student readiness
Do not explore related ethical issues
Give them extra time
Tap students’ prior knowledge
Utilize cooperative learning methods
Use coping strategies
Scaffolding of tasks
Give them extra time
Access to dictionary
Be sympathetic and accommodating to his needs.
Make activities more simple
Accelerate activities from concrete to abstract, move slowly
Modify outcomes from a lower grade level
Do not extend activities beyond the regular program of studies
For laboratories keep groups consistent to avoid stress caused by change
REFERENCES:
Ontario curriculum for senior science
http://schools.hwdsb.on.ca/westdale/files/2010/10/Grades-11-and-1210.pdf
Growing success- Assessment, Evaluation, and Reporting in Ontario schools
http://www.edu.gov.on.ca/eng/policyfunding/growSuccess.pdf
Culminating Task
SCH4U Strand D: Energy Changes and Rates of Reactions
(Submitted by Vanessa Poehlmann, Amarinder Sawhney, Rajni Kant Sharma)
Background Information
The foundation of the study of thermochemistry is Hess’s Law which states :
The enthalpy change for any reaction depends on the products and the reactants and is
independent of the pathway or the number of steps between the reactant and product.
This task is divided into two parts
Part A tests students KIU part of assessment tools and Part B tests A part of evaluation tools.
Part A is group task involving 2 or 3 students in one group and Part B is individual task.
Part A Energy changes- Applications of Hess’s law in lab
In this experiment, you will measure and compare the quantity of heat involved in the following
three reactions. Half of class will choose reaction 1 and other half will choose reaction 2.
Reaction 3 will be performed by every group. Students will share readings of 1 and 2 and will
solve equation3
Neutralisation reaction between HCl and NaOH
1. The dissolving of solid sodium hydroxide in water:
NaOH(s)
Na+(aq) + OH-(aq) + heat
2. The reaction of solid sodium hydroxide and dilute hydrochloric acid:
NaOH(s) + H+(aq) + Cl-(aq)
Na+(aq) + Cl-(aq) + H2O(l) + heat
3. The reaction of sodium hydroxide solution with dilute hydrochloric acid:
Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq)
Na+(aq) + Cl-(aq) + H2O(l) + heat
Objective: To measure and compare the amounts of heat involved in three separate but
related reactions to provide experimental verification of Hess’s Law.
Materials:
Thermometer
Styrofoam cup
Solid NaOH
0.50M NaOH(aq)
0.25 M HCl(aq)
0.50 M HCl(aq)
Reaction One: The Dissolving of Solid Sodium Hydroxide in Water
Put 200 mL of distilled water into the styrofoam cup. Measure and record the
temperature.
Record the mass of approximately 2.00g solid sodium hydroxide. Transfer it into the water
in the styrofoam cup. DO NOT TOUCH THE SOLID SODIUM HYDROXIDE WITH YOUR HANDS.
Stir gently with the thermometer until the solid is completely dissolved and record the
highest temperature reached.
Discard the solution in the disposal beaker on the front bench and rinse the cup
thoroughly with tap water.
Reaction Two: The Reaction of Solid Sodium Hydroxide with Hydrochloric Acid Solution
Put 200 mL of .25m HCl into the styrofoam cup. Measure and record the temperature.
Record the mass of approximately 2.00g solid sodium hydroxide. Transfer it into the .25M
hcl in the styrofoam cup. Stir gently with the thermometer until the solid is completely
dissolved and record the highest temperature reached.
Discard the solution in the disposal beaker on the front bench and rinse the cup
thoroughly with tap water.
Reaction Three: The Reaction of Sodium Hydroxide Solution with Hydrochloric Acid Solution
Accurately measure 100 mL of 0.50 M HCl into the styrofoam cup and 100 mL of 0.50 M
NaOH into a 250 mL beaker. Record the temperatures and volumes of each solution.
Add the NaOH solution to the HCl solution in the cup. Stir the mixture with the
thermometer and record the highest temperature reached.
Discard the solution down the sink, and rinse both containers well.
Calculations: From your data, calculate the following for each part of the experiment:
The temperature change of the liquid (Δt).
The heat absorbed by the solution (Q = mcΔt: assuming that the specific heat capacity of
the solution is approximately equal to that of water and that the density of the solutions are
equal to that of pure water).
The number of moles of sodium hydroxide present.
Write a report highlighting these three questions :
1. Add the ionic equations given for part one and part three. Compare the result with the
ionic equation for part two.
2. Compare the sum of the heats of reaction for parts one and three with that obtained for
part two. In light of your answer to question #2, explain your results here.
3. Discuss Hess's Law in terms of the Law of Conservation of Energy and in terms of the three
parts of this experiment.
Data entry tables for calculation
1.NaOH(s)
NaOH(aq)
Mass of NaoH
taken(g)
Initial temp of
water
2.NaOH(s)+HCl(aq)
Mass of NaOH(g)
ΔT
ΔH for reaction A
NaCl(aq)+ H2O(l)
Initial temp of HCl
3.NaOH(aq)+HCl(aq)
Initial Temp of Hcl
Final temp of
solution
Final temp of
solution
ΔT
ΔH for reaction B
NaCl(aq)+ H2O(l)
Final temp of
solution
ΔT sol
ΔH for reaction C
Calculate ΔH for all three reactions and prove Hess’s law
Part B : Application of rates of reaction and factors affecting rates of reactions
Write a report on practical application of day to day life featuring effect of temperature, catalysts,
concentration on rates of reactions. Explain how your application makes an impact on society and
technology in the real world.
Or
Give a power point presentation on rates of reactions and factors affecting them illustrating practical
examples. Explain how your examples make an impact on society and technology in the real world.
Here are just a few everyday demonstrations that temperature changes the rate of chemical reaction:
Cookies bake faster at higher temperatures.
Bread dough rises more quickly in a warm place than in a cool one.
Low body temperatures slow down metabolism. In fact, warm-blooded animals regulate body
temperature so that their biochemical reactions run at the correct rate. (Homeostasis)
Growth of micro organisms stop at low temperature
Washing of clothes at optimum temperature
Increasing the concentration of reactants also changes reaction rate:
Two antacid tablets will neutralize a given amount of acid faster than one tablet will. Higher con
centrations of acid in rain erode marble faster than lower concentrations.
General instructions and precautions
Record your instructions once you complete experiment
Spillage of chemicals/reagents should be cleaned immediately and safely
Always maintain cleanliness at your work station
Wash and handle apparatus(glassware ) carefully
After finishing your experiment, turn off instrument used
Avoid wastage of water
Maintain good lab practice
In case of swallowing of a chemical, tell lab in charge immediately
Always wear proper PPE in lab
No eatables allowed in lab
No loose clothes or open hair in lab
Resources for Part A
http://www.instruction.greenriver.edu/kmarr/Chem%20161/Chem%20161%20Labs/Lab%209
%20Hess's%20Law/Lab%209_Hess's%20Law_Vernier_Report%20Sheet_F2009.pdf
http://www.wiziq.com/tutorial/179525-Chemistry-Laboratory-Manual
For ELL students
http://www.youtube.com/watch?v=8yFjgAtB8yg
Resources for Part B
http://www.scienceclarified.com/everyday/Real-Life-Chemistry-Vol-1/Temperature-and-Heat-Reallife-applications.html
For ELL students http://www.youtube.com/watch?v=izqJkdj1d4U
http://www.slideshare.net/Emersius/rate-of-reactions
Discrepant event on rates of reaction
http://www.nipissingu.ca/education/geraldl/sciencegeneral/discrepant_events
.htm
Assessment tools for Culminating Task
1.Peer evaluation: This evaluation will be done by students and every student
will mention 3 names of students and will rate on these traits worth 5 points
each. Top 3 students will get peer recognition award.
Name
Responsibility organisation Independent collabration initiative
of
work
student
2.Rubric chart: for assessment by teacher
NOTE: Part A & B are both assessed for KICA, look under first column to see which part is assessed for
each item.
Knowledge and
Understanding
Level 1 (50-59%)
Level 2 (60-69%)
Level 3 (70-79%)
Level 4: (80-100%)
Part A: Knowledge of
content of energy and
rates of reaction
(e.g., facts, terminology,
definitions, numerical, lab
work, etc.)
demonstrates
limited knowledge
of
content
demonstrates some
knowledge of
content
demonstrates
considerable
knowledge of
content
Demonstrates a
high degree of
knowledge of
of content
Part B: Can summarize
topic and do research)
(e.g., concepts, ideas,
theories, procedures,
processes etc.)
demonstrates
limited summary
and research of the
into the topic
demonstrates some
summary and
research of the into
the topic
demonstrates
considerable
summary and
research of the into
the topic
demonstrates
a high degree of
summary and
research of the into
the topic
Inquiry
Part A: Use of initiating
and planning skills and
strategies
(e.g., formulating
questions, identifying the
problem, developing
hypotheses,
scheduling, selecting
strategies and resources,
developing plans)
Part B: Use of
critical/creative
thinking processes,
skills, and strategies
(e.g., analysing,
interpreting,
problem solving,
evaluating,
forming and researching)
Communication
Part A & Part B:
Expression and
organization of ideas
and information
in oral, visual, and/or
written forms ( clear
expression, logical
organization in diagrams,
models)
Part B: Communication
to audience with the
purpose of informing
them oral, visual, or
written forms.
Part A & Part B: Use of
conventions,
vocabulary, and
terminology of the
discipline in oral, visual,
and/or written forms
( e.g. Symbols, formula,
scientific notation,
chemical reactions etc.)
Application
Part A: Application of
knowledge and skills
(e.g., concepts and
Level 1 (50-59%)
Level 2 (60-69%)
Level 3 (70-79%)
Level 4: (80-100%)
Completion of
Hess’ Law
experiment uses
initiating
and planning
skills and
strategies
with limited
effectiveness
Completion of
Hess’ Law
experiment uses
initiating
and planning
skills and
strategies
with some
effectiveness
Completion of
Hess’ Law
experiment uses
initiating
and planning
skills and
strategies
with considerable
effectiveness
Completion of
Hess’ Law
experiment uses
initiating
and planning
skills and
strategies
with a high degree
of effectiveness
Research into topic
shows
critical/creative
thinking
processes, and
connections to rates
of reaction are
made with limited
effectiveness.
Research into topic
shows
critical/creative
thinking
processes, and
connections to rates
of reaction are
made with some
effectiveness.
Research into topic
shows
critical/creative
thinking
processes, and
connections to rates
of reaction are
made with
considerable
effectiveness
Research into topic
shows
critical/creative
thinking
processes, and
connections to rates
of reaction are
made with a high
degree of
effectiveness.
Level 1 (50-59%)
Level 2 (60-69%)
Level 3 (70-79%)
Level 4: (80-100%)
expresses and
organizes ideas
and information
with limited
effectiveness
expresses and
organizes ideas
and information
with some
effectiveness
expresses and
organizes ideas
and information
with considerable
effectiveness
expresses and
organizes ideas
and information
with a high degree
of effectiveness
Presentation of
material in
student’s choice of
delivery method
(report,
presentation, etc.)
was limited in
clarity, logic &
information to
viewers.
uses conventions,
vocabulary, and
terminology of the
discipline with
limited
effectiveness
Presentation of
material in
student’s choice of
delivery method
(report, presentation
etc.) had some
clarity, logic &
information to
viewers.
Presentation of
material in
student’s choice of
delivery method
(report, presentation
etc.) had
considerable clarity,
logic & information
to viewers.
Presentation of
material in
student’s choice of
delivery method
(report, presentation
etc.) had a high
degree of clarity,
logic & information
to viewers.
uses conventions,
vocabulary, and
terminology of the
discipline with
some
effectiveness
uses conventions,
vocabulary, and
terminology of the
discipline with
considerable
effectiveness
uses conventions,
vocabulary, and
terminology of the
discipline with
a high degree of
effectiveness
Level 1 (50-59%)
Level 2 (60-69%)
Level 3 (70-79%)
Completion of
Hess’ Law
experiment shows
Completion of
Hess’ Law
experiment shows
Completion of
Hess’ Law
experiment shows
Level 4: (80-100%)
Completion of
Hess’ Law
experiment shows
processes,
safe use of equipment
and technology
,investigation
skills) in familiar
contexts
Part B: Transfer of
knowledge
and skills (e.g., concepts
and processes, safe use of
equipment and
technology,
investigation skills) to
real life problems
Part B: Made
connections between
science, technology,
society, and the
environment, and
proposed of practical
action to
deal with problems
relating to science,
technology, society,
and the environment.
that knowledge
and skills are
applied in familiar
contexts
with limited
effectiveness.
Transfer knowledge
and skills of
chemical reactions
to solve real-life
problems with
limited of
effectiveness
that knowledge
and skills are
applied in
familiar contexts
with some
effectiveness
Transfer knowledge
and skills of
chemical reactions
to solve real-life
problems with
some of
effectiveness
that knowledge
and skills are
applied in
familiar contexts
with considerable
effectiveness
Transfer knowledge
and skills of
chemical reactions
to solve real-life
problems with
considerable
effectiveness
that knowledge
and skills are
applied in
familiar contexts
with a high degree
of effectiveness
Transfer knowledge
and skills of
chemical reactions
to solve real-life
problems with a
high degree of
effectiveness
Related to their
research topic,
student makes
connections to
technology and
society with limited
effectiveness
Related to their
research topic,
student makes
connections to
technology and
society with some
effectiveness
Related to their
research topic,
student makes
connections to
technology and
society with
considerable
effectiveness
Related to their
research topic,
student makes
connections to
technology and
society with a high
degree of
effectiveness
Resource for assessment tool
http://www.edu.gov.on.ca/eng/policyfunding/growSuccess.pdf
NAME: _______________________________
DATE: _____________________________
Unit Test – Energy Changes and Rates of Reaction
Part A: Multiple Choice – Circle the correct answer

[
/5 K]
The same reaction was carried out at four different temperatures and the times taken for the
reaction recorded.
Temperature [o C]
Time [s]
20
60
30
30
40
14
50
5
The results show that:
 A small rise in temperature results in a large increase in reaction rate
 The activation energy increases with increasing temperature
 The rate of the reaction is directly proportional to the temperature
 The reaction is endothermic

Which of the following is not a correct statement about the effect of a catalyst?
A catalyst:
 Lowers the energy which molecules need for successful collision
 Provides an alternative route to the products
 Forms weak bonds with reacting molecules
 provides energy so that more molecules have successful collisions

The standard Gibbs free energy of formation of __________ is zero.








3. H2 (g)
(1) only
(2) only
(3) only
(2) and (3)
(1), (2), and (3)
the residual energy present in the reactants at equilibrium
the residual energy present in the products at equilibrium
the difference in the residual energy of reactants and products at equilibrium
the difference in the residual energy of reactants and products at equilibrium
In a gas phase reaction, what is the effect of increasing reactant or product pressure on the
standard Gibbs free energy?





It increases due to decreased entropy
It decreases due to decreased entropy
It increases due to increased enthalpy
It may either increase or decrease
It is unchanged
Part B: Short Answer

2. O (g)
The Standard Gibb's free energy, ΔG°, is:




H2O (l)
[
/6 K]
In terms of reaction kinetics, explain why each of the following speeds up a chemical
reaction. [ 3 MARKS K]
 Catalyst



Increase in temperature
Increase in concentration
Answer questions (a)-(c) based on the potential energy diagram below. [ 3 MARKS K]

Which letter depicts the potential energy of the activated complex?

Which letter depicts the activation energy of the reverse or backward reaction? _______

What is the value for the Ear?
Part C: Long Answer

_______
_______
[
/6A]
Consider the following equilibrium:
N2(g) + 3H2 (g)
2NH3(g)
The reaction is exothermic with 22kcal of heat produced.

What is the effect of adding more nitrogen to the system, observed in a vessel at constant
volume?
 What is the effect of an increase in temperature on the equilibrium, at constant pressure?
 What is the effect on the equilibrium if the volume is halved, thus initially doubling the
total pressure?
Make reference to Le Chatelier’s Principle in your responses.
Part D: Problem Solving

[
/20A]
At a temperature of 350oC, the equilibrium concentrations for the reaction:
N2(g) + 3 H2 2 NH3(g)
are:
[N2] = .885, [H2] = .665, [NH23] = 1.230
Calculate the value of the equilibrium constant for the reaction at 350 degree Celsius.

When one mole of sulfur burns to form SO2, 1300 calories are released. When one mole of
sulfur burns to form SO3, 3600 calories are released. What is the ΔH when one mole of
SO2 is burned to form SO3? [ 6 MARKS A]

For the reaction:
Fe2O3 (s) + 3 CO (g) → 2 Fe (s) + 3 CO2 (s)
ΔG° = -31.3 kJ.
Calculate the standard free energy of formation of the ferric oxide, Fe2O3, given:
ΔG°f of CO = -137 kJ/mol, and
ΔG°f of CO2 = -394 kJ/mol.
[ 6 MARKS A]

(a) Calculate ΔG at 25°C for the following reaction, by first calculating ΔH and ΔS.
(b) Once you've found ΔH and ΔS, solve for ΔG using the formula:
ΔG = ΔH - T ΔS
(c) Will this reaction be spontaneous at this temperature?
CH3CO2H (l) + 2 O2 (g) → 2 CO2 (g) + 2 H2O (g)
Values Given according to table;
For CH3CO2H, ΔH = -484.5 and ΔS =159.8
For CO2, ΔH = -393.5 and ΔS =213.7
For H2O, ΔH = -241.8 and ΔS =188.8
For O2, ΔH = 0 and ΔS =205.1
[ 8 MARKS A]
Answer Key – Energy Changes and Rates of Reaction Unit Test
Multiple Choice
1) a
2) d
3) c
4) d
5) a
Short Answer
6)

A catalyst lowers the activation energy, therefore more molecules in the sample
have sufficient energy to reach
 A temperature increase causes a greater fraction of the molecules to have an energy
at least equal to the activation energy
 A concentration increase causes a greater number of collisions per second, therefore
a greater number of effective collisions.
7) a) B b) E c) 50 KJ- 10 KJ= 40 KJ/mol
Long Answer:
8)

If nitrogen is added to the system, equilibrium will shift to the right to use up some of
that nitrogen. Le Chatelier’s principle does not tell us exactly how much the equilibrium
is shifted, but some hydrogen gas will be present at the new equilibrium state, no matter
how much nitrogen is added.

In the application of Le Chatelier’s principle, the heat produced may be treated as one of
the products of this exothermic reaction
N2(g) + 3H2 (g)
2NH3(g) + 22kcal
An increase in temperature means that heat was added to the equilibrium. Therefore to
use up some of that excess heat, equilibrium will shift to the left.
c) The reactants in this equilibrium total 4 moles, and the products total 2 moles. If the total
pressure is doubled, equilibrium will shift to the right. Fewer moles of gas will exert less
pressure, as stated by Le Chatelier’s principle.
Problem Solving
9) Keq = [NH3]2
[N2][H2]3
substitute known values in above formula
Keq= [1.230]2
[.885] [.665]3
=5.8130226
=5.81
10)





Writing out the chemical equations:
S + O2 ---> SO2
ΔH = -1.3 kcal
S + (3/2)O2 ---> SO3
ΔH = -3.6 kcal
The target equation is:
SO2 + (1/2) O2 ---> SO3
To obtain the target equation we have to flip the first equation and sign on the enthalpy
will change. Equations with the first one flipped:
SO2 ---> S + O2
ΔH = +1.3 kcal
S + (3/2)O2 ---> SO3
ΔH = -3.6 kcal
After adding two equations , the S and an O2 will cancel out:
SO2 + (1/2) O2 ---> SO3
After adding the enthalpies:
+1.3 + (-3.6) = -2.3 kcal or -2300 cal
12)
Value of ΔG° is given, and need to find ΔG°f for one of the reaction participants, Fe2O3. Let's
value of unknown equal x:
Fe2O3
+
3 CO
→
2 Fe
+
3 CO2
x
+
3(-137)
2(0)
+
3 (-394)
- 411
-1182
After substituting the values in the following formula;
ΔG
= ΣΔG° products - ΣΔG° reactants
-31.3
= (-1182) - (x - 411)
-31.3
= -1182 - x + 411
-31.3
= -771-x
x
= -771 + 31.3
x
= -740
Therefore ΔG°f for Fe2O3 = -740 kJ/mol
12)

Step 1 - Calculate ΔH
CH3CO2H
-484.5
+
+
2 O2
2 (0)
-484.5
→ 2 CO2
2 (-393.5)
+ 2 H2O
+ 2(-241.8)
-1270.6
ΔH
ΔH
Step 2- Calculate ΔS
CH3CO2H
159.8
570.0
= ΣΔH° products - ΣΔH° reactants
= -1270.6 - (-484.5)
= -786.1 kJ
+
+
2 O2
2(205.1)
→
2 CO2
2(213.7)
+
+
2 H2O
2(188.8)
805.0
ΔS
= ΣΔS° products - ΣΔS° reactants
= 805.0 - (570.0)
ΔS
= 235.0 J/K = 0.235 kJ/K
Step 3 - Calculate ΔG Be sure to convert 25°C into K and ΔS into kJ/K
K
= C + 273
= 25 + 273
K
= 298 K
ΔG
= ΔH - T ΔS
= -786.1 - 298.0(0.235)
ΔG
= -856.1 kJ
Because ΔG is negative, the reaction is spontaneous at this temperature.