CHEM 203 Lab 2: Kinetics of the Iodine Clock Reaction Winter 2025
grade
Lab 2: Kinetics of the Iodine Clock Reaction
By completing all parts of this lab, you will collect data on the rate of the iodine clock reaction
with varying initial reactant concentrations to determine the rate law for this reaction.
You will work and discuss in pairs for this lab, Before your lab...
BUT you will individually submit a completed 1. Read briefly through…
report. Lab 2 (this document)
Complete your lab Worksheet at home within 2. Complete…
one week after your lab session. Upload the Pre-lab 2 (D2L quiz), with a score of
Worksheet file (as a PDF) to Gradescope by 50% or higher
the starting time of your lab section. Questions P1 and P2 in this
document – Page 10. You will need
these ideas and values in the lab, so
What laboratory techniques and skills will you come prepared! The pre-lab quiz is
practice? closely related and will help.
Collecting data in a timed experiment All parts of Lab 0, if you haven’t yet
Preparing solutions in volumetric
glassware You will not be allowed to
enter the lab if Lab 0 is
Conducting experiments at a microscale
incomplete or you have not
passed the Lab 2 pre-lab quiz.
What chemical concepts will you apply? Contact your TA or lab
coordinator if you have
Concentration & dilution
issues with either task.
Relative rates of reaction
UCalgary Chemistry Textbook: If concepts are unclear or new, refer to the
7.1.3 - Relative Rates of Reaction course textbook to review them.
OpenStax 2e
12.1 - Relative Rates of Reaction On your lab day...
Using the method of initial rates to Wear clothes & footwear that covers
determine rate laws any exposed skin below the hem of
UCalgary Chemistry Textbook: the lab coat, including your ankles.
7.3.3 - Method of Initial Rates Bring your lab coat & safety glasses
OpenStax 2e Bring printed copies of...
12.3 - Rate Laws Lab 2
Lab Appendix G
What communication and reporting skills will
Bring a pen (not pencil) and scientific
you use? calculator
Recording data and observations Arrive at least 5-minutes early
Presenting data and results in tables
Describing assumptions and uncertainty in
experimental design
Lab 2: Background Do Not Scan Me to Gradescope Page 1
, CHEM 203 Lab 2: Kinetics of the Iodine Clock Reaction Winter 2025
Key Safety Information
Hydrochloric acid (HCℓ) solutions are corrosive at 6 M concentrations.
We are handling it with care and only in small quantities. Wash your
hands immediately if your skin comes in contact with the solution. At
this concentration, it can also give off vapours that act as respiratory or
Corrosive Irritant
eye irritants, so it should be handled strictly in the fumehood.
Always add acids to water when preparing or diluting solutions – this
process is exothermic and can result in dangerous splashing water is
added directly to concentrated acids.
Hydrogen peroxide (H2O2) can cause short-term (acute) aquatic
toxicity, depending on concentration. Follow appropriate disposal
procedures.
Aquatic Irritant
Potassium iodide (KI) can cause serious eye irritation. Avoid contact
toxicity
with eyes.
ADDITIONAL SAFETY NOTES FOR SAFE HANDLING & DISPOSAL ARE EMBEDDED AT THE RELEVANT POINTS IN THE PROCEDURE.
Background
Describing the reactions for the iodine clock and corresponding rate laws
In this experiment, you will study a series of reactions commonly known as an “iodine clock,” named
because we can track the time it takes to produce a certain amount of iodine, I2.¹
The primary reaction we will study is shown in reaction [1], below.
2 H+ (aq) + 2 I⁻ (aq) + H2O2 (aq) → I2 (aq) + 2 H2O (ℓ) [1]
This reaction is relatively ‘slow’ in kinetic terms, so it can be readily studied with a stopwatch. Our
goal in this experiment is to determine the rate law for this primary reaction, which we can write
generally as,
𝑅𝑎𝑡𝑒 = 𝑘[𝐻+]𝑎[𝐼−]𝑏[𝐻2𝑂2]𝑐 [2]
The rate law in this form will allow us to express how much a change in the concentrations of each of
our reactants impacts the rate or speed of the reaction.
As you have learned in-class, reactions like this one often happen in several mechanistic steps before
arriving at this overall reaction. Since we do not know the mechanism here, we must determine the
rate law experimentally. To do so, we need to be able to observe or measure how quickly our
Lab 2: Background & Procedures Do Not Scan Me to Gradescope Page 2
grade
Lab 2: Kinetics of the Iodine Clock Reaction
By completing all parts of this lab, you will collect data on the rate of the iodine clock reaction
with varying initial reactant concentrations to determine the rate law for this reaction.
You will work and discuss in pairs for this lab, Before your lab...
BUT you will individually submit a completed 1. Read briefly through…
report. Lab 2 (this document)
Complete your lab Worksheet at home within 2. Complete…
one week after your lab session. Upload the Pre-lab 2 (D2L quiz), with a score of
Worksheet file (as a PDF) to Gradescope by 50% or higher
the starting time of your lab section. Questions P1 and P2 in this
document – Page 10. You will need
these ideas and values in the lab, so
What laboratory techniques and skills will you come prepared! The pre-lab quiz is
practice? closely related and will help.
Collecting data in a timed experiment All parts of Lab 0, if you haven’t yet
Preparing solutions in volumetric
glassware You will not be allowed to
enter the lab if Lab 0 is
Conducting experiments at a microscale
incomplete or you have not
passed the Lab 2 pre-lab quiz.
What chemical concepts will you apply? Contact your TA or lab
coordinator if you have
Concentration & dilution
issues with either task.
Relative rates of reaction
UCalgary Chemistry Textbook: If concepts are unclear or new, refer to the
7.1.3 - Relative Rates of Reaction course textbook to review them.
OpenStax 2e
12.1 - Relative Rates of Reaction On your lab day...
Using the method of initial rates to Wear clothes & footwear that covers
determine rate laws any exposed skin below the hem of
UCalgary Chemistry Textbook: the lab coat, including your ankles.
7.3.3 - Method of Initial Rates Bring your lab coat & safety glasses
OpenStax 2e Bring printed copies of...
12.3 - Rate Laws Lab 2
Lab Appendix G
What communication and reporting skills will
Bring a pen (not pencil) and scientific
you use? calculator
Recording data and observations Arrive at least 5-minutes early
Presenting data and results in tables
Describing assumptions and uncertainty in
experimental design
Lab 2: Background Do Not Scan Me to Gradescope Page 1
, CHEM 203 Lab 2: Kinetics of the Iodine Clock Reaction Winter 2025
Key Safety Information
Hydrochloric acid (HCℓ) solutions are corrosive at 6 M concentrations.
We are handling it with care and only in small quantities. Wash your
hands immediately if your skin comes in contact with the solution. At
this concentration, it can also give off vapours that act as respiratory or
Corrosive Irritant
eye irritants, so it should be handled strictly in the fumehood.
Always add acids to water when preparing or diluting solutions – this
process is exothermic and can result in dangerous splashing water is
added directly to concentrated acids.
Hydrogen peroxide (H2O2) can cause short-term (acute) aquatic
toxicity, depending on concentration. Follow appropriate disposal
procedures.
Aquatic Irritant
Potassium iodide (KI) can cause serious eye irritation. Avoid contact
toxicity
with eyes.
ADDITIONAL SAFETY NOTES FOR SAFE HANDLING & DISPOSAL ARE EMBEDDED AT THE RELEVANT POINTS IN THE PROCEDURE.
Background
Describing the reactions for the iodine clock and corresponding rate laws
In this experiment, you will study a series of reactions commonly known as an “iodine clock,” named
because we can track the time it takes to produce a certain amount of iodine, I2.¹
The primary reaction we will study is shown in reaction [1], below.
2 H+ (aq) + 2 I⁻ (aq) + H2O2 (aq) → I2 (aq) + 2 H2O (ℓ) [1]
This reaction is relatively ‘slow’ in kinetic terms, so it can be readily studied with a stopwatch. Our
goal in this experiment is to determine the rate law for this primary reaction, which we can write
generally as,
𝑅𝑎𝑡𝑒 = 𝑘[𝐻+]𝑎[𝐼−]𝑏[𝐻2𝑂2]𝑐 [2]
The rate law in this form will allow us to express how much a change in the concentrations of each of
our reactants impacts the rate or speed of the reaction.
As you have learned in-class, reactions like this one often happen in several mechanistic steps before
arriving at this overall reaction. Since we do not know the mechanism here, we must determine the
rate law experimentally. To do so, we need to be able to observe or measure how quickly our
Lab 2: Background & Procedures Do Not Scan Me to Gradescope Page 2
