kinetic the clock reaction
Here’savideo showing what you see in lab:
[+]
The data we take is simply the time until we see the color change. The time is influenced strongly by consistent stirring and the timing of the stopwatch turning on/off. After you complete the pre-lab quiz online, you will get access to data to use in your notebook for the post-lab work.
Here’s a video overview of the lab:
[+]
upload your calculations (work) for the table of Molar Concentrations after mixing the solutions.
CHEM 121: Kinetics: The Clock Reaction
Introduction
The iodine “clock reaction” is a reaction famous for its dramatic clear-to-blue color
change, often used in introductory chemistry courses to explore the speed at which
reactions occur—that is, the “kinetics” of a reaction.
The clock reaction is actually three reactions which occur in sequence:
(1)
IO3-(aq) + 3 HSO3-(aq) ® I-(aq) + 3 SO42-(aq) + 3 H+(aq)
(2)
IO3-(aq) + 5 I-(aq) + 6 H+(aq) ® 3 I2(aq) + 3 H2O(l)
(3)
I2(aq) + starch ® {a dark blue iodine-starch complex}
The focus of this experiment is not to understand how all three steps of the overall
reaction work together but to recognize that if aqueous solutions of iodate ion (IO3-)
and bisulfite ion (HSO3-) are mixed, a series of reactions will occur to produce
iodine (I2), and the final reaction is signaled by the appearance of the dark blue
color of the iodine-starch complex. Note that I2 has an amber color when dissolved
in water, so its presence is harder to detect by itself. The starch serves as an
indicator to help us “see” the I2 more easily since the two together form a dark blue
complex.
The time required for the dark blue color to appear (i.e., for the I2 to form) is related
to the rate of the reaction. The shorter the reaction time until the color appears, the
faster the reaction; the longer the reaction time, the slower the reaction.
For this lab, you will investigate how the concentration of the reactants and
temperature affect the rate of this reaction. This experiment will also provide
experience in solution preparation and dilution.
Procedure
Before starting, wash thoroughly, do a final rinse with DI water, and dry all the
required glassware for this experiment because trace contaminants can
significantly affect your results in these reactions. Use acetone in the hood to
rinse the inside of wet test tubes, graduated cylinders, and flasks, so they will
dry faster. Pour any excess acetone into the labeled waste container in the
hood.
PART I: Solution preparation
A. Prepare 100.0 mL of a 0.0200M sodium bisulfite solution in water.
1. Write the formula of sodium bisulfite in your Lab Report form.
2. Calculate the mass of solid sodium bisulfite required to prepare 100.0 mL of
a 0.0200M sodium bisulfite solution in water, and record the mass in your
Data Table under Calculated.
CHEM 121 Lab Manual F2019
page 97
3. Use the analytical balance to weigh out close to the calculated mass of
sodium bisulfite, and record the actual amount used. It does not have to be
exactly the mass you calculated but should be close to it. Transfer the solid
to an empty 100.0 mL volumetric flask.
4. Add about 50 mL of deionized water to the flask, and swirl the solution
until the solid has dissolved completely.
5. Carefully add enough water to bring the volume right to the “mark” on the
neck of the flask. Use a disposable pipet to add the last few drops to get the
volume right at the mark! If you add too much DI water
6. Pour this solution into a dry 125-mL Erlenmeyer flask, and label it
“0.0200M sodium bisulfite”.
B. Prepare 100.0 mL of 0.0200M potassium iodate solution by diluting a 0.100M
potassium iodate solution.
1. Write the formula for potassium iodate in your Lab Report form.
2. Use M1V1=M2V2 to calculate the volume of the original 0.100 M potassium
iodate solution required to prepare 100.0 mL of a 0.0200M solution, then
record the calculated volume in your Lab Report.
3. Use a graduated cylinder to measure out this volume of the 0.100 M
potassium iodate solution. Pour this amount into a 250-mL Erlenmeyer
flask.
4. Calculate the amount of water which must be added to the flask to bring the
total volume to 100.0 mL. Record the volume of water to add, then add that
amount of water to the flask.
5. Label this solution “0.0200M potassium iodate”.
Part II: Measuring the Reaction Rates
A. Initial Trial of the Reaction:
1. Obtain a 10-mL graduate cylinder and label it “sodium bisulfite”. (Note:
This graduated cylinder will be used for the rest of the lab only to measuring
sodium bisulfite to avoid contamination.) Obtain a second 10-mL graduated
cylinder and label it “potassium iodate”. (Note: This second graduated
cylinder will be used only for potassium iodate to avoid contamination.)
2. Measure 10.00 mL of 0.0200M sodium bisulfite and 10.00 mL of 0.0200M
potassium iodate into the separate graduated cylinders. Add two drops of
starch to either of the solutions in the cylinders. DO NOT FORGET TO
ADD THE STARCH, OR THE COLOR CHANGE WILL NOT BE
VISIBLE. Record the volume of each reagent used in your Lab Report.
CHEM 121 Lab Manual F2019
page 98
Thoroughly clean and dry a 50-mL beaker and a glass stirring rod. Place the
50-mL beaker on a white sheet of paper on the lab countertop to observe the
color change more easily.
3. Have one person pour the two 10.00 mL solutions into the beaker and give
it a quick stir with a glass rod, while a second person starts the stopwatch.
All these things should be done at the same time.
4. When the color changes, stop the stopwatch. Convert the time to seconds,
and record the time in your Lab Report under Trial #1.
5. Use the thermometer to measure the temperature of the blue solution.
6. Thoroughly clean and dry the 50-mL beaker and the glass stirring rod
between trials.
7. Repeat steps 2-6 above for Trial #2 and Trial #3
8. Calculate the average time for trials 1-3, and record the average in your Lab
Report.
Part III: Reaction rate and concentration of reactants
A. Trial #4
1. Thoroughly clean and dry the 50-mL beaker and the glass stirring rod.
2. Repeat steps 2-5 in part II B, above. However, for potassium iodate,
measure only 8.00 mL of the 0.0200M solution into the graduated cylinder,
and then add 2.00 mL of water to bring the total to 10.00 mL. Proceed as
before.
B. Trial #5
1. Thoroughly clean and dry the 50-mL beaker and the glass stirring rod.
2. Repeat steps 2-5 in part II B, above. However, for potassium iodate,
measure only 5.00 mL of the 0.0200M solution into the graduated cylinder,
and then add 5.00 mL of water to bring the total to 10.00 mL. Proceed as
before.
C. Trial #6
1. Thoroughly clean and dry the 50-mL beaker and the glass stirring rod.
2. Repeat steps 2-5 in part II B, above. However, for sodium bisulfite, measure
only 8.00 mL of the 0.0200M solution into the graduated cylinder, and then
add 2.00 mL of water to bring the total to 10.00 mL. Proceed as before.
CHEM 121 Lab Manual F2019
page 99
D. Trial #7
1. Thoroughly clean and dry the 50-mL beaker and the glass stirring rod.
2. Repeat steps 2-5 in part II B, above. However, for sodium bisulfite, measure
only 5.00 mL of the 0.0200M solution into the graduated cylinder, and then
add 5.00 mL of water to bring the total to 10.00 mL. Proceed as before.
Part IV: Reaction rate and temperature
Using the same amounts of reactants used in part II, you will conduct the reaction
two different temperatures, to investigate the effect of temperature on reaction rate.
A. Higher Temperature
1. Pour 10.00 mL of 0.0200M sodium bisulfite into one small test tube, and
10.00 mL of 0.0200M potassium iodate and two drops of starch into a second
small test tube.
2. Put both test tubes into the warm water bath and allow them to sit for at least
5 min. (Begin part B while you’re waiting.)
3. Because the solutions will start to cool once they are removed from the
solution, this step must be done as quickly as possible. Conduct steps 3 and 4
from Part II A above to run the reaction.
4. Record the temperature of the blue solution as quickly as possible after the
color change.
B. Lower Temperature
1. Prepare an ice bath by filling your 600-mL beaker with ice, and then adding
tap water to fill it half way. Ideally, there should be enough ice to support a
beaker with the bottom of the beaker submerged in cold water.
2. Repeat steps 1-4 in part A, above, using the ice bath. Just as you did in the
warm water bath (step A2, above), you will need to cool the two solutions in
the ice bath for at least 10 minutes before running the reaction. When mixing
the two solutions in the 50-mL beaker, place the beaker gently in the ice bath
while the reaction occurs, to keep the temperature constant.
WASTE DISPOSAL: All waste for this experiment should go into the waste
containers in the hood. Wash your entire work area with a wet paper tower, then
dry. Wash your hands completely with soap and water before you leave.
CHEM 121 Lab Manual F2019
page 100
Pre-laboratory Assignment:
Do all the calculations for Part I: Solution Preparation, on the next page. Complete
everything on this page, except the “Actual amount used” in the table, which you will
record when you conduct the experiment.
Finish these calculations before your lab period, and ask your instructor to approve your
numbers before you begin making the solutions.
CHEM 121 Lab Manual F2019
page 101
CHEM 121 Lab Manual F2019
page 102
CHEM 121: Kinetics:
The Clock Reaction
Name: _________________________________
Partner: ________________________________
DATA
Part I: SOLUTION PREPARATION
LAB REPORT
Part A.
1. If bisulfite’s formula is HSO3-, write the formula of sodium bisulfite: _________________
2. Calculate the mass of sodium bisulfite required to prepare 100.0 mL of a 0.0200M sodium
bisulfite solution in water, then record the calculated mass in the Data Table below. Show
your work here:
Calculated
Mass of sodium bisulfite required to
prepare 100.0 mL of a 0.0200M
sodium bisulfite solution.
Actual Amount Used
Part B.
1. If iodate’s formula is IO3-, write the formula of potassium iodate: ____________________
2. Use M1V1=M2V2 to calculate the volume of the original 0.100 M potassium iodate solution
required to prepare 100.0 mL of a 0.0200 M solution. Record the calculated volume below,
and show your work here:
Volume of original 0.100 M potassium iodate
solution required to prepare 100.0 mL of a 0.0200M solution: _____________________
CHEM 121 Lab Manual F2019
page 103
Part II: Running the reaction
Volume of 0.0200 M potassium iodate used for each trial: ______________________
Volume of 0.0200 M sodium bisulfite used for each trial: ______________________
Trial #
1
2
3
Time (in seconds)
Temperature
Average Time for Trials 1-3: _______________________
Part III:
Trial #
Volume of 0.0200M
sodium bisulfite
Volume of 0.0200M
potassium iodate
Volume of
water
4
10.00 mL
8.00 mL
2.00 mL
5
10.00 mL
5.00 mL
5.00 mL
6
8.00 mL
10.00 mL
2.00 mL
7
5.00 mL
10.00 mL
5.00 mL
Time (s)
Part IV:
A. Reaction at a Higher Temperature
Volume of 0.0200 M potassium iodate used for the trial: ______________________
Volume of 0.0200 M sodium bisulfite used for the trial: _______________________
Temperature of warm water bath: ______________ Time for reaction: ______________
B. Reaction at a Lowered Temperature
Volume of 0.0200 M potassium iodate used for the trial: ______________________
Volume of 0.0200 M sodium bisulfite used for the trial: _______________________
Temperature of cold-water bath: ______________ Time for reaction: ______________
CHEM 121 Lab Manual F2019
page 104
Data
Analysis
Indicate the Molar Concentration for the solutions before they were mixed:
Molarity of sodium bisulfite
(from actual mass used): __________________
Molarity of
potassium iodate: ________________
Use M1V1=M2V2 to calculate the molar concentration of sodium bisulfite and
potassium iodate after mixing for each of the solutions. Remember to include the
volume of water added along with the solutions used for V2. (Show your work on a
separate piece of paper and include it with your Lab Report.)
Fill in the table below with the calculated molar concentrations, and then transfer the
reaction times recorded for trials 1-7 in Parts II and III on your Lab Report. Note that
your calculated concentrations will be the same for Trials 1, 2 and 3 because you used
the same volumes of stock solutions for these trials.
Trial #
Molar Concentration of
sodium bisulfite after
mixing
Molar Concentration of
potassium iodate after
mixing
Time (s)
1
2
3
4
5
6
7
1. Compare the reaction time for each of the trials with the concentration of each
solution used. Based on the results, explain the effect of the concentration of
reactants on the rate of a reaction and how that relates to Collision Theory—i.e.,
explain how the collisions between reactant particles are affected by the changes
in concentrations.
CHEM 121 Lab Manual F2019
page 105
2. Consider the data in the table above and imagine that you had run the reaction
with only 5.00 mL of 0.0200M potassium iodate, 5.00 mL of 0.0200M sodium
bisulfate, and no added water. How would the reaction time compare to the
average time of trials 1-3? Explain.
3. Compare the data obtained in Part IV to the average time calculated in Part II.
Summarize what you observed about the effect of the temperature on the rate of a
reaction and how that relates to Collision Theory. Specifically, explain how the
collisions between reactant particles are affected by the changes in temperature.
CHEM 121 Lab Manual F2019
page 106
Part II: Running the reaction
Volume of 0.0200 M potassium iodate used for each trial: ______________________
Volume of 0.0200 M sodium bisulfite used for each trial: ______________________
Trial #
1
2
3
Time (in seconds)
Temperature
Average Time for Trials 1-3: _______________________
Part III:
Trial #
Volume of 0.0200M
sodium bisulfite
Volume of 0.0200M
potassium iodate
Volume of
water
4
10.00 mL
8.00 mL
2.00 mL
5
10.00 mL
5.00 mL
5.00 mL
6
8.00 mL
10.00 mL
2.00 mL
7
5.00 mL
10.00 mL
5.00 mL
Time (s)
Part IV:
A. Reaction at a Higher Temperature
Volume of 0.0200 M potassium iodate used for the trial: ______________________
Volume of 0.0200 M sodium bisulfite used for the trial: _______________________
Temperature of warm water bath: ______________ Time for reaction: ______________
B. Reaction at a Lowered Temperature
Volume of 0.0200 M potassium iodate used for the trial: ______________________
Volume of 0.0200 M sodium bisulfite used for the trial: _______________________
Temperature of cold-water bath: ______________ Time for reaction: ______________
CHEM 121 Lab Manual F2019
page 104
Data
Analysis
Indicate the Molar Concentration for the solutions before they were mixed:
Molarity of sodium bisulfite
(from actual mass used): __________________
Molarity of
potassium iodate: ________________
Use M1V1=M2V2 to calculate the molar concentration of sodium bisulfite and
potassium iodate after mixing for each of the solutions. Remember to include the
volume of water added along with the solutions used for V2. (Show your work on a
separate piece of paper and include it with your Lab Report.)
Fill in the table below with the calculated molar concentrations, and then transfer the
reaction times recorded for trials 1-7 in Parts II and III on your Lab Report. Note that
your calculated concentrations will be the same for Trials 1, 2 and 3 because you used
the same volumes of stock solutions for these trials.
Trial #
Molar Concentration of
sodium bisulfite after
mixing
Molar Concentration of
potassium iodate after
mixing
Time (s)
1
2
3
4
5
6
7
1. Compare the reaction time for each of the trials with the concentration of each
solution used. Based on the results, explain the effect of the concentration of
reactants on the rate of a reaction and how that relates to Collision Theory—i.e.,
explain how the collisions between reactant particles are affected by the changes
in concentrations.
CHEM 121 Lab Manual F2019
page 105
2. Consider the data in the table above and imagine that you had run the reaction
with only 5.00 mL of 0.0200M potassium iodate, 5.00 mL of 0.0200M sodium
bisulfate, and no added water. How would the reaction time compare to the
average time of trials 1-3? Explain.
3. Compare the data obtained in Part IV to the average time calculated in Part II.
Summarize what you observed about the effect of the temperature on the rate of a
reaction and how that relates to Collision Theory. Specifically, explain how the
collisions between reactant particles are affected by the changes in temperature.
CHEM 121 Lab Manual F2019
page 106
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Kinetics Lab Report
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Upload an image of pages 104 and 105 from the Kinetics Post-lab report with the values filled in.
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(You can use the “show work” box if you need multiple file uploads. If you have p. 104-105 in a single
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Questio
Compare the reaction time for each of the trials with the concentration of each solution used.
Based on the results, explain the effect of the concentration of reactants on the rate of a reaction and
how that relates to Collision Theory—i.e., explain how the collisions between reactant particles are
affected by the changes in concentrations.
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Consider the data in the table above and imagine that you had run the reaction with only 5.00 mL of
0.0200M potassium iodate, 5.00 mL of 0.0200M sodium bisulfate, and no added water.
Questio
How would the reaction time compare to the average time of trials 1-3? Explain.
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Compare the data obtained in Part IV to the average time calculated in Part II. Summarize what you
observed about the effect of the temperature on the rate of a reaction and how that relates to Collision
Theory.
Questio
Specifically, explain how the collisions between reactant particles are affected by the changes in
temperature.
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