Honors Chemistry
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Factors that Affect the Rate of a Reaction
Introduction:
There are three common factors that can change the rate at which a chemical reaction happens.
These include temperature, concentration and particle size. A fourth way in which reaction rates
can be altered is through the addition of a catalyst. The effects of concentration, temperature
and catalyst on reaction rate will be addressed in this lab.
Background:
Household hydrogen peroxide (H2O2) is an aqueous solution that has approximately 3%
hydrogen peroxide by volume. Over time, hydrogen peroxide decomposes to yield water and
oxygen gas. This process can be accelerated by the addition of a catalyst. The effects of
temperature and concentration on the decomposition of hydrogen peroxide will be monitored in
this lab. Potassium iodide will be used as a catalyst. Dish detergent will be added to the
system to capture the oxygen gas generated in the reaction. The rise in soap bubbles will be
used to monitor reaction rates.
Materials: Hydrogen Peroxide (3%), Hydrogen Peroxide (7.5%), Potassium Iodide, 50 ml
graduated cylinder, 100ml graduated cylinder, 1000ml graduated cylinder, dish soap,
thermometer, ice, deionized water, warm water (50°C-55°C), 600 ml beaker, timer/watch,
disposable pipettes & small plastic cups (for soap), balance, weigh boats, [hot plate & hot hands
(optional)]
Safety: SDS is available for Hydrogen Peroxide which can burn the skin and the reaction may
cause burns. Goggles must be worn throughout the experiment. KI may stain skin and clothing.
Hot glass looks like cold glass – take heat precautions if necessary.
Pre-lab questions:
1. Briefly describe the four factors that influence the rate of reaction, be sure to explain how
these factors influence the reaction (on a molecular level). How would
increasing/decreasing any of these factors affect the rate of reaction?
a)
b)
c)
d)
2. Write the balanced chemical equation (including states of matter) to describe the reaction
being tested in the lab.
3. Potassium iodide serves as a catalyst for this reaction. Explain the role of a catalyst.
See if you can identify how KI accelerates the decomposition of H2O2.
4. Review the procedures so you can complete this lab efficiently. Create notes here that
will help you move efficiently throughout the lab.
Procedures:
1. Dependence of Reaction Rate on Temperature
Part 1A - Room Temperature:
1. Put 40 ml of hydrogen peroxide in a 100 mL graduated cylinder.
2. Add 5-10 drops of dish soap and gently swirl the graduated cylinder.
3. Measure and record the temperature of the solution.
4. To start the reaction, add 0.3 g of KI and stir. Record the foam height at 10 second
intervals for 60 seconds (initial foam height = 0 mL).
5. Rinse the graduated cylinder for additional use.
Part 1B - Ice Bath
1. Repeat the experiment at a lower temperature by putting about 400 mL of a mixture of
ice and water into a 600 mL beaker.
2. Prepare the sample as done previously but this time place the 100 mL graduated
cylinder in the ice water.
3. Record the starting temperature before adding the KI.
4. Add the KI and record foam height for 60 seconds.
5. Rinse the graduated cylinder for additional use.
Part 1C - Hot Water Bath
1. Repeat the experiment at a higher temperature by putting about 400 mL of how water
(50-60°C) into a 600 ml beaker
2. Prepare the sample as done previously but this time place the 100 mL graduated
cylinder in the hot water.
3. Record the starting temperature before adding the KI.
4. At the KI and record foam height for 60 seconds.
5. Rinse the graduated cylinder for additional use.
2. Dependence of reaction rate on concentration
You will repeat the room temperature experiment (1A) using a peroxide solution that is half
the concentration. Then repeat using double (2X) the concentration of peroxide solution.
Part 2A - Room Temperature with a decrease (1/2) in H2O2 concentration
1. Put 20 ml of hydrogen peroxide in the 100 ml graduated cylinder.
2. Add 20 ml of distilled water to dilute the peroxide solution.
3. Add 5-10 drops of dish soap and gently swirl the graduated cylinder.
4. To start the reaction, add 0.3 g of KI and stir. Record foam height as done in previous
trials.
5. Rinse the graduated cylinder for additional use.
**Part 2B - Room Temperature with an increase concentration (≈2X–6%) of peroxide
solution.** Will be done as a class demo
1. Put 40 ml of the concentrated hydrogen peroxide into the 1000 ml graduated cylinder.
2. Add 5-10 drops of dish soap and gently swirl the graduated cylinder.
3. To start the reaction, add 0.3 g of KI and stir. Record foam height for 60 seconds as
done in previous trials.
Data Tables:
1A) Reaction rate at room temperature
Time (s)
0
10
20
30
40
50
60
-------------------------------
Foam Height
(mL)
Reaction rate
(mL/s)
Avg. Reaction Rate (mL/s):
1A Observations:
1B) Reaction rate at reduced temperature (ice bath)
Time (s)
0
10
20
30
40
50
60
-------------------------------
Foam Height
(mL)
Reaction rate
(mL/s)
Avg. Reaction Rate (mL/s):
1B Observations:
1C) Reaction rate at elevated temperature (hot water bath)
Time (s)
0
10
20
30
40
50
60
------------------------------1C) Observations:
Foam Height
(mL)
Avg. Reaction Rate (mL/s):
Reaction rate
(mL/s)
2A) Reaction rate and decreased reactant concentration
Time (s)
0
10
20
30
40
50
60
-------------------------------
Foam Height
(mL)
Reaction rate
(mL/s)
Avg. Reaction Rate (mL/s):
2A) Observations:
2B) Reaction rate and increase reactant concentration
Time (s)
0
10
20
30
40
50
60
-------------------------------
Foam Height
(mL)
Reaction rate
(mL/s)
Avg. Reaction Rate (mL/s):
2B) Observations:
Post Lab Questions:
1. Review and analyze your data to describe how the parts 1A, 1B, and 1C differed in terms of
the observed reaction rate. Discuss the average reaction rate for each trial.
2. Review and analyze your data to describe how the parts 2A and 2B differed in terms of the
observed reaction rate. Discuss the average reaction rate for each trial.
3. Prepare two graphs comparing time (x-axis) versus foam height (y-axis).
Remember to include a title and labels for each graph.
a. Graph #1 should include 3 separate lines (1A, 1B, 1C) comparing the role of
temperature on foam height. [Note: 1A is the control @ room temperature]
b. Graph #2 should also include 3 separate lines (1A, 2A, 2B) comparing the role of
concentration. [Note: 1A is the control @ 3% H2O2]