LAB - Percentage of H2O2 in a Drugstore
Bottle of Hydrogen Peroxide
CONTEXT and THEORY
Hydrogen peroxide, H2O2, is easily oxidized. It is used in commercial bleaching processes
and in wastewater treatment plants as an environmentally friendly alternative to chlorine.
Dilute solutions of H2O2 are used to bleach hair and to clean wounds. It readily decomposes
in the presence of light, heat, or metallic catalysts into water and oxygen. It is important to
know the actual concentration of a solution of H2O2 as its effectiveness can decrease with
smaller concentrations.
The purpose of this experiment is to analyze the percent hydrogen peroxide in a common
"drugstore" solution by titrating it with potassium permanganate. Before this titration can be
performed, the potassium permanganate must be standardized. This means that its
concentration must be determined exactly so that it can then be used to determine the
concentration of the hydrogen peroxide.
Standardization of KMnO4
Solutions of potassium permanganate (dark purple in color) are not easily standardized solely
by preparation, as solid potassium permanganate often contains impurities such as chlorides,
sulfates, and nitrates. Potassium permanganate can be standardized in acidic solution with a
known concentration of iron (II) ions. In this oxidation-reduction reaction, manganese (II) ions
and iron (III) ions are formed. The unbalanced redox reaction is shown below:
MnO4- + Fe+2  Mn+2 + Fe+3
Titration of H2O2
Once the potassium permanganate solution is standardized, it will be used to titrate the
hydrogen peroxide solution in the presence of an acid. The manganese ion in KMnO4
undergoes reduction very easily. In acidic solution, permanganate ions (MnO 4)+ from
KMnO4 reduce to nearly colorless manganese ions. In the presence of permanganate ions
in acidic solution, an aqueous solution of H2O2 will undergo oxidation to make oxygen gas
and hydrogen ions. The unbalanced redox reaction is shown below:
MnO4- + H2O2  Mn+2 + O2 + H+
PRE-LAB QUESTIONS
1. Standardization of KMnO4
Balance the reaction given in the theory section, in acid. Show the half reactions, then the
full balanced reaction in the boxes provided.
Reduction half reaction
Oxidation half reaction
Balanced Reaction
2. Titration of H2O2
Balance the reaction given in the theory section, in acid. Show the half reactions, then the
full balanced reaction in the boxes provided.
Reduction half reaction
Oxidation half reaction
Balanced Reaction
PROCEDURE
This lab will be viewed virtually. This is not a lab simulation, rather it is a series of pictures
from the live lab. To complete the lab report and questions, follow the screen shots of the
procedure shown. Several of the procedure pages have multiple photos. Make sure to click
on each one before moving to the next step in the procedure. You will use these photos to
collect your data.
http://resource.rockyview.ab.ca/t4t/chem30/mm/m3/m3_l5_hydrogen_peroxide/m3_l5_hydrog
en_peroxide.html
Ignore any references to module, textbook, or assignment numbers. They do not correspond
to our course. You do not need to complete any questions indicated in the link above. Your
questions and lab requirements are all listed in this document.
DATA
Standardization of KMnO4 (Steps 1-7)
Volume of 0.0500 M FeSO4.(NH4)2SO4.6H2O Titrated = ______________
Trial 1
Trial 2
Trial 3
Trial 4
Trial 3
Trial 4
Initial Volume of
KMnO4 (mL)
Final Volume of
KMnO4 (mL)
Volume of KMnO4
Used (mL)
Titration of H2O2 (Steps 8-12)
Volume of H2O2 Titrated = ______________
Trial 1
Trial 2
Initial Volume of
KMnO4 (mL)
Final Volume of
KMnO4 (mL)
Volume of KMnO4
Used (mL)
CALCULATIONS and RESULTS
Use your pre-lab equations and your data to answer the following questions. Show your work
and indicate your final answer (in bold, color, box, etc)
Concentration of the potassium permanganate solution:
1. Calculate the molarity of the KMnO4 solution for each trial.
2. Calculate the average molarity of the KMnO4 solution.
Concentration of the hydrogen peroxide solution tested:
3. Calculate the moles and mass of H2O2 titrated for each trial.
4. If the density of the H2O2 solution titrated was 1.00 g/mL, calculate the percentage of
H2O2 in solution in each trial.
5. Calculate the average percentage of the H2O2 solution.
POST-LAB QUESTIONS
1. In a titration,
The titrant is located in the ______________.
The analyte is located in the ______________.
2. In the standardization of potassium permanganate:
The titrant was ______________. It’s original color was __________________.
The analyte was ______________. It’s original color was __________________.
The titration was complete when the color changed to __________________.
3. In the titration of hydrogen peroxide.
The titrant was ______________. It’s original color was __________________.
The analyte was ______________. It’s original color was __________________.
The titration was complete when the color changed to __________________.
4. The hydrogen peroxide analyzed says 3% on the bottle. Calculate the percent error.
5. What would cause the average values of the H2O2 concentration to be higher than the
reported values of the H2O2 tested?
6. What would cause the average values of the H2O2 concentration to be lower than the
reported values of the H2O2 tested?
7. How would the concentrations of the KMnO4 and the H2O2 solutions have been affected
if the following observations were made about the Erlenmeyer flask? Justify your
answers.
a. When the titration was completed, the flask was colorless.
b. When the titration was completed, the flask was dark red or purple.
LAB REPORT
A formal report is not required for this lab. Instead, submit the following sections:
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Pre-lab Questions
Data
Calculations
Post-lab Questions
Submit to Dropbox folder: Lab – Percent Hydrogen Peroxide