Name ____________________________________ Redox titration of Hydrogen Peroxide
5H2O2 + 2KMnO4 + 3H2SO4  5O2 + 2MnSO4 + 8H2O + K2SO4
(hydrogen peroxide) ( potassium permanganate)
(sulfuric acid)
(oxygen)
(manganese sulfate)
(water)
(potassium sulfate)
Purpose: To determine the % hydrogen peroxide in the hydrogen peroxide solution you can buy at the store.
Hint: The permanganate ion (MnO4-) has a dark purple color. All other species in the reaction are colorless.
Pre-Lab
1.
2.
3.
4.
5.
6.
Assign oxidation numbers to every atom in the above equation.
What element is oxidized?
What element is reduced?
What is the mole ratio of hydrogen peroxide to permanganate ion?
If KMnO4 reacts with an excess of H2O2 in sulfuric acid, what color will result?
If KMnO4 reacts with H2O2 in sulfuric acid, how will you know when all the H2O2 has been
completely oxidized?
Procedure
1. Obtain about 35 mL of potassium permanganate solution in a small beaker.
2. Use about 5 mL of the potassium permanganate solution to rinse the buret. Collect the rinse in
a waste beaker.
3. Fill the buret with the potassium permanganate solution.
4. Record the initial volume of solution in the buret. (Read the bottom of the meniscus and report
to the correct number of significant digits.)
5. Using a pipet, transfer 1.00 mL of the store-bought hydrogen peroxide solution into a 125 mL
flask.
6. Add about 25 mL of distilled water to the flask.
7. Measure 5 mL of 6M sulfuric acid into a graduated cylinder and carefully add to the flask. Swirl
gently to mix.
8. Position the flask under the buret so the tip of the buret is within the neck of the flask. Place a
piece of white paper under the flask to make it easier to see the color change.
9. Open the buret stopcock and allow 6-8 mL of the potassium permanganate solution to flow into
the flask. Swirl the flask and note any color changes.
10. Continue to add the potassium permanganate solution slowly, drop-by-drop, while swirling the
flask. You can rinse any permanganate off the inside walls of the flask using distilled water.
11. When a light pink color persists in the solution while swirling the flask, the end-point has been
reached. Record the final volume of the permanganate solution.
12. Empty the flask into the sink and rinse with tap water followed by distilled water.
13. Repeat steps 4—12 for trial two. If your results are not consistent, do a third trial.
14. Clean up
15. Calculate
Name ____________________________________ Redox titration of Hydrogen Peroxide
5H2O2 + 2KMnO4 + 3H2SO4  5O2 + 2MnSO4 + 8H2O + K2SO4
(hydrogen peroxide) ( potassium permanganate)
(sulfuric acid)
(oxygen)
(manganese sulfate)
(water)
(potassium sulfate)
Data table:
Trial 1
Trial 2
Trial 3
Molarity of KMnO4
solution
Initial buret reading
(mL)
Final buret reading
(mL)
Volume of KMnO4
added to the flask (mL)
Calculations
Moles of permanganate ion (MnO4-)
added to flask (Show work!)
Moles of H2O2 oxidized
(Show work!)
Grams of H2O2 oxidized
(Show work!)
% by mass of H2O2 in the storebought solution (assume density of
the solution to be 1.00 g/mL)
(Show work!)
1. According to the label on the bottle of H2O2 from the store, what is the % H2O2 in the storebought solution?
2. According to the titration you performed, is the % H2O2 higher or lower than what it says on
the label?
3. What are some reasons why your experimental value does not match the label?