Adapted from Advanced Chemistry with Vernier & Laboratory Experiments for Advanced Placement Chemistry by Sally Ann Vonderbrink, Ph. D.Determination of Concentration by Oxidation-Reduction Titration of Hydrogen Peroxide One method of determining the concentration of a hydrogen peroxide, H2O2, solution is by titration with a solution of potassium permanganate, KMnO4, of known concentration. A titration, as you recall, is a convenient method of learning more about a solution by reacting it with a second solution of known molar concentration. There are a number of ways to measure the progress of a titration. The method used in this experiment is called a potentiometric titration, in which the electric potential of a reaction is monitored. All acid-base titrations that are measured by a pH probe are potentiometric; thus, this method is not as unusual as it may seem. The reaction is an oxidation-reduction reaction and proceeds as shown below, in net ionic form. 5 H2O2(aq) + 2 MnO4–(aq) + 6 H+(aq) →5 O2(g) + 2 Mn2+(aq) + 8 H2O (l) In this experiment, you will use an ORP (Oxidation-Reduction Potential) Sensor to measure the potential of the reaction. Your data will look like an acid-base titration curve. The volume of KMnO4titrant used at the equivalence point will be used to determine the concentration of the H2O2solution. Your sample of H2O2will come from a bottle of ordinary, over-the-counter hydrogen peroxide purchased at a grocery or a drug store. The concentration of this product is labeled as 3% (by mass). This experiment illustrates the electrical nature of chemical reactions, and offers practice with a process for observing and measuring an oxidation-reduction reaction. OBJECTIVES In this experiment, you will •Conduct the potentiometric titration of the reaction between commercially available hydrogen peroxide and potassium permanganate. •Measure the potential change of the reaction.