Oxidation-Reduction Titrations

Recommended for grades 9–16.

Figure from experiment 19 from Investigating Chemistry through Inquiry

Introduction

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. In this experiment, you will use an ORP (Oxidation-Reduction Potential) Sensor to measure the electrical potential of the reaction being studied in a titration.

You will be titrating commercial bleach with hydrogen peroxide of known molarity in order to determine the molarity of the bleach sample. The reaction being studied can be represented as follows:

${\text{NaOCl(aq) + }}{{\text{H}}_{\text{2}}}{{\text{O}}_{\text{2}}}{\text{(aq)}} \to {\text{NaCl(aq) + }}{{\text{H}}_{\text{2}}}{\text{O(l) + }}{{\text{O}}_{\text{2}}}{\text{(g)}}$

where NaOCl is sodium hypochlorite, a representative component of bleach, and H₂O₂ is the formula for hydrogen peroxide. The products are sodium chloride, water, and oxygen. Your sample of H₂O₂ will 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% mass/volume, which is ~0.88 M.

Objectives

In the Preliminary Activity, you will be titrating commercial bleach with hydrogen peroxide of known molarity in order to determine the molarity of the bleach sample.

After completing the Preliminary Activity, you will first use reference sources to find out more about oxidation, reduction, and oxidation-reduction titrations before you choose and investigate a researchable question using oxidation-reduction titrations.

Sensors and Equipment

This investigation requires each of the following Vernier sensors and equipment (unless otherwise noted):

ORP Sensor

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

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The student-version preview includes:

Step-by-step instructions for the Preliminary Activity
List of materials and equipment

Note: The experiment preview of the Preliminary Activity does not include essential teacher information, safety tips, or sample data. Instructions for Logger Pro and other software (such as LabQuest App or TI handheld software, where available) are on the CD that accompanies the book. We strongly recommend that you purchase the book before performing experiments.

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