Conductimetric Titrations

Recommended for grades 9–16.

Figure from experiment 18 from Investigating Chemistry through Inquiry

Introduction

There are a number of ways to investigate a chemical reaction. Measuring temperature change, pressure change, pH change, and/or conductivity change are some of the ways. A titration is a process used to determine the volume of a solution needed to react with a given amount of another substance. You have probably done pH titrations in other experiments; now you will be performing conductivity titrations. In the Preliminary Activity, you will titrate a solution of the strong acid hydrochloric acid, HCl, with a solution of the strong base sodium hydroxide, NaOH. The concentration of the NaOH solution is given, and you will determine the unknown concentration of the HCl. Hydrogen ions from the HCl react with hydroxide ions from the NaOH in a one-to-one ratio to produce water in the overall reaction:

${{\text{H}}^{\text{ + }}}{\text{(aq) + C}}{{\text{l}}^ - }{\text{(aq) + N}}{{\text{a}}^{\text{ + }}}{\text{(aq) + O}}{{\text{H}}^ - }{\text{(aq)}} \to {{\text{H}}_{\text{2}}}{\text{O(l) + N}}{{\text{a}}^{\text{ + }}}{\text{(aq) + C}}{{\text{l}}^ - }{\text{(aq)}}$

Objectives

You will determine the volume of NaOH titrant used at the equivalence point using the intersection of the linear fits of the two branches of the resulting curve. The volume of NaOH titrant used at the equivalence point will be used to determine the molarity of the HCl.

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

Sensors and Equipment

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

Conductivity Probe

Additional Requirements

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

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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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