Microscale Acid-Base Titration

Recommended for grades 9–12.

Figure from experiment 36 from Chemistry with Vernier

Introduction

A titration is a process used to determine the volume of a solution needed to react with a given amount of another substance. In this experiment, you will titrate hydrochloric acid solution, HCl, with a basic sodium hydroxide solution, 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:

${{\text{H}}^{\text{ + }}}{\text{(aq) + C}}{{\text{l}}^{\text{ - }}}{\text{(aq) N}}{{\text{a}}^{\text{ + }}}{\text{(aq) + O}}{{\text{H}}^{\text{ - }}}{\text{(aq)}} \to {{\text{H}}_{\text{2}}}{\text{O(1) + N}}{{\text{a}}^{\text{ + }}}{\text{(aq) + C}}{{\text{l}}^{\text{ - }}}{\text{(aq)}}$

When HCl solution is titrated with NaOH solution, the pH value of the acidic solution is initially low. As base is added, the change in pH is quite gradual until close to the equivalence point, when equimolar amounts of acid and base have been mixed. Near the equivalence point, the pH increases very rapidly. The change in pH then becomes more gradual again, before leveling off with the addition of excess base.

Objectives

In this experiment, you will

Perform a microscale acid-base titration.
Monitor pH.
Determine the approximate concentration of the acid used in the titration.

Sensors and Equipment

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

pH 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 computer-based data collection
List of materials and equipment

Note: The experiment preview of the computer edition 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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