Investigating Indicators
Recommended for grades 9–12.
Introduction
An indicator solution does what its name suggests – it indicates. In chemistry, a common use of an indicator is to signal the equivalence point of a reaction between an acid and a base. Generally, an indicator is itself a weak organic acid or a blend of weak organic acids. The indicator establishes equilibrium in aqueous solution, which is shifted according to LeChatelier’s principle as the solution changes in pH. The indicator is one color in the presence of a range of concentrations of H+ or OH– ions, and another color when the acidity changes. Knowing when an indicator will change color helps you determine the precise equivalence point of an acid-base reaction. This knowledge is also important as you select the proper indicator for a given reaction.
Objectives
In this experiment, you will
- Conduct strong acid-strong base titrations using solutions of hydrochloric acid and sodium hydroxide, and three different indicator solutions.
- Select the proper indicator to use with a titration involving a weak acid or a weak base, based on your observations and measurements.
Sensors and Equipment
This experiment requires each of the following Vernier sensors and equipment (unless otherwise noted):
Drop Counter (optional)
Additional Requirements
You may also need an interface and software for data collection. What do I need for data collection?
Download Experiment Preview
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.
Standards Correlations
See all standards correlations for Advanced Chemistry with Vernier »
Included in the Lab Book
Vernier lab books include a CD with word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.