The Enthalpy of Neutralization of Phosphoric Acid
Recommended for grades 9–12.
Introduction
As you have seen in previous experiments, a great deal can be learned by conducting an acid-base reaction as a titration. In addition, acid-base reactions can be observed and measured thermodynamically. In this case, the reaction is carried out in a calorimeter. If the temperature of the reaction is measured precisely, the enthalpy of neutralization of an acid by a base (or vice versa) can be determined. In this experiment, you will react phosphoric acid with sodium hydroxide.
You will use a Styrofoam cup nested in a beaker as a calorimeter. For purposes of this experiment, you may assume that the heat loss to the calorimeter and the surrounding air is negligible. Phosphoric acid will be the limiting reactant in this experiment, and you will accordingly be determining the enthalpy, ΔH, of neutralization of the acid. Selecting a limiting reactant helps ensure that the temperature measurements and subsequent calculations are as precise as possible.
Objectives
In this experiment, you will
- Measure the temperature change of the reaction between solutions of sodium hydroxide and phosphoric acid.
- Calculate the enthalpy, ΔH, of neutralization of phosphoric acid.
- Compare your calculated enthalpy of neutralization with the accepted value.
Sensors and Equipment
This experiment requires each of the following Vernier sensors and equipment (unless otherwise noted):
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
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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.