Advanced Chemistry Through Inquiry Teacher Guide

(PS-2828)

Teacher manual for AP* and Advanced Chemistry labs. Has both the printed version and a flash drive with teacher tips, a PDF of teacher version and editable Word student version.

Weak Acid Titration

Lab Summary

Weak acids have a slightly different chemistry than strong acids. If the pH of a strong acid solution and a weak acid solution of equal concentration were analyzed, the weaker acid would have a higher pH. This is due to the partial ionization of the weak acid. However, if the weak acid is neutralized by a strong base, the weak acid is forced to ionize completely.

What information can you derive from a pH titration curve of a weak acid?

Theory

Students titrate monoprotic and polyprotic weak acids and determine the relationship between the shapes of the curves and Ka.

Method

The student can reason about the distinction between strong and weak acid solutions with similar values of pH, including the percent ionization of the acids, the concentrations needed to achieve the same pH, and the amount of base needed to reach the equivalence point in a titration. The student can interpret titration data for monoprotic or polyprotic acids involving titration of a weak or strong acid by a strong base (or a weak or strong base by a strong acid) to determine the concentration of the titrant and the pKa for a weak acid, or the pKb for a weak base.

Sensors / Equipment Used:

Advanced Chemistry Sensor

(PS-2172)

Measure pressure, temperature, pH, and conductivity with the Advanced Chemistry Sensor.

PASPORT High Accuracy Drop Counter

(PS-2117)

Is a professional drop counter that allows students to capture detailed titration data. For use with PASPORT Interfaces.

The Associated Bundle:

Chemistry Standard Sensor Bundle

(PS-2927C)

Contains the sensors and probes needed to perform all 17 experiments in the Advanced Chemistry Teacher Guide and all 25 labs in the Chemistry through Inquiry Guide.

Interface Required

This experiment may require software and an interface for data collection.