Conductimetric Titration and Gravimetric Determination of a Precipitate

Introduction

In this experiment, you will monitor conductivity during the reaction between sulfuric acid, H₂SO₄, and barium hydroxide, Ba(OH)₂, in order to determine the equivalence point. From this information, you can find the concentration of the Ba(OH)₂ solution. The reaction between sulfuric acid and barium hydroxide yields an insoluble product, barium sulfate, and water, as shown in the reaction equation below.

In this reaction, the total number of dissociated ions in solution is reduced dramatically during the reaction as a precipitate is formed. As 0.100 M H₂SO₄ is slowly added to Ba(OH)₂ of unknown concentration, changes in the conductivity of the solution will be monitored using a Conductivity Probe. When the probe is placed in a solution that contains ions, and thus has the ability to conduct electricity, an electrical circuit is completed across the electrodes that are located on either side of the hole near the bottom of the probe body. This results in a conductivity value that can be read by the interface. The unit of conductivity used in this experiment is the microsiemens/cm, or µS/cm.

In addition, you will capture the precipitate, and measure its mass. You will have two methods, therefore, of calculating the molar concentration of a barium hydroxide solution that is titrated with a sulfuric acid solution of known concentration.

Objectives

In this experiment, you will

• Measure the conductivity of the reaction between sulfuric acid and barium hydroxide.
• Use conductivity values as a means of determining the equivalence point of the reaction.
• Measure the mass of a product of the reaction as a means of determining the equivalence point of the reaction gravimetrically.
• Calculate the molar concentration of a barium hydroxide solution.