Vernier Software and Technology
Vernier Software & Technology

Using Conductivity to Find an Equivalence Point

Figure from experiment 26 from Chemistry with Vernier

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. You will also see the effect of ions, precipitates, and water on conductivity. The equation for the reaction in this experiment is:

{\text{B}}{{\text{a}}^{{\text{2 + }}}}{\text{(aq)  +  2 O}}{{\text{H}}^{\text{ - }}}{\text{(aq)  +  2 }}{{\text{H}}^{\text{ + }}}{\text{(aq)  +  S}}{{\text{O}}_{\text{4}}}^{{\text{2 - }}}{\text{(aq)}} \to {\text{BaS}}{{\text{O}}_{\text{4}}}{\text{(s)  +  }}{{\text{H}}_{\text{2}}}{\text{O(1)}}

Before reacting, Ba(OH)2 and H2SO4 are almost completely dissociated into their respective ions. Neither of the reaction products, however, is significantly dissociated. Barium sulfate is a precipitate and water is predominantly molecular.

As 0.02 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 microsiemens per centimeter, or μS/cm.

Prior to doing the experiment, it is very important for you to hypothesize about the conductivity of the solution at various stages during the reaction. Would you expect the conductivity reading to be high or low, and increasing or decreasing, in each of these situations?

  • When the Conductivity Probe is placed in Ba(OH)2, prior to the addition of H2SO4.
  • As H2SO4 is slowly added, producing BaSO4 and H2O.
  • When the moles of H2SO4 added equal the moles of BaSO4 originally present.
  • As excess H2SO4 is added beyond the equivalence point.

Objectives

In this experiment, you will

  • Hypothesize about the conductivity of a solution of sulfuric acid and barium hydroxide at various stages during the reaction.
  • Use a Conductivity Probe to monitor conductivity during the reaction.
  • See the effect of ions, precipitates, and water on conductivity.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Chemistry with Vernier »

Chemistry with Vernier

See other experiments from the lab book.

1Endothermic and Exothermic Reactions
2Freezing and Melting of Water
3Another Look at Freezing Temperature
4Heat of Fusion of Ice
5Find the Relationship: An Exercise in Graphing Analysis
6Boyle's Law: Pressure-Volume Relationship in Gases
7Pressure-Temperature Relationship in Gases
8Fractional Distillation
9Evaporation and Intermolecular Attractions
10Vapor Pressure of Liquids
11Determining the Concentration of a Solution: Beer's Law
12Effect of Temperature on Solubility of a Salt
13Properties of Solutions: Electrolytes and Non-Electrolytes
14Conductivity of Solutions: The Effect of Concentration
15Using Freezing Point Depression to Find Molecular Weight
16Energy Content of Foods
17Energy Content of Fuels
18Additivity of Heats of Reaction: Hess's Law
19Heat of Combustion: Magnesium
20Chemical Equilibrium: Finding a Constant, Kc
21Household Acids and Bases
22Acid Rain
23Titration Curves of Strong and Weak Acids and Bases
24Acid-Base Titration
25Titration of a Diprotic Acid: Identifying an Unknown
26Using Conductivity to Find an Equivalence Point
27Acid Dissociation Constant, Ka
28Establishing a Table of Reduction Potentials: Micro-Voltaic Cells
29Lead Storage Batteries
30Rate Law Determination of the Crystal Violet Reaction
31Time-Release Vitamin C Tablets
32The Buffer in Lemonade
33Determining the Free Chlorine Content of Swimming Pool Water
34Determining the Quantity of Iron in a Vitamin Tablet
35Determining the Phosphoric Acid Content in Soft Drinks
36Microscale Acid-Base Titration

Experiment 26 from Chemistry with Vernier Lab Book

<em>Chemistry with Vernier</em> book cover

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Dev Reference: VST0095

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