Electrochemistry Tutorial: Galvanic Cells and the Nernst Equation >> Introduction

Electrochemistry: Galvanic Cells and the Nernst Equation

Introduction

In this experiment the goal is to investigate how to generate an electric current from a spontaneous redox chemical reaction. The device in which chemical energy is changed to electrical energy is called a galvanic cell. Batteries are an everyday example of galvanic cells.

In this experiment:

• We will build and investigate several galvanic cells.
• We will investigate the chemical reactions taking place in various galvanic cells and measure the cell potentials.
• We will study the electrodes that can be combined in various ways to form many different galvanic cells. We will determine the potential of these cells under standard conditions.
• We will investigate how the potential of the galvanic cell changes when we depart from the conditions defined as a "standard" and use the Nernst Equation to predict these changes.

The experimental strategy is shown below in the following 4 steps:

Step 1



Action: Dip a strip of metal in a salt solution of another metal. Repeat with different metal/salt combinations.
Result: The observations provide evidence of whether or not a spontaneous reaction takes place. If a reaction is observed, we can use our knowledge of the chemical species involved to figure out the chemical reaction.

Step 2


Action: Create several half-cells, each consisting of a metal strip (an electrode) dipped in solution of that metal’s salt (an electrode solution). Combine various half-cells into pairs (galvanic cells) and try them out to power a stopwatch.
Result: We identify the galvanic cells which provide enough voltage to power a stopwatch.

Step 3


Action: Combine various half-cells into pairs (galvanic cells) and measure the voltage of the various pairs of half-cells.
Result: Create a series of electrode potentials arranged in order of the tendency of a metal ion to undergo reduction.

Step 4


Action: We measure voltage of a cell under standard conditions (1.0 M concentration). We change the concentration of one of the half-cells and observe the effect on the cell voltage. We repeat with various half-cell combinations.
Result: We determine the values of cell voltage under non-standard conditions.

The following pages contain tutors to assist you with understanding and applying some concepts required in the above steps. Please click next to continue to the online activity.