Understand the function of a galvanic cell and calculate its standard cell potential using standard electrode potentials.
Explanation of Galvanic vs Electrolytic cells based on opposing external potential.
A galvanic cell converts the chemical energy of a spontaneous redox reaction into electrical energy. A classic example is the Daniell cell, built with zinc and copper electrodes dipping into their respective salt solutions.
The overall spontaneous cell reaction is:
(Eq. 2.1)
Apparatus diagram of the Daniell cell under opposing potentials.
A clean scientific apparatus-diagram showing three states of a Daniell cell with an opposing external voltage applied. S…
Comparison of anode and cathode properties in a galvanic cell.
Defining cell potential and the Standard Hydrogen Electrode.
The potential difference between the two electrodes of a galvanic cell is called the cell potential (measured in volts). When no current is drawn, it is called the cell electromotive force (emf).
By convention, we place the anode on the left and the cathode on the right. The standard cell potential is calculated as:
Formula for Standard Cell Potential.
Symbol Legend:
Critical Condition:
Always use standard reduction potentials for both values. Do not reverse the sign of the anode potential before subtracting!
Example (Daniell Cell):
Calculate standard cell potential for a given reaction.
To calculate the standard cell potential for the reaction , we first identify the half-reactions. The silver ions () are being reduced to silver metal, so the silver half-cell acts as the . The nickel solid () is being oxidized to nickel ions (), meaning the nickel half-cell acts as the . We use the standard formula to find the overall cell potential. Substituting the given standard reduction potentials of for silver and for nickel, we set up the equation as . Calculating this difference yields a final standard cell potential of .
Identify substances that can oxidise ferrous ions.
An engineer needs an oxidizing agent to convert aqueous into for a wastewater treatment process. Given that the standard reduction potential for is , which of the following halogens CANNOT be used to spontaneously perform this oxidation?