23.1. Electrochemical Cells http://www.ck12.org
FIGURE 23.1
Diagram of a voltaic cell consisting of zinc
and copper half-cells.the reaction. Since zinc ions are a product of the reaction, the zinc ion concentration in the half-cell increases.
Because a surplus of electrons is generated at the anode, it is labeled as the negative electrode.- The electrons that are generated at the zinc anode travel through the external wire and register a reading on
the voltmeter. They continue to the copper electrode. - Electrons enter the copper electrode where they combine with the copper(II) ions in the solution, reducing
them to copper metal.The electrode at which reduction occurs is called thecathode. The cathode gradually
increases in mass because of the production of copper metal. The concentration of copper(II) ions in the
half-cell solution decreases. The cathode is the positive electrode. - Ions move through the salt bridge to maintain electrical neutrality in the cell. Negative ions move toward
the anode to compensate for the production of positive zinc ions. Positive ions move toward the cathode to
compensate for the consumption of positive copper(II) ions.
The two half-reactions can again be added together to provide the overall redox reaction occurring in the voltaic cell.
Zn(s) + Cu^2 +(aq)âZn^2 +(aq) + Cu(s)Notice in the figure above (Figure23.1) that the reading on the voltmeter is 1.10 volts (V). This will be the electrical
potential (voltage) in a zinc-copper cell when the ion concentrations are both 1.0 M. You will learn how to determine
cell voltages in the following lesson.
There is a simple shorthand notation used to illustrate a particular electrochemical cell. The cell notation for the
zinc-copper cell is shown below.
Zn(s) | Zn^2 +(1 M) || Cu^2 +(1 M) | Cu(s)