Electrolytic Cells
These cells USE electrical energy to cause a chemical reaction. They use a battery.
N.B.
1. Electrical energy is converted into chemical energy.
2. Electrolysis is the use of electricity to cause a chemical reaction.
3. Electrolyte – a solution that conducts electricity as a result of dissolved ions – ions move in opposite directions in the liquid in order to conduct the electrical energy.
4. Electrolysis – used for electroplating, and to make new chemicals.
Assume that CuCl2 is dissolved in a beaker of water.
Study the diagram.
Two carbon rods are connected to a battery and placed into the solution.
The left hand side rod is positive because it is connected to the positive terminal of the battery.
The other rod is negative because it is connected to the negative terminal of the battery.
The left hand side rod is positive because it is connected to the positive terminal of the battery.
The other rod is negative because it is connected to the negative terminal of the battery.
The electrodes get their signs because of how they are connected to the battery, and NOT because of a chemical reaction.
Now the ions are attracted to the opposite rods as shown in the diagram.
The Cl-1 ions move towards the positive rod.
The following reactions occur at this electrode. Cl-1 → Cl + e
Cl-1 → Cl + e
2Cl-1 → Cl2 + 2e
The following reactions occur at this electrode. Cl-1 → Cl + e
Cl-1 → Cl + e
2Cl-1 → Cl2 + 2e
This is an OXIDATION 1/2 REACTION
Therefore this electrode is called an ANODE.
Remember it is already POSITIVE because it is connected to the positive of the battery.
Chlorine gas Cl2(g) will form here.
The Cu2+ ions move towards the negative rod.
The following reaction occurs at this electrode.
Therefore this electrode is called a CATHODE.
Remember it is already NEGATIVE because of the battery.
The following reaction occurs at this electrode.
Cu2+ + 2e → Cu(s)
Therefore this electrode is called a CATHODE.
Remember it is already NEGATIVE because of the battery.
The CATHODE gets COATED with the COPPER ATOMS.