Electrolysis Electrolysis is splitting up a compound by passing electricity through it.
An electrolyte is a substance that will conduct electricity when molten or dissolved in water.
Electrodes are two rods that dip into an electrolyte and complete the electrical circuit. There is a positive and a negative electrode.
a F Electrolytes are
important for cells to function properly. When you exercise heavily, you lose electrolytes in your sweat, in particular sodium and potassium. These electrolytes must be replaced. Many sports drinks have sodium chloride or potassium chloride added to them for this reason.
Splitting Water
In 1781, English scientist Henry Cavendish showed that water was produced through the combustion of hydrogen and oxygen. This proved that water is in fact a compound and not an element.
Water can also be split into hydrogen and oxygen by passing an electric current through it. This is known as the electrolysis of water.
The piece of equipment used in the electrolysis of water is a Hofmann voltameter.
The battery supplies the electrical energy for the reaction. The electrolyte in the reaction is water and some dilute sulfuric acid. The electrodes can be made of either platinum or carbon.
The word equation for the splitting of water is: Water → hydrogen + oxygen
Electrolysis of water
During the electrolysis of water, twice as much of one gas is produced as another. Look at Fig. 22.3.6.
1. Which gas has twice the volume of the other? 2. Explain this observation. 3. How would you test each gas to make sure you were correct?
391 z
Water with sulfuric acid
22.3
Learn more about electrodes in Physical World 18.6
Electrolysis in action
Using a Hofmann voltameter, carry out the electrolysis of water in the school laboratory. Record your observations.
