 We're going to perform a series of demonstrations to look at the electrolysis of aqueous solutions. In electrolysis reaction, you pass electrical current through the cell in order to produce some non-spontaneous reactions. When you electrolyze an aqueous solution, you need to take into account not only the oxidation and reduction of the ions in the solution, but also the oxidation and reduction of the water and the oxidation and reduction of the electrodes. We will use both reactive metal electrodes and inert electrodes. In the electrolysis, you are doing a non-spontaneous reaction. So we're going to be looking for the half cell reactions with the least negative voltage. And we'll look at each half cell independently. We'll attach the black lead to the cathode. The black lead is where electrons leave the external circuit and enter the solution. This is where reduction takes place. The red lead is attached to the anode. This is where electrons leave the solution and enter the external circuit. This is where oxidation takes place. We placed a one molar solution of sodium sulfate in the YouTube. We've added some bromethymol blue to the solution. The solution is green because the pH of the sodium sulfate is 7. We've put two graphite rods into the YouTube. These are inert electrodes. We attach our black and red lead to the electrodes. As we pass current through the half cell, the sodium ion is not easily reduced. The water is more easily reduced than the sodium ion. So at the cathode, the black lead, we see that we have gas evolved, which is hydrogen gas. We also see that the solution is turning blue indicating that that solution is basic. We're getting the reduction of water to produce hydrogen gas and hydroxide ion. The hydroxide ion turns the solution blue. At the anode, we see that we're also getting gas evolved. Sulfate ion is not easily oxidized. The water is more easily oxidized than the sulfate ion. We oxidize the water to form oxygen gas and hydrogen ions. The solution becomes acidic and the indicator turns from green to yellow.