How do you predict the products of electrolysis?

You predict the products of electrolysis by identifying the ions present and applying the electrochemical series.

Electrolysis is a process that uses an electric current to drive a non-spontaneous chemical reaction. The products of electrolysis can be predicted by identifying the ions present in the electrolyte and applying the electrochemical series, which ranks elements based on their ability to lose or gain electrons.

Firstly, you need to identify the ions present in the electrolyte. The electrolyte is the substance that is being electrolysed and it can be a molten ionic compound or an aqueous solution. In a molten ionic compound, the ions are the positive metal ions and the negative non-metal ions. In an aqueous solution, the ions are the positive metal ions, the negative non-metal ions, and also H+ and OH- ions from water.

Next, you apply the electrochemical series. This is a list of elements in order of their reactivity, with the most reactive at the top and the least reactive at the bottom. During electrolysis, the most reactive ions are preferentially discharged. At the cathode (negative electrode), positive ions gain electrons and are discharged. The metal ions or H+ ions are discharged, depending on their position in the electrochemical series. At the anode (positive electrode), negative ions lose electrons and are discharged. The non-metal ions or OH- ions are discharged, depending on their position in the electrochemical series.

By identifying the ions present and applying the electrochemical series, you can predict the products of electrolysis. For example, if you electrolyse molten sodium chloride, the products are sodium at the cathode and chlorine at the anode. If you electrolyse aqueous sodium chloride, the products are hydrogen at the cathode and chlorine at the anode, because H+ ions are more reactive than Na+ ions.