Electrolysis is carried out by dipping two electrodes connected to a DC supply into a solution of an electrolyte or a molten electrolyte. One electrode is attached to the negative side of the power source and the other to the positive side. In industry, electrolysis is used in many ways. Fore xample, the production of aluminum so learn the Hall-Heroult process well. Other examples of real life electrolysis are the production of sodium hydroxide and chlorine by the electrolysis of brine, and the refining of the metal copper. If you know the principles of electrolysis plus these examples, you... Show more Electrolysis is carried out by dipping two electrodes connected to a DC supply into a solution of an electrolyte or a molten electrolyte. One electrode is attached to the negative side of the power source and the other to the positive side. In industry, electrolysis is used in many ways. Fore xample, the production of aluminum so learn the Hall-Heroult process well. Other examples of real life electrolysis are the production of sodium hydroxide and chlorine by the electrolysis of brine, and the refining of the metal copper. If you know the principles of electrolysis plus these examples, you should cope easily with any questions that you come across. The key to understanding what is happening during electrolysis is to remember two basic facts - one is about electricity, the other is about chemical bonding. Firstly, keep in mind that electricity is a flow of electrons pumped round a circuit in one direction by a power supply (e.g. power pack, battery) and secondly, ionic bonding involves the loss and gain of electrons. Opposite electrical charges attract one another so the positive ions in the electrolyte move towards the negative electrode and vice-versa. Positive ions are called cations and so the negative electrode is called the cathode because it attracts the cations. The positive electrode attracts the anions and is therefore called the anode. During electrolysis in solution, oxygen is usually produced at the anode as anions are very stable. When a cation reaches the cathode, one or more electrons are transferred to the cation, canceling out its positive charge. Most cations are metals so when they gain an electron, they become metal atoms and are deposited on the cathode. What happens then depends on the reactivity of the metal and whether the electrolysis is being carried out in solution or using a molten electrolyte. If the electrolysis is being carried out in solution, hydrogen will be produced if the metal in solution is higher in the reactivity series e.g. sodium, potassium. Less reactive metals will form a deposit on the cathode and, as the thickness of the deposit increases, some of the deposit will flake off and be seen on the bottom of the electrolysis vessel. In a molten solution, where water is not present, the metal atoms are always produced - this is how reactive metals like sodium and potassium are extracted from their ores. Michael Faraday also introduced the terms used in electrolysis that you are familiar with such as anode, cathode, electrode, and io. Once electricity generating equipment had improved and electrolysis was better understood, the commercial value of the process was realized and it was taken up by industry. The first large scale electrolytic cells were developed in the 1880s for the electrolysis of brine which gave birth to the chlor-alkali industry. Also during the same decade, the Hall-Héroult process for the extraction of aluminum was developed which transformed aluminum from a rarely seen and extremely expensive metal into the cheap and widely used metal of today. There were no health and safety at work regulations at the time and workers in both industries could expect short lives due to the toxic and corrosive nature of the chemicals involved. For the high school, you should know how electrolysis works for both processes and the main uses of the products. Show less
Electrolysis is carried out by dipping two electrodes connected to a DC supply into a solution of an electrolyte or a molten electrolyte. One electrode is attached to the negative side of the power source and the other to the positive side.
In industry, electrolysis is used in many ways. Fore xample, the production of aluminum so learn the Hall-Heroult process well. Other examples of real life electrolysis are the production of sodium hydroxide and chlorine by the electrolysis of brine, and the refining of the metal copper. If you know the principles of electrolysis plus these examples, you should cope easily with any questions that you come across.
The key to understanding what is happening during electrolysis is to remember two basic facts - one is about electricity, the other is about chemical bonding. Firstly, keep in mind that electricity is a flow of electrons pumped round a circuit in one direction by a power supply (e.g. power pack, battery) and secondly, ionic bonding involves the loss and gain of electrons.
Opposite electrical charges attract one another so the positive ions in the electrolyte move towards the negative electrode and vice-versa. Positive ions are called cations and so the negative electrode is called the cathode because it attracts the cations. The positive electrode attracts the anions and is therefore called the anode. During electrolysis in solution, oxygen is usually produced at the anode as anions are very stable.
When a cation reaches the cathode, one or more electrons are transferred to the cation, canceling out its positive charge. Most cations are metals so when they gain an electron, they become metal atoms and are deposited on the cathode. What happens then depends on the reactivity of the metal and whether the electrolysis is being carried out in solution or using a molten electrolyte.
If the electrolysis is being carried out in solution, hydrogen will be produced if the metal in solution is higher in the reactivity series e.g. sodium, potassium. Less reactive metals will form a deposit on the cathode and, as the thickness of the deposit increases, some of the deposit will flake off and be seen on the bottom of the electrolysis vessel. In a molten solution, where water is not present, the metal atoms are always produced - this is how reactive metals like sodium and potassium are extracted from their ores.
Michael Faraday also introduced the terms used in electrolysis that you are familiar with such as anode, cathode, electrode, and io.
Once electricity generating equipment had improved and electrolysis was better understood, the commercial value of the process was realized and it was taken up by industry. The first large scale electrolytic cells were developed in the 1880s for the electrolysis of brine which gave birth to the chlor-alkali industry. Also during the same decade, the Hall-Héroult process for the extraction of aluminum was developed which transformed aluminum from a rarely seen and extremely expensive metal into the cheap and widely used metal of today. There were no health and safety at work regulations at the time and workers in both industries could expect short lives due to the toxic and corrosive nature of the chemicals involved. For the high school, you should know how electrolysis works for both processes and the main uses of the products.
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