Electrolytic Cells and Electrolysis

All around us, a number of elements and substances are present, each with their own properties and ability to react with other elements. While we talk about electrolysis, it is amazing to imagine how something as simple as an electric current can alter the composition of an element. When an electrolytic cell comes into play, it leads to a chemical alteration of a substance, which itself, is amazing to study about.

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The Process of Electrolysis

Simply explained, the process of electrolysis refers to decomposition of a given element under the influence of an electric current. The first electrolysis was carried out by Sir Humphrey Davey in the year 1808. This experiment revealed new understandings about the way certain elements behave and how they are different from compounds and ions.

What is an Electrolytic Cell?

As for an electrolytic cell, we can say that in many respects, it is much the same as a galvanic cell as it requires a salt bridge, two electrodes and the flow of electrons from the anode to the cathode. However, the two still manage to be different from each other in many respects. For one, an electrolytic cell converts electrical energy into chemical energy and not the other way round.

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The ensuing redox reaction in the process is not a spontaneous one and for the reaction to start, electric energy has to be introduced in the apparatus. Unlike a galvanic cell, an electrolytic cell requires both metals to be placed in the same container. The positive electrode, in this case, is called the anode and the negative electrode is called the cathode. For the supply of electrons, an external battery is used.

What are the Implications of an Electrolysis Reaction?

There are some fundamental learnings which can be devised out of an electrolysis reaction, which are as follows:

• For the supply of electrons, an external power source has to be employed. This makes an electrolytic cell an almost opposite of a galvanic cell.
• The potential difference between the electrodes is the reason why the transfer of ions takes place.
• Whenever an aqueous solution is subjected to the electrolytic process, water can undergo oxidation and reduction processes and may even become the dominated process in the experiment if a sufficient amount of voltage is applied to the solution.
• The practical applications of the process of electrolysis include refining of metals in heavy industries, production of organic and inorganic products and more, which are later used by other industries for varying purposes.

Faraday’s Law of Electrolysis

As stated in the law of Faraday, when one mole of electric charge is made to pass through an electrolytic cell, it will discharge half a mole of a divalent metal ion. Based on this theory, Faraday devised his two laws of electrolysis which states that the respective weight of a substance formed at an electrode during the process of electrolysis is directly proportional to the quantum of electricity that can pass through that electrolyte and the weight of a variety of substances that will be formed by passing the same quantity of electricity shall be proportional to the respective weight of the given substances.

The Outcome of an Electrolysis Reaction

When an electrolysis takes place, there are some primary factors that are the determining factors about whether or not complete electrolysis will take place. Sometimes, an excess of voltage is needed to overcome the surface interaction at the electrodes. This phenomenon is more prevalent in the case of gases. Sometimes, more than one-half reactions could be taking place during the electrolysis.

This means that there are more than two possibilities for cell reaction. A given inert electrode’s ability to undergo electrolysis reaction will depend on the present reactants in the electrolyte solution while at the same time, an active electrode is capable of running on its own to perform the oxidation or reduction half-reaction in the solution. These theories can help in predicting the outcome or the expected result of an electrolysis reaction conveniently.

Solved Examples for You

Question: How does aluminium react to the process of electrolysis?

Solution: Aluminium can be most easily found in most rocks. It is one of the most abundantly found in the crust of the earth. However, isolation of the metal from impurities and other metals proves to be a very costly affair. This is the reason why separation of aluminium through electrolysis is very difficult to achieve. This is because, in the stated reaction, it would be water which would get electrolyzed in preference to aluminium itself.

Reducing Aluminium from its Fluoride Salts by Electrolysis

However, in the year 1886, scientists Charles Hall and Paul Herault developed a practical way. Their method was aimed at achieving electrolysis of the metal in an economic manner. The apparatus includes a carbon cathode and a carbon anode and a crust of frozen electrolyte. Carbon anode is a device that could lower the anode as it gets consumed.