Electrolysis And Electroplating

What is Electrolysis?

The word “electrolysis” was introduced by Michael Faraday in the 19th century. In chemistry, electrolysis is a method that uses a DC to drive a non-spontaneous chemical reaction. This technique is commercially significant as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell.

We can define electrolysis as:

The process by which ionic substances are decomposed into simpler substances when an electric current is passed through them.

Electrolysis Process:

The fundamental process of electrolysis is the interchanging of ions and atoms by the addition or removal of electrons from the external circuit.

Electrolysis Process

Electrolysis Process

  • Ionic compounds contain charged particles called ions. For example, Sodium Chloride contains positively charged Sodium ions and negatively charged Chlorine ions.
  • The ions must be free to move in order to start the electrolysis process. When an ionic substance is dissolved in water or melted then the ions are free to move. During electrolysis, positively charged ions move to the negative electrode and negatively charged ions move to the positive electrode. Then positively charged ions receive electrons and negatively charged ions lose electrons. Both the products of the dissociation get collected at the electrodes.
  • For instance, if electricity is passed through molten sodium chloride, the sodium chloride is broken into sodium and chlorine and they collect at their respective electrodes. The metals get precipitated and the gases escape. This ability to break down substance with a current is used in many ways.
  • Electrolysis is widely used for Electroplating.

Implementation of Electrolysis:

In medieval times, aluminium was almost as precious as silver. Its extraction was not known and pure aluminium was extremely hard to come by. The application of electrolysis turned aluminium from a precious metal to one of the most largely used metals by humans. Aluminium is extracted from its ore by the process of electrolytic decomposition and deposition.

Uses of Electrolysis

  • Electrolysis is done for coating one metal on another.
  • The industrial use includes various metals such as aluminium, magnesium, chlorine, and fluorine etc.

 

What is Electroplating?

Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.

  • Electroplating is a process that uses electric current to reduce dissolved metal ions by the use of electrolysis, to obtain the dissolved metal ions at the other electrode, mostly in the form of a uniform coating.
  • It is the process of plating one metal onto another by hydrolysis, most commonly for decorative purposes or to prevent corrosion of metals.
  • There are also specific types of electroplating such as copper plating, silver plating, and gold plating. It allows the manufacturers to make the product with economical materials and then coat the metals to add properties such as rust proofing, improving its appearance and improving its strength.

How does Electroplating work?

The positive electrode should be the metal that you want to coat the object with. The negative electrode will be the object that should receive the deposit of the electroplating metal. The electrolyte should be a solution of the coating metal, as it is a metal nitrate or sulphate. We can examine this better with few examples;

Silver Plating:

Silver Plating

Silver Plating

The object that is to be plated is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is a silver nitrate solution. This process can also be used to purify silver. We can take an impure block at the positive terminal and a strip of pure silver to the negative. The pure silver is deposited via electrolysis at the negative terminal leaving behind the impurities.

Copper Plating:

Copper Plating

Copper Plating

The object that is to be plated is connected to the negative terminal of the power supply. A piece of copper is connected to the positive terminal. The electrolyte is copper Sulphate solution.

Like with silver plating, copper deposition can be used to purify copper. In this case, both the electrodes are made from copper. As the impure positive electrode gradually disappears leaving the impurities behind the negative electrode gradually gets coated with pure copper.

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Practise This Question

Rohit has an impure copper plate and wants to purify it by electroplating. Using an electrolytic setup, he can do this by 

 

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