Electrochemical Series

An electrochemical cell is defined as a device that produces an electric current from the energy released by a spontaneous redox reaction that can be formed by electricity. This type of cells includes the voltaic cells or galvanic cells named after Luigi Galvanic and Alessandro voltas. Both the scientists conducted several experiments on chemical reactions and electric current during the late 18th century.

There are two conductive electrodes in the electrochemical cells: cathode and anode. The electrode where oxidation occurs is known as the anode. Whereas, the cathode is the electrode where the reduction takes place. Electrodes can be made of any sufficiently conductive material such as graphite, semiconductors, metals and even conductive polymers. The electrolyte is in between these electrodes which contain ions which can move freely.

The galvanic cell uses two different metal electrodes. Each has an electrolyte from where the electrode metal gets the positively charged ions and are oxidised. 

Anode will go under oxidation and the cathode is the electrode where reduction reaction takes place. 

A galvanic cell whose electrodes are copper and zinc submerged in copper sulphate and zinc sulfate respectively is known as a daniel cell.

Electrochemistry

Electrochemistry is defined as the branch of physical chemistry which deals with the relationship between the electricity, as a measurable and quantitative phenomenon, and identifiable chemical change. In this, electricity is considered as an outcome of a particular chemical change or vice-versa. These reactions include the electric charges moving between electrolyte and electrode. Therefore, electrochemistry deals with the interactions between chemical and electrical energy. 

When the current is supplied externally to a chemical reaction as in electrolysis or if the electric current is produced by a spontaneous chemical reaction as in a battery, it is called as the electrochemical reaction. In general, we describe the chemical reaction where electrons are transferred directly between atoms or molecules as oxidation reactions. The chemical reaction is the redox reaction, which is the overall reaction when individual redox reactions are separate but connected by an external electrical circuit and an intervening electrolyte.

History

In the 16th century, understanding of electrical matter began. The English scientist named William Gilbert during the 16th century spent 17 years experimenting with magnetism and to lesser extent electricity. Gilbert was known as the father of magnetism for his work on magnetism. He discovered various methods for strengthening magnets and for producing it.

The German physicist Otto Von Guericke in 1663 created the first electric generator which produced static electricity by applying friction in the machine. The generator is made up of a large sulphur ball cast inside the globe of glass mounted on a shaft. By the means of cranks, electric sparks or crank was produced when a pad was rubbed against the ball as it is rotated. The globe can be used or removed as the source for experiment with electricity.

Applications of Electrochemical Series

The electrochemical series’ main applications are listed below:

The Strength of Oxidation and Reduction Strength: The electrochemical series helps to identify the substances that are good reducing and oxidizing agents. All the substances which are appearing on the top of the series behave as good reducing agents and all those substances which are appearing on the bottom of the series are good oxidising agents.

Displacement Reactions: A metal which is higher in the series will replace or displace the metal from its solution which is present lower in the series. The metal which is present or is higher in the series is having a greater tendency to provide electrons to the cations of the metals to be precipitated. The metal which is having low standard potential reduction will displace metal from its salt solution which has a greater value of standard electrode potential.

Predicting the liberation of hydrogen gas by metals from acid, predicting the feasibility of the redox reaction, calculation of EMF of the cells, comparison of the relativity of metals are few of the other areas where the applications of electrochemical series can be seen. 

Characteristics of Electrochemical Series

• In the electrochemical series, all the reduction potentials are given on a hydrogen scale whose Eo is taken as zero. 

• An element’s standard electrode potential is a measure of the tendency of that element to get reduced.

• The element which contains or has the tendency of greater reduction potential gets reduced easily, whereas, the element with low reduction potential gets oxidized easily. Elements which lose electrons easily have low reduction potential and the ones who lose electrons with greater difficulty or instead of losing they accept electrons more easily have a higher reduction potential.

• The higher EMF series elements having a higher reduction potential are placed at the top. The ones having lower reduction potential are placed at the bottom. Standard Hydrogen Electrode (SHE ) acquires the middle position in the electrochemical series.

• The electronegativity of the non-metals decreases as we move down in the electrochemical series.