Types of Concentration Cells

Concentration cell is an interesting concept in chemistry that uses substances to produce voltage. The concept derives its name from the difference in the concentration of the solution. We will explain more about the method and usage of concentration cells in this article. This article also answers some frequently asked concentration cell questions at the end. 

What is a concentration cell?

A concentration cell is a galvanic cell that comprises two half-cells filled with the same electrodes. However, the concentration of the substance varies in those two half-cells, one being a low concentrated cell and the other being a high concentration cell. 

Another name of the concentration cell is electrochemical cell because it can produce electrical energy. The movement of the substance from the high concentration cell to the low concentration cell produces electrical power. However, the energy produced by the cell is often less than 60 millivolts; hence it is not used to store energy. 

The two half-cells with different concentrations always tend to balance the substance in the cells. Hence, the cell with a high concentration is diluted to increase substances in the cell with low concentration. This method is called chemical equilibrium. 

What are the types of concentration cells?

A concentration cell is classified mainly into two types, such as 

• Electrolyte concentration cell

• Electrode concentration cell

You will know what these terms stand for in these concentration cell notes. 

• Electrolyte concentration cell

In this type of cell, two same electrodes are dipped in a solution made of electrolyte, which has different concentration levels. This cell type moves electrodes from the higher concentration to the lower concentrated solution to form a balance. 

For instance, an electrolytic concentration cell consists of hydrogen and oxygen ion. The cell is used to decompose water. 

• Electrode concentration cell

Electrode cell consists of the same electrodes dipped in a solution made of the same electrodes, and however, the concentration of those electrodes is different. 

For example, two hydrogen electrodes exposed to different gaseous pressure are dipped in a solution. This solution is also made of hydrogen ions but is placed at different concentrations in the half-cells.  

Electrolyte and electrode concentration cells are the two main types of concentration cells. However, there are other types of cells as well. In the next section of concentration cell notes, we will know about the other cells.

What are the other types of the cell?

Besides the two primary cells, electrolyte and electrode, there are three other cells. Those are

• Metal-ion concentration cell
• Oxygen concentration cell
• Active Passive concentration cell 

Let us know what these terms mean.

• Metal-ion concentration cell

In this cell, a solution of metal ions placed at a high concentration will exist on faying surfaces in the presence of water. On the other hand, metal ions with low concentrations will be at the aperture of the cell. 

The higher concentrated metal ions will be anodic, and the lower concentration metal ions will be cathodic. The former one is protected, and the latter is corroded. 

• Oxygen concentration cell

In an oxygen cell, the oxygen in the air will be restricted from diffusing uniformly into the water solution. The water already contains dissolved oxygen as it touches the metal surface, creating a difference in oxygen concentration in the two half-cells. 

• Active Passive concentration cell

In this type of concentration cell, the metal substance relies on an ultra-bonded passive film to protect it from corrosion. The passive film is usually an oxide. Here the salt accumulates in the surface of the metal to break the film in the presence of water. 

The electrical energy in the cell will develop between the passive film and the exposed active metal. Here the former will play the role of a cathode, and the latter will be the anode of the concentration. 

What are the uses of concentration cells?

A concentration cell is a galvanic cell, which means it comes under the electrochemical cells. These cells are used to provide electrical energy in batteries. Energy is produced when electrons move into the cathode and out of the anode. The use of electrochemistry is significant in our lives. It provides power to many electrical appliances that work on batteries. An electrochemical cell is a standard 1.5-volt cell that is used in

•  TV remotes
• clocks
• calculators
• flashlight
• automobile
• phones

These are the most common uses of a concentration cell or electrochemical cell. Many appliances or batteries use one or more such cells to operate. 

Electrochemistry is also used to plate objects on decorative metals such as gold or chromium. 

What are the components of a concentration cell?

A concentration cell is built with three components. Those are salt bridge, electrode and voltmeter. 

• Salt bridge

It separates two half-cells and makes way for the exchange of the ions in the solution. Electric wires are skipped in this method because the ions would negatively react to the energy. Also, it would cause the build-up of electrons. 

• Electrode

Electrodes present in the concentration cells are known as cathode and anode. When oxidation occurs, anode loses electrons and passes them to the cathode. Therefore, the electrons pile up in the cathode and start reducing it.

• Voltmeter

The voltmeter is usually kept in between the two half-cells. It is used for measuring the cell potential or the voltage difference created by the increase in the concentration of the reactants. The cell potential is also known as the electromotive force or EMF. 

What is the method used in concentration cells?

A voltage is produced by reducing thermodynamic energy in the concentration cell. This occurs because of the chemical equilibrium in the two half-cells. This energy is also used in reducing or increasing the electrodes in the cells. 

The cells absorb the thermal energy as heat, which leads to the increase of entropy through chemical equilibrium. Similarly, the entropy decrease is compensated when the heat is converted to electrical power. 

Conclusion

Learning about concentration cells is interesting as it has significant usage in our daily lives. Moreover, the students get an idea about the movements of electrolytes in different concentrations. Concentration cells are an important technology used mainly in batteries. The technology is used for the transference of substance to form an equilibrium between the concoctions. Concentration cells are a limited form of galvanic cells. Here energy is produced by moving a substance from the high concentration cell to the low concentration cell. The cell establishes equilibrium inconsistency through this transference of the electrons from one cell to another, called chemical equilibrium. To reach the balance in electrons, the higher concentration cell is diluted, and the other half with less concentration gets increased through this transfer.