Concentration cells are a type of galvanic cell that comprises two equivalent half-cells with the same concentration. Reduction in thermal free energy will lead to the generation of electricity in concentration cells. Electrochemistry occurs in the concentration of cells. Apart from two major types of cells, there are metal-ion concentration cells, oxygen concentration cells and active-passive cells.
Corrosion can occur in concentrated cells. It is due to the metal that is being used in contact with various concentrations, which in turn causes the metal to possess different electrode potentials compared to other parts. Oxygen is one of the elements that is associated with corrosion.
Types of Concentration Cells
Electrolyte Concentration Cells
The electrolyte concentration cell comprises two same electrodes that are dipped in an electrolyte, which possesses different concentration levels. An electrolyte has a tendency to diffuse from a solution of a higher concentration level to a solution of a lower concentration level. With a period of time, the two concentrations tend to be equal.
Electrode Concentration Cells
Electrode concentration cells consist of two cells where identical electrodes are dipped in the same solution with different levels of concentration. For instance, consider two hydrogen electrodes that are placed at a different gaseous pressure in the same solution consisting of hydrogen ions.
Uses of Concentration Cells
The acidity-basicity of a specific solution is determined by a pH metre. This method is adopted for a particular type of cell that is used as an arrangement for a concentration cell. It primarily consists of a voltmeter and an electrode. The first electrode comprises a silver chloride (metal wire) and a part of glass which is semi-porous. It is filled with potassium chloride surrounded by silver chloride and is kept at a pH value of 7.
The second electrode is termed a reference electrode. It comprises a potassium chloride solution surrounded by a potassium wire. The main role of the second electrode is to enact a comparison for a solution that is to be tested. An electric potential is created whenever a glass electrode comes in contact with different pH levels. It is mainly caused due to the reaction that occurs between hydrogen and metal ions.
Now, the voltmeter that is connected to the electrode is used to measure the potential. The higher the voltage, the more acidic is the solution, resulting in more hydrogen ions in the solution. An example of a pH metre is illustrated below.