All Topics  
Concentration cell

 

 
   Email Print
   Bookmark   Link
 

 

Concentration cell
 
 
  Topics Concentration cell Topic Home

A Concentration cell is an electrochemical cell
Electrochemical cell

An electrochemical cell is a device used for generating an electromotive force and current from electrochemistry, or the reverse, inducing a chemical reaction by a flow of current....
 that has two equivalent half-cells of the same material differing only in concentrations. One can calculate the potential developed by such a cell using the Nernst Equation
Nernst equation

In electrochemistry, the Nernst equation is an equation which can be used to determine the equilibrium reduction potential of a half-cell in an electrochemical cell....
. A concentration cell produces a voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
 as it attempts to reach equilibrium, which will occur when the concentration in both cells are equal.

Concentration cell methods of chemical analysis compare a solution of known concentration with an unknown, determining the concentration of the unknown via the Nernst Equation or comparison tables against a group of standards.

Concentration cell corrosion
Corrosion

Corrosion means the breaking down of essential properties in a material due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen....
 occurs when two or more areas of a metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
 surface are in contact with different concentrations of the same solution.






Discussion
Ask a question about 'Concentration cell'
Start a new discussion about 'Concentration cell'
Answer questions from other users
Full Discussion Forum



Encyclopedia


A Concentration cell is an electrochemical cell
Electrochemical cell

An electrochemical cell is a device used for generating an electromotive force and current from electrochemistry, or the reverse, inducing a chemical reaction by a flow of current....
 that has two equivalent half-cells of the same material differing only in concentrations. One can calculate the potential developed by such a cell using the Nernst Equation
Nernst equation

In electrochemistry, the Nernst equation is an equation which can be used to determine the equilibrium reduction potential of a half-cell in an electrochemical cell....
. A concentration cell produces a voltage
Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
 as it attempts to reach equilibrium, which will occur when the concentration in both cells are equal.

Concentration cell methods of chemical analysis compare a solution of known concentration with an unknown, determining the concentration of the unknown via the Nernst Equation or comparison tables against a group of standards.

Concentration cell corrosion
Corrosion

Corrosion means the breaking down of essential properties in a material due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen....
 occurs when two or more areas of a metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
 surface are in contact with different concentrations of the same solution. There are three general types of concentration cell corrosion:

Metal ion concentration cells

In the presence of water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
, a high concentration of metal ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s will exist under faying
Faying

A faying surface is the surface of a member that is in contact with another member to which it is joined....
 surfaces and a low concentration of metal ions will exist adjacent to the crevice created by the faying surfaces. An electrical potential will exist between the two points. The area of the metal in contact with the high concentration of metal ions will be cathodic and will be protected, and the area of metal in contact with the low metal ion concentration will be anodic and corroded.

Oxygen concentration cells

Water in contact with the metal surface will normally contain dissolved oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
. An oxygen cell can develop at any point where the oxygen in the air is not allowed to diffuse uniformly into the solution, thereby creating a difference in oxygen concentration between two points. Corrosion will occur at the area of low-oxygen concentration which are anodic.

Active-passive cells

For metals that depend on a tightly adhering passive film (usually an oxide
Oxide

An oxide is a chemical compound contaning at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides....
) for corrosion protection, salt
Salt

A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and base . Salts are ionic compounds composed of cations and anions so that the product is electrically electric charge ....
 that deposits on the metal surface in the presence of water, in areas where the passive film is broken, the active metal beneath the film will be exposed to corrosive attack. An electrical potential will develop between the large area of the cathode (passive film) and the small area of the anode (active metal). Rapid pitting of the active metal will result.