concentration cells

[Dina Marchenko 2J]

Why does a difference in concentrations cause a flow of electrons? And why do the electrons flow from low concentration to high concentration? Is there still a redox reaction taking place? Or is it something else?

[Rory Simpson 2F]

In concentration cells, the same half reaction is occurring but in opposite directions. For the lower concentration, the half reaction would be increasing the amount of the species in solution, while the half reaction for the higher concentration would decreased the amount. The transfer of electrons results from the potential difference created as the species tries to reach equilibrium.

[Naji Sarsam 1F]

To clarify, the reaction is still considered a redox reaction. However, it is also important to note that the standard cell potential of every concentration cell equals 0.

[Naneeta Desar 1K]

In concentration cells the E°cell is always 0.

[Manav Govil 1B]

You will need to use the Nernst equation for most concentration cell questions, especially for finding Ecell or a concentration of a half-cell. Just like the comment before this one says, E°cell = 0, and we have to apply this information to get more information.

[Mulin_Li_2J]

The concentration causes electron flow because Ecell is concentration-dependent, whose value can be calculated with the Nernst equation, Ecell = E*cell - (RT/nF)lnQ. In a concentration cell, E*cell equals 0 because anode and cathode have the same redox couples, and therefore same E* value under standard conditions. Thus, we can rewrite this equation as Ecell = - (RT/nF)lnQ.

Think of Le Chatlier's principle, to reach chemical equilibrium, the low concentration electrode wants to dissociate more ions. In the process of producing ions, electrons are released and transferred to the other electrode, forming a current. Thus, electrons flow from low concentration to high concentration.

Hope this can help!