8 posts • Page 1 of 1
A concentration cell is a cell that is has two half-cells with the same electrodes, but with different concentrations. The voltage difference is created by electron transfer from the cell with the lower concentration to the cell with the higher concentration. An example for this could be a cell where the anode consists of Zn/Zn2+(0.5M) whereas the cathode consists of Zn2+(0.02M)/Zn.
A concentration cell occurs when the anode and the cathode both have the same electrodes but with different concentrations. This would mean that the voltage difference would be created by the different concentrations rather than different cathodes.
A concentration essentially uses the -(RT/nF)lnQ term of the Nernst Equation to generate (a small amount) of electricity. Since the half reactions at the cathode and anode are the same, the standard cell potential is zero. Therefore, the difference in concentration (i.e. Q) makes the overall cell potential positive.
Like everybody else is saying, a concentration cell just happens when both the anode and cathode have the same electrodes in it but with different concentrations. The most important thing to remember for concentration cells though is that E standard cell is equal to 0.
If a concentration cell has the same concentration on the anode and cathode then the reaction is at equilibrium and there is no net transfer of electrons in either direction. If this happens in a battery it means that the battery is dead.
Who is online
Users browsing this forum: No registered users and 1 guest