EMF question

[km1865]

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So Kaplan says that EMF of an electrochemical cell (voltaic specifically) depends on the number of electrons transferred from the anode to the cathode, I understand that increasing concnetration of reactants will shift the reaction to the right, and it will occur more quickly to the right, and the emf of the cell will increase.. but i'm not so sure how this happens.. i was thinking if the reaction was shifted to the right then more current is being transferred (since current is dQ/dt and t is decreasing since reaction occurs quicker, so current must increase.. but i dont understand why the number of electrons transferred would be affected?) Also, TBR contradicts kaplan here, saying that EMF is independent of the number of electrons transferred (since emf is voltage which is J/C and a coulomb of charge is constant regardless of the number of electrons transferred), rather TBR says that only the free energy is dependent on the number of electrons transferred since dG=-nFE and well n is directly in the equation....

Can anyone clarify these concepts, im a bit confused.. Thanks!

 

[TieuBachHo]

So Kaplan says that EMF of an electrochemical cell (voltaic specifically) depends on the number of electrons transferred from the anode to the cathode, I understand that increasing concnetration of reactants will shift the reaction to the right, and it will occur more quickly to the right, and the emf of the cell will increase.. but i'm not so sure how this happens.. i was thinking if the reaction was shifted to the right then more current is being transferred (since current is dQ/dt and t is decreasing since reaction occurs quicker, so current must increase.. but i dont understand why the number of electrons transferred would be affected?) Also, TBR contradicts kaplan here, saying that EMF is independent of the number of electrons transferred (since emf is voltage which is J/C and a coulomb of charge is constant regardless of the number of electrons transferred), rather TBR says that only the free energy is dependent on the number of electrons transferred since dG=-nFE and well n is directly in the equation....

Can anyone clarify these concepts, im a bit confused.. Thanks!

The voltaic EMF of a cell (or batteries) is measured based on the numbers of accumulated charges separated in an open circuit. So if more charges are being separated due to an addition of reactants, the voltaic EMF of a cell will increase.

The other one stays constant because it measures the voltage that a coulomb of charge would overcome its electric field created by electrical potentials.

For simplicity, I just think of them as BEFORE and AFTER kinda thing.