Nernst equation of battery electromotive force

The value of the electrode potential or the electromotive force of the battery is not only determined by the nature of the material constituting the electrode, but also related to factors such as the concentration of each substance in the electrode or battery, the pressure of the gas, the pH of the medium, and the temperature of the reaction
.

1.
The Nernst equation of battery electromotive force

For battery reaction

aA(aq)+bB(aq)=gG(aq)+hH(aq)

Satisfy the chemical reaction isotherm

△ _r Gm=△ _r Gm ^Θ +RTInQ ^Θ

Substituting △ _r Gm=-zFE and △ _r Gm ^Θ =-zFE ^Θ into the chemical reaction isotherm formula, there is

-zFE=-zFE ^Θ +RTInQ ^Θ

Organize, get

Change the bottom, get

298K hours

This is the Nernst equation of battery electromotive force
.

2.

React the battery

aA(aq)+bB(aq)=gG(aq)+hH(aq)

Decomposed into two electrode reactions, the positive electrode A is oxidized and G is reduced, then the electrode reaction is

aA+ze-=gG

The negative electrode H is oxidation type and B is reduction type, then the electrode reaction is

ZE + hH ^- = bB

The Nernst equation of the battery electromotive force of the battery reaction is

Rewrite the above formula as

Put the positive and negative data together, and get

The two electrodes are independent, corresponding to

Therefore, for any electrode reaction, there is a general relationship

This is the Nernst equation of electrode potential, which reflects the relationship between non-standard electrode potential and standard electrode potential at a certain temperature, that is, reflects the influence of concentration on electrode potential
.

Using the Nernst equation of electrode potential, you can start from the standard electrode potential value to calculate the electrode potential value in any state, and you can also calculate the standard electrode potential value based on the electrode potential value in a certain state
.

When using the Nernst equation of electrode potential, it should be noted that the oxidation type in the formula refers to all substances on the oxidized side of the electrode reaction, and the reduced type refers to all substances on the reduced side of the electrode reaction
.

Of MnO _.

The Nernst equation is

In this reaction, the electrode, in addition to oxidized of MnO _.

Another example, the electrode reaction at 298K

Cl ₂ + 2E ^- = 2Cl ^-

The Nernst equation is