Explain what happens to battery voltage as a battery is used, in terms of the Nernst equation.

• The Nernst equation specifies the link between cell potential and standard potential, as well as the electrically active (electroactive) species' activities.
• It connects the effective concentrations (activities) of cell reaction components to the standard cell potential.

\(E({\rm{ cell }}) = E({\rm{ cell }},{\rm{ standard }}) - \frac{{0.0592V}}{n} \cdot \log Q\)

• When the battery runs out, it means that its voltage becomes\(\;0\).
• From the Nernst equation, we can conclude that this happens when

\(E({\rm{ cell }},{\rm{ standard }}) = \frac{{0.0592V}}{n} \cdot \log Q\)

\(E({\rm{ cell }},{\rm{ standard }}) = \frac{{0.0592V}}{n} \cdot \log K\)

• We can see that the cell voltage will become zero when the chemical reaction occurring in the battery reaches equilibrium.
• That means that when we turn the battery on, a chemical reaction starts happening and it goes on, like any chemical reaction, until it reaches equilibrium.
• And when it reaches equilibrium, we see from the Nernst equation that the \(E(cell)\) becomes zero, which means that the battery dies when the chemical reaction occurring inside reaches equilibrium.