Question

What factors affect electrochemical cells?

Answer 1

The Gibbs free energy change determines the voltage of an electrochemical cell. This in turn depends on factors such as concentration, gas pressure, and temperature.

Explanation:

Gibbs Free Energy

The Gibbs free energy measures how far a system is from equilibrium.

It therefore determines the voltage (driving force) of an electrochemical cell.

`ΔG = -nFE` or `E = -(ΔG)/(nF)`

where `n` is the number of moles of electrons transferred and `F` is the Faraday Constant.

Concentration and Gas Pressure

`ΔG = ΔG° - RTlnQ`, where `Q` is the reaction quotient.

For an equilibrium reaction such as `"A" ⇌ "B + C"`,

`Q =(["B"]["C"])/(["A"])` or `Q = (P_"B" P_"C")/P_"A"` if the substances are gases.

`E` depends on `ΔG`, `ΔG` depends on `Q`, and `Q` depends on concentration and pressure.

Therefore both concentration and gas pressure affect the voltage of the cell.

Temperature

According to the Nernst Equation,

`E = E° - ((RT)/(nF))lnQ`

The temperature term in this equation shows that temperature also affects the cell voltage.