Name: Gibbs Free Energy, EMF and Equilibrium Constant
Uploaded: 2019-07-19
Duration: 6 min 15 s
Description: There are various thermodynamic parameters that are to be considered while studying the working of an electrochemical cell. Let's learn about them here!

Question

What is Nernst equation? Explain the significance of various terms used.

Accepted Answer

The Nernst Equation the determination of cell potential under non-standard conditions. It relates the measured cell potential to the reaction quotient and allows the accurate determination of equilibrium constants (including solubility constants).

In electrochemistry, it is equation that relates the reduction potential of an electrochemical reaction (half cell or overall reaction) to the standard electrode potential, temperature, and activities (often approximated by concentrations) of the chemical species undergoing reduction and oxidation. It is the most important equation in the field of electrochemistry. It was named after Walter Nernst a German physical chemist who formulated the equation.

When the cell potential equals zero, the reaction is at equilibrium.and E_cell =0

Nernst Equation- It is used to find the cell potential at any moment in during a reaction or at conditions other than standard-state.The various forms of this equation can be as follows.

E = cell potential (V) under specific conditions

E°= cell potential at standard-state conditions

R = ideal gas constant = 8.314 J/mol-K

T = temperature (kelvin), which is generally 25°C (298 K)

n = number of moles of electrons transferred in the balanced redox couple equation

F = Faraday's constant, the charge on a mole of electrons = 95,484.56 C/mol

lnQc= the natural log of the reaction quotient at the moment in time=

$E_{cell}^{\circ} = \frac{RT}{nF} lnK E_{cell}^{\circ} = 0.0257 Vn lnK = 0.0592 Vn logK (at 298.15 K) E_{cell} = E_{cell}^{\circ} - RT / nF lnQ (Nernst equation) E_{cell} = E_{cell}^{\circ} - 0.0257 Vn lnQ = 0.0592 Vn logQ (at 298.15 K) ΔG = - {nFE}_{cell} {ΔG}^{\circ} = - nF E_{cell}^{\circ} w_{ele} = w_{\max} = - {nFE}_{cell} .$

What is Nernst equation? Explain the significance of various terms used.

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