What is nernst equation?

The Nernst Equation is a formula used in electrochemistry to determine the [Equilibrium%20Electrode%20Potential] of a cell or a single electrode at any given temperature, pressure, and concentration. It relates the reduction potential of an electrochemical reaction to the standard electrode potential, temperature, and activities (or concentrations) of the oxidized and reduced species.

Here's a breakdown of key aspects:

• Purpose: Calculates the actual [Electrode%20Potential] under non-standard conditions. Standard conditions are typically 298 K (25°C), 1 atm pressure (for gases), and 1 M concentration (for solutions).

• Formula: The general form of the Nernst Equation is:

  E = E° - (RT/nF) * ln(Q)

  Where:

  • E = Cell potential under non-standard conditions
  • E° = [Standard%20Cell%20Potential]
  • R = Ideal gas constant (8.314 J/(mol·K))
  • T = Temperature (in Kelvin)
  • n = Number of moles of electrons transferred in the cell reaction
  • F = Faraday's constant (96485 C/mol)
  • Q = Reaction quotient

• Reaction Quotient (Q): Represents the ratio of products to reactants at a given point in time, considering their activities (or concentrations). It indicates the relative amount of reactants and products and determines the direction the reversible reaction must shift to reach equilibrium. For a general reaction aA + bB ⇌ cC + dD, Q = ([C]^c[D]^d) / ([A]^a[B]^b)

• Simplified Form (at 298 K): Often, the Nernst equation is simplified for calculations at 25°C (298 K) using base-10 logarithms:

  E = E° - (0.0592/n) * log(Q) (where 0.0592 V is the value of (2.303RT/F) at 298 K).

• Applications:

  • Calculating cell potentials in electrochemical cells (batteries, fuel cells).
  • Determining the pH of a solution using a hydrogen electrode.
  • Measuring ion concentrations using ion-selective electrodes.
  • Understanding corrosion processes.

• Limitations:

  • The Nernst equation assumes ideal behavior of solutions. In reality, deviations from ideality can occur, especially at high concentrations. Activity coefficients are used to account for non-ideal behavior.
  • It does not apply to systems far from equilibrium.
  • It only considers the thermodynamics of the reaction and does not provide information about the kinetics (rate) of the reaction.