How do you calculate the Nernst equation and its significance?

Sample interview questions: How do you calculate the Nernst equation and its significance?

Sample answer:

Calculating the Nernst Equation:

1. Standard Cell Potential:
2. Begin by determining the standard cell potential (E°), which is the potential of a cell under standard conditions (298 K, 1 atm, and concentrations of 1 M for reactants and products).

3. Standard cell potentials can be found in tabulated data or calculated using the following equation:

   E° = E°(red) - E°(oxid)

   where E°(red) and E°(oxid) are the standard reduction potentials of the reduction and oxidation half-reactions, respectively.

4. Temperature Dependence:

5. The Nernst equation accounts for the temperature dependence of the cell potential through the temperature coefficient, which is related to the change in cell potential with temperature. The temperature coefficient is given by:

   (dE/dT) = -(R * n * F) / T

   where:
   – R is the ideal gas constant (8.314 J/mol·K)
   – n is the number of moles of electrons transferred in the reaction
   – F is the Faraday constant (96,485 C/mol)
   – T is the temperature in Kelvin

6. Concentration Dependence:

7. The Nernst equation also considers the concentration dependence of the cell potential by incorporating the activities of the reactants and products. The activities are related to the concentrations of the species in solution and reflect their effective concentrations in the reaction.

8. Final Equation:

9. The complete Nernst equation is given by:

   E = E° - (R * T / n * F) * ln(Q)

   where:
   – E is the cell potential under non-standard conditions
   – E° is the standard cell potential
   – R is the ideal gas constant
   – T is the temperature in Kelvin
   – n is the number of moles of electrons transferred in the reaction
   – F is the Faraday constant
   – Q is the reaction quotient, which is the ratio of the activities of the products to the activities of the reactants

Significance of the Nernst Equation:

• Predicting Cell Potentials:

• The Nernst equation allows us to calculate the cell potential under non-standard conditions, enabling us to predict the direction and feasibility of redox reactions.

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