Potential, Free, and Equilibrium Flashcards
- Explain the relations between potential, free energy change, and equilibrium constants. - Perform calculations involving the relations between cell potentials, free energy changes, and equilibrium. - Use the Nernst equation to determine cell potentials under nonstandard conditions.
Faraday’s Constant (F)
Represents the electric charge carried by one mole of electrons.
Approximate value: 96,485 Celsius/ Mole
What are the applications with the Faraday Constant?
- Used to calculate electric charge involved in redox reactions.
- Appears in the equation:
ΔG=−nFE
What do each variable represent in:
ΔG=−nFE?
ΔG: Gibbs free energy
n: moles of electrons
E: is cell potential
What is Nernst equation?
Describes how the cell potential changes with the concentration of reactants and products at any condition (not just standard conditions).
What does the variables in the equation represent?
E = Cell potential at non-standard conditions.
E°: Standard cell potential.
R = Gas constant ( 8.3145 J/ Mole x Kelvin)
T = Temperature (in Kelvin)
n = Number of moles of electrons transferred.
F = Faraday’s constant (96,485 Celsius / Mole).
Q = Reaction quotient (ratio of products to reactants).
What is the Nernst equation used for?
- Helps calculate the actual cell potential based on the concentrations of reactants and products.
- It’s useful in predicting how a cell’s voltage changes as reaction conditions vary.
- This equation is important as it is linked to thermodynamics (free energy) with electrochemistry (cell potential), helping explain how chemical reactions proceed under different conditions.
There is a simplified form at 25 degrees Celsius of Nernst equation. What is it?
E = E∘ - 0.0592 / n (log Q)
What are concentration cells?
A type of galvanic cell where the electrodes are the same material, but the concentrations of the solutions differ.
How do concentration cells work?
- Cell potential arises from the difference in concentration between the two half-cells.
- Electrons flow from the side with lower concentration to the side with higher concentration to balance the concentrations.
The NERNST EQUATION helps calculate CONCENTRATION CELLS What is the formula?
E = 0.0592/ n TIMES —>
(log [Higher Concentration] /
[Lower Concentration])
What makes concentration cells different from galvanic cells?
Unlike other galvanic cells, a concentration cell’s potential is driven by concentration differences, not different metals or chemicals.
Applications of concentration cells?
Concentration cells are used to understand electrolyte balance, measure ion concentrations, and in real-world devices like pH meters.
