Sample interview questions: Describe the behavior of electrochemical cells and their relation to thermodynamics.
Sample answer:
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Electrochemical Cell Behavior:
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Electrochemical cells involve chemical reactions that generate or consume electricity.
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They consist of two electrodes (anode and cathode) immersed in an electrolyte solution.
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Thermodynamics of Electrochemical Cells:
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The driving force for electrochemical reactions is the change in free energy (ΔG) of the system.
- Reactions that release free energy (ΔG < 0) are spontaneous and can generate electricity.
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The maximum amount of electrical work (Wmax) that can be obtained from a cell is equal to −ΔG.
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Cell Potential (E):
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The potential difference between the two electrodes in an electrochemical cell is called the cell potential (E).
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E is directly related to the change in free energy (ΔG): E = −ΔG/nF, where n is the number of moles of electrons transferred and F is the Faraday constant.
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Standard Cell Potential (E°):
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The cell potential under standard conditions (298 K, 1 atm, 1 M concentration) is called the standard cell potential (E°).
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E° is an intrinsic property of the electrochemical reaction and is related to the free energy change: ΔG° = −nFE°.
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Nernst Equation:
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The cell potential (E) at non-standard conditions is given by the Nernst equation:
E = E° − (RT/nF)lnQ, where R is the ideal gas constant, T is the temperature, Q is the reaction quotient, and ln is the natural logarithm. -
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