Multiple Choice
Calculate the maximum obtainable work in kJ for the balanced redox reaction below at 25 °C. Given: 3 MnO4–(aq) + 4 H+(aq) + 5 NO(g) --> 3 Mn2+(aq) + 2 H2O(l) + 5 NO3–(aq), E°cell = 0.540 V. (HINT: 1 V = 1 J/C)
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20. Electrochemistry
Cell Potential and Gibbs Free Energy
Multiple Choice
For a large negative E°cell, what values of the equilibrium constant (K) and Gibbs free energy change (ΔG) are expected?
A
K < 1 and ΔG > 0
B
K = 1 and ΔG = 0
C
K > 1 and ΔG < 0
D
K > 1 and ΔG > 0
Verified step by step guidance1
Understand the relationship between E°cell, the equilibrium constant (K), and Gibbs free energy change (ΔG). The standard cell potential (E°cell) is related to the spontaneity of a reaction.
Recall the Nernst equation, which relates E°cell to the equilibrium constant (K): . A large negative E°cell suggests a non-spontaneous reaction, indicating a small K value.
Consider the Gibbs free energy equation: . A large negative E°cell results in a positive ΔG, indicating a non-spontaneous process.
Analyze the implications: A large negative E°cell means the reaction is not favorable under standard conditions, leading to K < 1 and ΔG > 0.
Conclude that for a large negative E°cell, the equilibrium constant (K) is less than 1, and the Gibbs free energy change (ΔG) is greater than 0, confirming the non-spontaneity of the reaction.
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