What is the effect on Ecell when product concentrations increase (assuming other factors fixed)?

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Multiple Choice

What is the effect on Ecell when product concentrations increase (assuming other factors fixed)?

Explanation:
The key idea is the Nernst equation: the cell potential depends on the reaction quotient Q, which reflects the relative amounts of products to reactants. When product concentrations rise while everything else is fixed, Q increases. The Nernst equation says Ecell = E°cell − (RT/nF) ln Q. Since ln Q grows as Q grows, the second term becomes larger, so Ecell decreases. At room temperature this is often written as Ecell = E°cell − (0.0592/n) log Q, making the decrease with increasing Q explicit. This aligns with intuition: adding more products makes the reaction less driven toward doing work in the cell, lowering the observed potential. It won’t become undefined; it simply drops and can approach zero as the system nears equilibrium (Q ≈ K), or become negative if Q exceeds K.

The key idea is the Nernst equation: the cell potential depends on the reaction quotient Q, which reflects the relative amounts of products to reactants. When product concentrations rise while everything else is fixed, Q increases. The Nernst equation says Ecell = E°cell − (RT/nF) ln Q. Since ln Q grows as Q grows, the second term becomes larger, so Ecell decreases. At room temperature this is often written as Ecell = E°cell − (0.0592/n) log Q, making the decrease with increasing Q explicit. This aligns with intuition: adding more products makes the reaction less driven toward doing work in the cell, lowering the observed potential. It won’t become undefined; it simply drops and can approach zero as the system nears equilibrium (Q ≈ K), or become negative if Q exceeds K.

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