Why does a mercury cell deliver a constant voltage for its entire life ?
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Solution and Explanation
Explanation: In a mercury cell, the overall reaction involves only solids and ions whose concentrations remain essentially constant throughout the life of the cell. Since the concentration terms remain unchanged, the reaction quotient \(Q\) remains constant. According to the Nernst equation, \[ E_{cell} = E^\circ_{cell} - \frac{0.0591}{n}\log Q \] Since \(Q\) remains nearly constant, the cell potential remains practically unchanged. Therefore, a mercury cell supplies a steady and constant voltage until almost all reactants are consumed.
Final Answer \[ \boxed{ \text{A mercury cell delivers constant voltage because the concentrations of} \\ \text{reactants and products remain essentially constant during operation.} } \]
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