A particular 12V battery is based on a reaction having a standard cell potential,E° = +1.92 V.What happens when the battery "dies"?
A)E° = 12 V and E = 0 V
B)E° = 0 V and E = 12 V
C)E° = +1.92 V and E = 0 V
D)E° = +1.92 V and E = 12 V

Question

Quizplus · Accepted Answer

When the battery "dies", it means that all the reactants have been converted to products, and the driving force (emf) for the reaction is zero. Therefore, the measured emf of the battery is also zero. However, the standard cell potential E° is a measure of the thermodynamic potential for the reaction based on standard conditions (1M concentration, 298K temperature, 1 atm pressure, etc.), and it does not change during the reaction. In this case, the E° of the battery is given as +1.92 V, which means that under standard conditions, the reaction has a positive emf indicating a spontaneous reaction. Thus, the correct option is C, E° = +1.92 V and E = 0 V.

A Particular 12V Battery Is Based on a Reaction Having