Electrochemistry

[danny89]

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Question (TPR SW, page 397, question #2): The pH of a fully charged alkaline dry cell must be:
answer: less than the pH of a drained one.
My questions:
The battery gets drained( discharged of its voltage) after time, correct?
Here's my reason: Since the overall reaction in the alkaline dry cell is: (MnO2 + Zn +4H--->Mn +Zn + 2H20), and as the cell operates, it consumes acid (the 4H) When it's consuming acid, the expended, discarged state of the battery has a higher pH than the pH of the charged cell, correct?
Thanks for the help.

 

[sps27]

Question (TPR SW, page 397, question #2): The pH of a fully charged alkaline dry cell must be:
answer: less than the pH of a drained one.
My questions:
The battery gets drained( discharged of its voltage) after time, correct?
Here's my reason: Since the overall reaction in the alkaline dry cell is: (MnO2 + Zn +4H--->Mn +Zn + 2H20), and as the cell operates, it consumes acid (the 4H) When it's consuming acid, the expended, discarged state of the battery has a higher pH than the pH of the charged cell, correct?
Thanks for the help.

I don't have TPR SW with me but by looking at the eqn you have mentioned here is what I think.

The reactants have H and the products don't have it. Now a fully charged alkaline dry cell would mean, no reaction has taken place, which means the reactants are intact i.e., concentration of reactants is more, which would mean more H and hence low pH. A fully discharged alkaline dry cell would mean more products and less reactants and on the product side I don't see any H so I would say, pH is more of fully discharged cell. That is a very simplistic way of looking at things, but that is what come to my mind.