I had trouble understanding the explanations for 39 and 32 on the Physical Science Section Test 2, because it seemed like they contradict each other, but I don't know if that's because 32 regards a galvanic cell and 39 is about an electrolytic cell? Anyway, I understood the explanation for 32 to be saying that the EMF would increase since more electrons are flowing and the reaction rate is increasing. But then the explanation for 39 says that doubling the rate at which electrons are produced will not affect the potential difference.
Thanks!
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Ultimately, these two questions boil down to thinking about voltage. You can think of voltage as how intense the draw is on each electron, sort of like a force. Voltage itselfisn't a force, but it's an analogy that helps explain these two questions.
In the case of question 32, when we increase the concentrations of our reactants, that means that we'll have our reactions at our cathodes and anodes happening more often, or at a faster rate. Thus, at any given time, we start building up even more attractive force for the electrons at our cathode, and even more repulsive force from our anode. That is, our anode gets more negatively-charged and our cathode more positively-charged at any given time, since the reaction is going quicker. This means that we've increased the "force" or voltage on our electrons.
In 39, however, we haven't actually changed the effect on any given electron. Yes, we have more flowing, but each one experiences the same pull it did as when we have the original current. With the same "pull" as before, we have the same voltage.
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