[dudebuddyguy]

So I'm onto the next part of my online coursework, which is Galvanic cells, and I see this:

2. Create a Daniell cell given the following cell notation:

Pb/Pb(NO3)2//Ca/Ca(NO3)2

a)   Label the electrolytes, electrodes, internal circuit, external circuit, salt bridge(choose an appropriate salt).

b)   Write the oxidation half-reaction, the reduction half-reaction, and the redox reaction equation

c)   Show the direction of electron flow.

d)   Show the direction of movement of the sodium cations and chloride anions.

e)   Determine the cell potential.

f)   Which electrode will decrease in mass as the reaction proceeds?

So I started out by doing the redox reaction, and here's what I got:

Pb = 2 e + Pb{+2}N{+5}O3{-6}
Ca = 2 e + Ca{+2}N{+5}O3{-6}

Judging by some videos I've watched, the redox reaction involves adding either H⁺'s or H₂O to either side to balance it out. With the two reactions above, it seems that I'd need to add 12H⁺ to both sides to balance them out, which means that both sides are reduction reactions, and there's no oxidation reaction.

Now, when I move onto the other parts of this question, it looks to me like there won't be any reaction or flow of electrons in the Galvanic Cell. Why does this all seem wrong to me?

I mean, the E⁰(V) of Pb and Ca are -0.13 for Pb, and -2.87 for Ca, so there is a difference in voltage, but other than that, something just seems kinda wrong to me about this equation.

[Borek]

NO₃^- is just a spectator and doesn't change during the reaction. However, metal comes in two forms and getting from to other requires either oxidation or reduction.

Are you sure it was about calcium? Not Co or Cd?

[dudebuddyguy]

NO₃^- is just a spectator and doesn't change during the reaction. However, metal comes in two forms and getting from to other requires either oxidation or reduction.

Are you sure it was about calcium? Not Co or Cd?

Yep, it was Calcium. That's the other bit I found weird. I mean, this is an "adult learning" program provided by a local Catholic district school board, so the majority of the provided information has references to God in it, and I have seen quite a few spelling/grammatical errors, so it doesn't surprise me that there's a potential error in this question.

[Borek]

Technically it is not impossible to use calcium, it is just quite challenging to find a solvent. As these reactions typically take place in water, calcium is never used as an example, as it will react with water, not with the other metal.

For the same reason you typically never see any 1^st nor 2^nd group metals in such questions.

[dudebuddyguy]

Technically it is not impossible to use calcium, it is just quite challenging to find a solvent. As these reactions typically take place in water, calcium is never used as an example, as it will react with water, not with the other metal.

For the same reason you typically never see any 1^st nor 2^nd group metals in such questions.

Odd. Well I did email the teacher for the course to ask if that formula was written correctly, as both formulas came out to be Reduction Half-Reactions, which would mean the Galvanic Cell has two cathodes and no anodes.

I've since skipped past the Electrochemistry section (which was just this assignment, then a test that I had to email the teacher to obtain a copy of) into the next section which is Organic Chemistry, and starts out with some real simple stuff; Lewis Structures.

So I'm a happy student now, getting back to the easy stuff.

[Borek]

Odd. Well I did email the teacher for the course to ask if that formula was written correctly, as both formulas came out to be Reduction Half-Reactions, which would mean the Galvanic Cell has two cathodes and no anodes.

This is a non issue. We are talking about reversible reactions that can go both ways. Just like you can oxidize Pb to Pb²⁺, you can also reduce Pb²⁺ to Pb. Reactions are written as reduction (or oxidation) because of a convention, it doesn't mean that's the reaction direction in a particular system.