galvanic cell

[SilvrGrey330]

I came across this kaplan question:

In a galvanic cell, which of the following statements is true?

a) Anions move to anode, and e- flow from anode to cathode
b) Anions move to anode, and e- move from cathode to anode
c) Anions move to cathode, and e- move from anode to cathode
e) Anions move to cathode, and e- move from cathode to anode

I picked A...because this is what i learned from Princeston review material. That, Anode is - terminal in a galvanic cell, its where oxidation occurs, (the loss of electrons) and therefore electrons flow from anode to cathode, and since it is building up a + charge, the ANIONS from the salt bridge (lets say salt bridge has KNO3, then K+ and NO3- is the salt ions) and the anion of the two, bring NO3- will migrate to the ANODE, to neutralize the building up + charge in the oxidation beaker.

Am i right? or is Kaplan correct. They saying the ANSWER is C, their logic is anion, is - and attracted to cathode the + electrode. I understand + atracts - and vice versa, but read my reasoning above.

Can someone explain...is the answer perhaps A? btw this is a Discrete question.

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[danielle53181]

I came across this kaplan question:

In a galvanic cell, which of the following statements is true?

a) Anions move to anode, and e- flow from anode to cathode
b) Anions move to anode, and e- move from cathode to anode
c) Anions move to cathode, and e- move from anode to cathode
e) Anions move to cathode, and e- move from cathode to anode

I picked A...because this is what i learned from Princeston review material. That, Anode is - terminal in a galvanic cell, its where oxidation occurs, (the loss of electrons) and therefore electrons flow from anode to cathode, and since it is building up a + charge, the ANIONS from the salt bridge (lets say salt bridge has KNO3, then K+ and NO3- is the salt ions) and the anion of the two, bring NO3- will migrate to the ANODE, to neutralize the building up + charge in the oxidation beaker.

Am i right? or is Kaplan correct. They saying the ANSWER is C, their logic is anion, is - and attracted to cathode the + electrode. I understand + atracts - and vice versa, but read my reasoning above.

Can someone explain...is the answer perhaps A? btw this is a Discrete question.

Hmmm...I agree anions should move toward anode due to the buildup of positive charge because of the constant oxidation occurring. Anyone else?

 

[Overeducated]

I picked A...because this is what i learned from Princeston review material. That, Anode is - terminal in a galvanic cell, its where oxidation occurs, (the loss of electrons) and therefore electrons flow from anode to cathode, and since it is building up a + charge, the ANIONS from the salt bridge (lets say salt bridge has KNO3, then K+ and NO3- is the salt ions) and the anion of the two, bring NO3- will migrate to the ANODE, to neutralize the building up + charge in the oxidation beaker.

I would have to agree with (A) for the same reasons you gave

 

[SailCrazy]

It sounds to me like you're right.

I happen to have my Raymong Chang Chemistry book handy, and here's what he has to say:

"During the course of the overall redox reacion, electrions flow externally from the anode... throug the wire and voltmeter to the cathoide... In solution, the cations... move toward the cathode, while the anions... move toward the anode. Without the sald bridge connecting the two solutions, the buildup of positive charde in the anode compartment (due to the formation of... +ions) and negative charge in the cathode compartment (created when some of the ...+ iond are reduced...) would quickly prevent the cell from operating."

 

[cfdavid]

A is correct. The salt bridge has to balance the charge in the respective solutions.

 

[gluon999]

Anode is - terminal in a galvanic cell

isn't anode always the positive terminal?

 

[Prophecies]

isn't anode always the positive terminal?

In a galvanic cell, the anode is negative; in an electrolytic cell, the anode is positive.

 

[SilvrGrey330]

thanks guys, appreciate it

 

[Mikhail]

What is the correct answer in Kaplan?
Personally, I would answer C. I don't think test writers want you to think so hard. You have a negatively charged ion that should move toward positive metal. So, an anion would move toward a cathode. But I may be wrong.

Good luck!
Mikhail

 

[SailCrazy]

My initial reaction reaction was also C, but then as I thought about it a bit - and looked it up, I'm pretty solid on A.

I was trying to point out that the basic one-paragraph definition would say that A is the answer. I think it is supposed to be a question about basic facts of galvanic cells, not a difficult concept to really think about too much.

If the cations and anions moved as answer C says, the cell would cease to function.

What is the correct answer in Kaplan?
Personally, I would answer C. I don't think test writers want you to think so hard. You have a negatively charged ion that should move toward positive metal. So, an anion would move toward a cathode. But I may be wrong.

Good luck!
Mikhail

 

[QofQuimica]

I came across this kaplan question:

In a galvanic cell, which of the following statements is true?

a) Anions move to anode, and e- flow from anode to cathode
b) Anions move to anode, and e- move from cathode to anode
c) Anions move to cathode, and e- move from anode to cathode
e) Anions move to cathode, and e- move from cathode to anode

I picked A...because this is what i learned from Princeston review material. That, Anode is - terminal in a galvanic cell, its where oxidation occurs, (the loss of electrons) and therefore electrons flow from anode to cathode, and since it is building up a + charge, the ANIONS from the salt bridge (lets say salt bridge has KNO3, then K+ and NO3- is the salt ions) and the anion of the two, bring NO3- will migrate to the ANODE, to neutralize the building up + charge in the oxidation beaker.

Am i right? or is Kaplan correct. They saying the ANSWER is C, their logic is anion, is - and attracted to cathode the + electrode. I understand + atracts - and vice versa, but read my reasoning above.

Can someone explain...is the answer perhaps A? btw this is a Discrete question.

I think this is a piss-poor question; none of the answer choices is really right. Everyone who said that the anions have to move into the anode half-cell to replace the lost electrons is correct. But, the question asked about the electrode, not the oxidation half-cell as a whole. The anions (nitrates) won't actually go to the anode itself, which is indeed negatively charged in a galvanic cell. The anode is dissolving; when that happens, the positive metal ions from it will be countered in solution by the nitrate ions from the salt bridge. So the best answer is that the anions go to the oxidation half-cell solution, not to either electrode. But out of the available choices, C is the best for the reason that they gave. How's that? Clear as mud???

 

[danielle53181]

I think this is a piss-poor question; none of the answer choices is really right. Everyone who said that the anions have to move into the anode half-cell to replace the lost electrons is correct. But, the question asked about the electrode, not the oxidation half-cell as a whole. The anions (nitrates) won't actually go to the anode itself, which is indeed negatively charged in a galvanic cell. The anode is dissolving; when that happens, the positive metal ions from it will be countered in solution by the nitrate ions from the salt bridge. So the best answer is that the anions go to the oxidation half-cell solution, not to either electrode. But out of the available choices, C is the best for the reason that they gave. How's that? Clear as mud???

I think you meant A...C says they go to the cathode (or, the way you would correctly prefer it to be defined, they meant the reduction half-cell solution in C)...however, at this point all has been lost and I am defeated...ok, by all I meant one question discussed on an MCAT discussion board

 

[danielle53181]

I think you meant A...C says they go to the cathode (or, the way you would correctly prefer it to be defined, they meant the reduction half-cell solution in C)...however, at this point all has been lost and I am defeated...ok, by all I meant one question discussed on an MCAT discussion board

Nevermind...I think you were trying to imply the actual attraction to the charge on the electrode and that is why it is C...a very bad question

 

[QofQuimica]

Nevermind...I think you were trying to imply the actual attraction to the charge on the electrode and that is why it is C...a very bad question

yes

 

[SilvrGrey330]

ok...

So, we've established:

1) This is a badly worded question
2) If its just talking about the soln of the beakers (or 2 half cells) then C is correct, and not taking into acount the salt bridge. Because at the Anode, electrons willl leave, there will be Cations formed, and they will be attracted to the (-) anode electrode.
3) If we DID include a salt bridge as our though process, then A would be correct. Because the ANION from the salt bridge will Counteract the building up + charge in the oxidation beaker.

A and C are correct, depending on which senario one is looking at.

But we can all agree, this is BAD question for a DISCRETE?

 

[cfdavid]

Yes, piss poor question. But, now I know why they are suggesting C. It's a matter of perspective, though when we tend to think of anions and cations "moving", we automatically assume it's those in the salt bridge, and not what the anions and cations are inclined to do in the actual solution of the half cell.

I guarantee there will be bulls.it, ambiguous questions like that on the MCAT, and of course some will get them right and some will get them wrong. But, it doesn't prove what we actually know based upon "content typically covered in first year science courses". Just venting here.