electrochemistry

[chiddler]

In a redox titration, if the voltage in solution rises:
A. Reducing agent must be the titrant
B. Oxidizing agent must be titrant.
C. Titrant can be either.

Answer below.








Answer is C. I'm trying to understand something. Voltage in solution? I thought a voltage occurs only when the two reactions are separated and are connected via metal that enables the redox reaction. Then each cell will have a potential and a voltage can form.

THIS question is suggesting that it all occurs in the same solution. Can a voltage develop?

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[MedPR]

In a redox titration, if the voltage in solution rises:
A. Reducing agent must be the titrant
B. Oxidizing agent must be titrant.
C. Titrant can be either.

Answer below.








Answer is C. I'm trying to understand something. Voltage in solution? I thought a voltage occurs only when the two reactions are separated and are connected via metal that enables the redox reaction. Then each cell will have a potential and a voltage can form.

THIS question is suggesting that it all occurs in the same solution. Can a voltage develop?

I think you might be getting confused because you are trying to equate titration with electrochemistry (galvanic/electrolytic cells). In my mind they are only peripherally related.

In a titration you are adding an acid to a base, base to an acid, oxidizing agent to reducing agent, or whatever else. So you have one in the buret, and the other in a flask. Regardless of which one is where initially, they both end up in the flask together and react in the flask only. The reaction is completely contained within the flask (except for explosions, vapor, etc etc). The voltage is always going to increase because you are moving around electrons in a redox reaction.

In your question, you are alluding to galvanic cells, which as you say have two separate solutions. These solutions are connected by an emf circuit and a salt bridge. The emf is to drive the redox reaction (cathode/anode) and the salt bridge is to distribute the charge that, without the salt bridge, would build up on the cathode solution (since reduction occurs there) and your reaction would not be able to proceed. You only need to separate the solutions to keep the reaction going, not to make it happen.

 

[chiddler]

So voltage must refer to how much reaction happens. There isn't a voltage in a circuit like sense, but there is a voltage because there is a potential difference between the redox pair.

Then my mistake was what voltage meant.

thanks.

 

[rjosh33]

In a redox titration, if the voltage in solution rises:
A. Reducing agent must be the titrant
B. Oxidizing agent must be titrant.
C. Titrant can be either.

Answer below.








Answer is C. I'm trying to understand something. Voltage in solution? I thought a voltage occurs only when the two reactions are separated and are connected via metal that enables the redox reaction. Then each cell will have a potential and a voltage can form.

THIS question is suggesting that it all occurs in the same solution. Can a voltage develop?

Yes, it can all be in the same solution in just one beaker. To establish a voltage, one can use a standard electrode on one end (made of silver, for example), and use what's called a double-junction electrode on the other end. The double junction electrode basically has a couple of different compartments to isolate it from the solution, allowing the difference in voltage to develop.

It's actually much easier to use something like this as a reference electrode, rather than the usual Standard Hydrogen Electrode, in which hydrogen gas has to be pumped in and a clean Platinum catalytic surface prepared.

 

[HollowSuperet36]

A good example is the ammonium production passage in AAMC 11 PS 1

 

[SaintJude]

Can anyone explain how a redox titration works and is related to voltage changes. Tried to look it up online, but found no good sources.

So how is the equivalence point found? Is indicated by rapid voltage changes like that of pH based titration?

How do you find when [reduced element] = [original element]?

 

[HollowSuperet36]

I think you're over thinking it. Just view it as you have a solution of two species capable of a redox reaction with it self. Can you add one or the other to cause the reaction to happen? Of course you can.

Honestly I haven't heard of it before your question but it makes sense. I think that's all you need from it. If there's more I'd like to know it as well. But I don't think we do.

 

[MedPR]

Can anyone explain how a redox titration works and is related to voltage changes. Tried to look it up online, but found no good sources.

So how is the equivalence point found? Is indicated by rapid voltage changes like that of pH based titration?

How do you find when [reduced element] = [original element]?

Think of it in terms of a reaction happening. In the beaker you start with something that is either very oxidized, or very reduced, or neutral. Then you add in the titrant and a redox happens. Remember how the half reactions have Ecell potentials? Those are voltages.