TBR Bio 2 Typo?

[MedPR]

TBR Bio Chapter 7 Passage 3 question 17.

It is based on the following reaction.

H2O2 ---> 2H+ + O2 + 2e-

The above reaction occurs at a platinum electrode. The question is:


The function of the platinum electrode in this probe is to act as:

A. a cathode
B. an anode
C. oxidizing agent
D. oxidase

Explanation: Oxidation occurs at the anode. The H2O2 is oxidized. The platinum acts as a reducing agent. Platinum acts as an anode. Choices A and C are incorrect. An oxidase is an enzyme. It plays a role in the first reaction. Choice D is incorrect. Choice B is correct.

If H2O2 is oxidized at the Pt electrode, doesn't that mean Pt is an oxidizing agent? Shouldn't the answer be C? Further, if it is an oxidizing agent, doesn't that also mean it acts as an anode? So B or C is correct? So overall this problem is stupid and TBR should send me a check since I've found like 8 thousand typos so far?

Edit: I just realized this is kind of an aggressive post. I really hope I'm right or else:

1. I don't understand redox nearly as well as I think I do
2. I'll look really stupid for calling out TBR, when they are in fact correct and just tricked me.

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[chiddler]

i think because it's an electrode, B is a better answer. C is true, but B is a better answer as B is its primary function.

does seem like a cheap shot, though. i might be wrong, but i also vaguely remember the passage giving some information to help with this question.

 

[MedPR]

i think because it's an electrode, B is a better answer. C is true, but B is a better answer as B is its primary function.

does seem like a cheap shot, though. i might be wrong, but i also vaguely remember the passage giving some information to help with this question.

The answer explanation says that Pt is a reducing agent.

 

[davcro]

Choice B and C are the same. I'd say anode is a better definition because the platinum is being used in a galvanic cell (i haven't read the passage, but I'm assuming this). Poor question IMO.

Don't get me started on typos in TBR. I understand your frustration. A typo wastes time and undermines confidence. I wish people had warned me about them before I started studying.

 

[davcro]

Just saw that the answer explanation said platinum is a reducing agent. Definitely a typo. It's oxidizing the h2o2

 

[chiddler]

sorry. when i think of answer i get excited and forget everything else.

The answer explanation says that Pt is a reducing agent.

i think you're right then. it must be an error. o2 is most oxidized possible thing ever. it is oxidized. the other thing is reduced. it is the oxidizing agent. your logic is spot on.

 

[MedPR]

Ok thanks guys. Is there any reason that "anode" is a better answer than "oxidizing agent"?

 

[SaintJude]

It may just be a better reason b/c the "anode" refers specifically to the situation of a battery or a electrolysis operation--which that passage is specifically dealing with (Don't have TBR, so not familiar with passage)

But AAMC would not have both choices as options anyway since they're both valid like others said.

 

[gettheleadout]

Yeah, even bothering to try and determine why B or C is "better" when they're both correct is a waste of time and effort. Blame TBR.

 

[MrNeuro]

Your mistaking this question/setup with a galvanic cell.

In this cell platinum is not reacting with H2O2, the platinum is just serving as a conductor of electrons. A reducing agent is something that get oxidized or loses electrons. In this setup the e- from the H2O2 are travelling from the Pt to some recording device that measures e-. So the anode is losing electrons which is consistent with it being oxidized and hence a reducing agent. I personally feel that calling it a reducing agent is going a bit too far but i can see how it is justifiable.

i think the Pt may also be acting as a catalyst for H2O2 oxidation....

this question made my head hurt for a while

 

[MedPR]

Your mistaking this question/setup with a galvanic cell.

In this cell platinum is not reacting with H2O2, the platinum is just serving as a conductor of electrons. A reducing agent is something that get oxidized or loses electrons. In this setup the e- from the H2O2 are travelling from the Pt to some recording device that measures e-. So the anode is losing electrons which is consistent with it being oxidized and hence a reducing agent. I personally feel that calling it a reducing agent is going a bit too far but i can see how it is justifiable.

i think the Pt may also be acting as a catalyst for H2O2 oxidation....

this question made my head hurt for a while

How can Pt AND H2O2 be reducing agents? H2O2 loses electrons (is the reducing agent) and those electrons must go somewhere. They go to the Pt so the Pt can relay them to the voltmeter or whatever they are using. So the Pt is reduced.

 

[MrNeuro]

How can Pt AND H2O2 be reducing agents? H2O2 loses electrons (is the reducing agent) and those electrons must go somewhere. They go to the Pt so the Pt can relay them to the voltmeter or whatever they are using. So the Pt is reduced.

the Pt is acting as a conductor. take it one step further those electrons travel to another electrode making that electrode the cathode and the platinum electrode the anode because thats the location of oxidation.


Wiki anode and you'll see this

An anode is an electrode through which electric current flows into a polarized electrical device. The direction of electric current is, by convention, opposite to the direction of electron flow. In other words, the electrons flow from the anode into, for example, an electrical circuit. Mnemonic: ACID (Anode Current Into Device).

that help?

 

[MedPR]

the Pt is acting as a conductor. take it one step further those electrons travel to another electrode making that electrode the cathode and the platinum electrode the anode because thats the location of oxidation.


Wiki anode and you'll see this


that help?

Yes, oxidation occurs at the anode because the anode is an oxidizing agent and is therefore reduced.

 

[MrNeuro]

Yes, oxidation occurs at the anode because the anode is an oxidizing agent and is therefore reduced.

If the platinum were getting reduced you'd expect the following Pt ==> Pt- right?

the platinum i believe remains the same and just acts as a catalyst to oxidize H2O2...thats why i think calling it a reducing agent is going a little too far but the way TBR possibly justifies this is by saying that the electrons leave the Pt electrode and you get a net Positive charge in the region where the pt electrode is located making it the anode b/c electrons are flowing OUT of the area where the Pt electrode is located.

better?

 

[MedPR]

If the platinum were getting reduced you'd expect the following Pt ==> Pt- right?

the platinum i believe remains the same and just acts as a catalyst to oxidize H2O2...thats why i think calling it a reducing agent is going a little too far but the way TBR possibly justifies this is by saying that the electrons leave the Pt electrode and you get a net Positive charge in the region where the pt electrode is located making it the anode b/c electrons are flowing OUT of the area where the Pt electrode is located.

better?

I don't think the Pt has to change to Pt- just because it is accepting electrons.. As you said, it is acting as a conductor to create current so the rest of the setup can read the glucose concentration (or whatever this was for, I don't even remember). It accepts the electrons from the H2O2 reaction and passes them on. I agree that it acts as a catalyst, but like in a real galvanic cell, it will eventually wear down.

 

[MrNeuro]

I don't think the Pt has to change to Pt- just because it is accepting electrons.. As you said, it is acting as a conductor to create current so the rest of the setup can read the glucose concentration (or whatever this was for, I don't even remember). It accepts the electrons from the H2O2 reaction and passes them on. I agree that it acts as a catalyst, but like in a real galvanic cell, it will eventually wear down.

im confused are we agreeing or disagreeing??? LOL

 

[MedPR]

im confused are we agreeing or disagreeing??? LOL

I think we're agreeing!

 

[MrNeuro]

I think we're agreeing!

sweet lol