AAMC10: Q24; oxid/reduction.

[pfaction]

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I am unsure if I can post this, so if I can't, I will delete it ASAP.

Can someone explain to me what the actual states of the molecules are?
2HCL+H2O2+MNO2 -> O2+MNCl2+2H2O
I understand:
HCL = H+1 CL-1
H2O2? I thought it would be +2/-2
MNO2: MN+4 O2-4
O2=0
MNCL2 = +2/-2
2H2O? +2/-2?

I got the question wrong because as usual I misread the ****ing question, it asked what the oxidizing and reducing agents were, not what was oxidized. I answered the opposite.

 

[MedPR]

Just wanted to say that you CAN post it, but I don't want to look because I am doing AAMC 10 in a few days 🙂

 

[pfaction]

Just wanted to say that you CAN post it, but I don't want to look because I am doing AAMC 10 in a few days 🙂

Don't read the topic, just read this, since I know you've taken other MCATS:
For the love of God, re-re-read the questions. I could have increased my score 2 points had I just read the ****ing question.

 

[Samchik]

In peroxides oxygen is -1.

In MnO2 (oxygen is -2 and Mn is -4).

 

[pfaction]

Thanks, the clears it up! So, H2O2 is +1/-1? For a total of +2/-2
So what about H2O? Is that +1, +1/-2?

 

[Samchik]

Yes, only in peroxides oxygen is -1, but in almost all other compounds it is -2.
In H2O (hydrogen is +1, oxygen -2) for a total of: H (+2) ; O (-2) ; since it is uncharged molecule the total oxidation state of the molecule must be zero.

 

[pfaction]

Thanks, man. The H2O2 still confuses me but I'll let it go as for what it is. So are my other oxidation states right, in terms of that? So, since MN4->MN2 it must be reduced, and acts as the oxidizing agent.

 

[Samchik]

Yes, you are correct regarding Mn; it is reduced (goes from +4 to +2).



Peroxides are just an exception to the rules, so don`t worry.

Look up the exceptions in your gen chem textbook or try google.

 

[pfaction]

I see, thanks. So in this case...which oxygen is "reduced"? I can't tell. H2O2 goes from -1 to 0 in O2, but goes to -2 in O2?

 

[Samchik]

Oxygen in peroxide is oxidized, since it goes from -1 to 0.

I found a similar thread, they discussed the same reaction:

http://forums.studentdoctor.net/showthread.php?t=445302

 

[mcloaf]

Don't read the topic, just read this, since I know you've taken other MCATS:
For the love of God, re-re-read the questions. I could have increased my score 2 points had I just read the ****ing question.

Heh, don't you love that feeling. 🙁