Hemichordate

Peds
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May 5, 2008
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If you have two equations and one equation is more negative than the other (i.e. -0.75 V vs -0.30 V), is the compound in the more negative half-reaction more easily oxidized and the more positive half-reaction more more easily reduced?

Does this also indicate the more negative half-reaction has a greater probability of being oxidized?
 

minutemen11

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Jun 7, 2009
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it depends on whether the half reactions are reduction potentials or oxidizing potentials. MCAT will mostly give only reduction potentials, so, that with the higher (less negative) potential will be reduced and that will the lower (more negative) potential will be oxidized.

So if you have a substance that has half reactions of -1V and -2V (assuming these are reductions potentials). The -1V half reaction will be reduced and the -2V will be oxidized IN A GALVANIC cell since you do cathode-anode (-1+2)=1V.

However, if you wanted to make an electrolytic cell out of these half reactions the total potential of the half-reations must add up to a negative voltage; therefore (-2+1)=-1V. This means that the half-reaction that would normally be reduced in a galvanic cell is actually oxidized in a electrolytic cell. The negative voltage is needed because thats what the battery will try to overcome and power the cell

At least I think thats right?
 

G1SG2

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May 2, 2008
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If you have two equations and one equation is more negative than the other (i.e. -0.75 V vs -0.30 V), is the compound in the more negative half-reaction more easily oxidized and the more positive half-reaction more more easily reduced?

Does this also indicate the more negative half-reaction has a greater probability of being oxidized?
Yes, the compound with the more positive reduction potential will be reduced. So between -0.75 and -0.30, the one with -0.30 will be reduced. Flipping the signs will give you the oxidation potentials. 0.75 is greater than 0.30, and so that will be oxidized.
 
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