Quick electrochemistry question

[hs2013]

When calculating the Ecell values and manipulating the oxidation and reduction reactions, why don't the Ecell values from the standardized table getting flipped? Why is it the same when the reaction is oxidation and reduction?

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[ipmed]

The Ecell Value from a table are the reduction potentials, and they flip along with the reaction when speaking about oxidation of a species respective reduced compunt. for example
H + 2e- = H2 has a E=1
H2 = H + 2e- has a E=-1

 

[hs2013]

The Ecell Value from a table are the reduction potentials, and they flip along with the reaction when speaking about oxidation of a species respective reduced compunt. for example
H + 2e- = H2 has a E=1
H2 = H + 2e- has a E=-1

EDIT:**** nvm, I see that you say they flip, but in my chemistry class when calculating stuff, such as Ecell values of two half reactions, when one is oxidation, but in the reduction potential table it shows that same reaction in the reduction state(or flipped), you still use the same value, you don't flip it...

 

[hs2013]

I'm just so confused now, how do you know when to flip and when to keep it as is?

I use the equation... Ecell=E(substance reduced)-E(substance oxidized)
So in an example like...
Values from table
Co^2+ + 2e- >>> Co E= -0.28
2H^+ + 2e- >>> H2 E=0

Co + H^+ >>> Co^2+ + H2

isn't your oxidation reaction the Cobalt one, and the reduction reaction is the Hydrogen and they would be written in half reactions as..
oxidation: Co >> Co^2+ + 2e-
reduction: 2H^+ + 2E- >> H2

So when you use the equation I had above, for the substance reduced, it E would be 0, but for the substance oxidized, in the table the reaction is flipped from the half reaction in the equation, but my book says still do (0) - (-0.28) so I don't get why my book doesn't have my flip it?

 

[ipmed]

Keep in mind its Ecell=Ereduction - Ereduction, but if you already reverse the sign of the reduction potential for the species being oxidized, then its Ecell=Ereduction + Eoxidation

 

[hs2013]

Keep in mind its Ecell=Ereduction - Ereduction, but if you already reverse the sign of the reduction potential for the species being oxidized, then its Ecell=Ereduction + Eoxidation

Yea I understand it now, what tripped me up was I didn't know about the addition equation. I wish it was just taught in the addition method and flipping, because that makes more sense, or professors should take more time to explain both. But thankfully now it's an easy concept