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# I need Help with clarifying Nernst equation watch

1. To start off thank you for any one who will be able to help me!

My problem is that in Nernst equation the formula goes as follows:

E=((RT)/(ZF))* ln(Ions outside)/(ions inside)

But my professor wrote it like this:

Phi(greek letter)= V2-V2= -(RT/ZF)* ln(ion out)/(ions in)

i understand the first equation but what i dont get his's, why did he write the negative sign when its not in the formula and what does V2 and V1 stand For, i tired asking him but with no luck , all he says "try and look it that up".

I will appreciate any help!

Thanks again.
2. (Original post by mohali26)
To start off thank you for any one who will be able to help me!

My problem is that in Nernst equation the formula goes as follows:

E=((RT)/(ZF))* ln(Ions outside)/(ions inside)

But my professor wrote it like this:

Phi(greek letter)= V2-V2= -(RT/ZF)* ln(ion out)/(ions in)

i understand the first equation but what i dont get his's, why did he write the negative sign when its not in the formula and what does V2 and V1 stand For, i tired asking him but with no luck , all he says "try and look it that up".

I will appreciate any help!

Thanks again.
In one, the potential difference is defined as outside-inside, in the other as inside-outside, ie multiply by -1. Also, bare in mind ln(x) = -ln(1/x)

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