Cell potential

[Ann Zhang_1M]

when we calculate the standard cell potential of a redox reaction, how do we know if we should add two values or subtract. I am so confused.

[Laura Rabichow 1J]

Figure out which one is the anode and which is the cathode, then do Ecathode - Eanode to get the standard cell potential.

[Megan Yabumoto 3K]

The given values for standard cell potential of the half reactions are given as reductions. In order to calculate the cell potential of the oxidation reaction, you take the opposite sign of the value given for the reduction. If you reverse the sign of the oxidation reaction, then you add the values of the reduction and oxidation.

You can also keep both values of the standard cell potentials as the reduction potentials, and in that case you would subtract the value for the oxidation (without changing the sign) from the value for the reduction.

I hope this makes sense...

[Carolyn Huh 1K]

For a standard cell potential of a redox reaction, utilize the equation E(Cathode)-E(Anode) to calculate the standard cell potential.

[Myra_Zhan_2N]

When you utilize E(cathode)-E(anode), take note that both are given as a reduction reaction value so be sure to check the negatives and positives.