24.2.4—A standard cell potential by combining two

For a galvanic cell, E°cell = E°cathode − E°anode, using both values as reduction potentials. The cathode is where reduction occurs and the anode where oxidation occurs.

Balance half-equations separately, but never multiply E° values by stoichiometric coefficients. A positive E°cell indicates a thermodynamically favourable standard-cell direction.

Cu²⁺/Cu = +0.34 V and Zn²⁺/Zn = −0.76 V give E°cell = +1.10 V for Zn oxidation and Cu²⁺ reduction.

Do not add two reduction potentials or reverse a value without also reversing the half-equation direction.