How do I write the full equation of a cell from two half cells? (basic, with matching electron counts and no water/acid)

Lets use an example:Fe3+(aq) + e- <==> Fe2+ (aq) E0 = +0.771 VLi+(aq) + e- <==> Li(s) E0 = -3.040 V
Step 1: Work out which half equation has the most positive standard electrode potential (E0) - this one will progress in the forward direction (as a reduction).In this case, the iron(II)/iron(III) half cell is more positive, so this will move in the forward directionStep 2: write the other half equation as an oxidation (flip the products and reactants over) and multiply its standard electrode potential by '-1'In our case, the Lithium cell will be progressing in the opposite direction, so we write it as so:Li(s) <==> Li+(aq) + e-And we give this equation: E0 = +3.040 VStep 3: add up the reactants and the products of each of these half cell equations, and cancel anything that appears on both sidesLi(s) + Fe3+ + e- <==> Li+ + Fe2+ + e- Here we can cancel the electrons, this is the full equation of the cellStep 4: work out the cell potential by doing Eox+EredEcell = 0.771 + 3.040 = 3.811 VThis tells us that there is a MASSIVE preference for the reaction to progress in this direction (as Lithium wants to lose its outer electron)

Answered by Fred P. Chemistry tutor

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