use standard emf values to predict whether each of the following equations represent a reaction?

Question

that will occur in acid solution with all soluble substances present in 1M concentrations. Complere and balance the equation for each reaction that is predicted to occur;
a) H2O2 + Cu'2+ --> Cu + O2
b) H2O2 + Ag'+ --> Ag + O2
c) Ag'+ + Fe'2+ --> Ag + Fe'3+
d) Au + Cl2 --> Au'3+ + Cl'-

Answer 1

By "reaction" I assume you mean a reaction that will proceed under standard conditions.

For an electrochemcial process,

voltage x charge = free energy (true for electrical processes in general). Hence

E0 x -zF = DeltaG0

where zF is number of coulombs transferred, E is cell emf, DeltaG is free energy change and the minus sign is there because of our conventions,and the minus charge on the electron.

So to predict which reactions will occur, write down the standard reduction potential for the thing being reduced; write down the reduction potential WITH SIGN REVERSED for the thing being oxidized, and add them up. If the answer is positive, the reaction will go forward under standard conditions, which is what you are asked.

Balancing: lots of Q&A on Yahoo already on balancing redox equations. Do a search for them.