Problem: Consider a galvanic cell built on the following half-reactions with their standard reduction potentials shown. What is ΔG° at 25 °C for the reaction involved?Cr2O72- + 14H+ + 6e- <=> 2Cr3+ + 7H2O    E° = 1.42 VH2O2 + 2H+ + 2e- <=> 2 H2O    E° = 1.90 V

We are asked to find the ΔG° at 25 °C for the reaction. We will use the Nernst Equation to calculate the cell potential. The Nernst Equation relates the concentrations of compounds and cell potential.

$\boxed{\mathbf{\Delta G}\mathbf{°}\mathbf{ }\mathbf{=}\mathbf{ }\mathbf{-}\mathbf{nFE}\mathbf{°}}$

E°_cell = standard cell potential
n = number of e^- transferred

We have to determine the E°_cell first and as well as the anode (oxidation) and cathode (reduction) in the concentration cell and the number of electrons transferred (n).