Question

Calculate the standard free energy change (ΔG°) for the following reaction at 25°C: 2Fe2+(aq) + Cu2+(aq) -> 2Fe3+(aq) + Cu+(aq) (Standard reduction potentials: Fe3+(aq) + e- -> Fe2+(aq)    E° = 0.77 V Cu2+(aq) + e- -> Cu+(aq)     E° = 0.16 V)

Answer 1

To calculate the standard free energy change  G  for the given reaction, we first need to determine the overall cell potential  E  for the reaction. We can do this by subtracting the reduction potential of the half-reaction that will be reversed  oxidation  from the reduction potential of the half-reaction that will remain as reduction.In this case, the Fe2+ is being oxidized to Fe3+, so we will reverse the first half-reaction:Fe2+ aq  -> Fe3+ aq  + e-    E = -0.77 VThe second half-reaction remains the same:Cu2+ aq  + e- -> Cu+ aq      E = 0.16 VNow, we can add the two half-reactions together:2 Fe2+ aq  -> Fe3+ aq  + e-     2E = -1.54 VCu2+ aq  + e- -> Cu+ aq         E = 0.16 V----------------------------------------------2Fe2+ aq  + Cu2+ aq  -> 2Fe3+ aq  + Cu+ aq     E = -1.54 + 0.16 = -1.38 VNow that we have the overall cell potential  E , we can calculate the standard free energy change  G  using the following equation:G = -nFEwhere n is the number of moles of electrons transferred  in this case, 2 , F is Faraday's constant  96,485 C/mol , and E is the overall cell potential.G = -2 * 96,485 *  -1.38 G = 266,298 J/molSo, the standard free energy change  G  for the given reaction at 25C is 266,298 J/mol.