Question

Consider the following redox reaction:Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)Calculate the standard free energy change (ΔG°) for the reaction at 298K, given that the standard reduction potentials for Cu2+(aq)/Cu(s) and Ag+(aq)/Ag(s) are +0.34V and +0.80V, respectively.

Answer 1

To calculate the standard free energy change  G  for the redox reaction, we first need to determine the overall cell potential  E  for the reaction. The cell potential can be found using the standard reduction potentials given:E cell  = E cathode  - E anode In this reaction, silver ions  Ag+  are reduced to silver metal  Ag , so the silver half-reaction is the cathode. Copper metal  Cu  is oxidized to copper ions  Cu2+ , so the copper half-reaction is the anode.E cell  = E Ag+/Ag  - E Cu2+/Cu E cell  =  +0.80 V  -  +0.34 V E cell  = +0.46 VNow that we have the cell potential, we can calculate the standard free energy change  G  using the following equation:G = -nFE cell where n is the number of moles of electrons transferred in the reaction, F is Faraday's constant  96,485 C/mol , and E cell  is the cell potential.In this reaction, 2 moles of electrons are transferred  from Cu to 2Ag+ :G = - 2 mol  96,485 C/mol  +0.46 V G = -88,766 J/molSince the standard free energy change is typically expressed in kJ/mol, we can convert the units:G = -88.77 kJ/molSo, the standard free energy change  G  for the given redox reaction at 298 K is -88.77 kJ/mol.