Fe2+(aq)|Fe(s) -0.44 V and Zn2+(aq)|Zn(s) -0.76 V and Cr3+(aq)|Cr(s) ‑0.74 V and Cu2+(aq)/Cu(s) +0.34 V. Calculate the standard free energy change:
Fe2+(aq) + Cr(s) --- Fe(s) + Cr3+(aq)?

Question

Fe2+(aq)|Fe(s) -0.44 V and Zn2+(aq)|Zn(s)  -0.76 V and  Cr3+(aq)|Cr(s)  ‑0.74 V  and Cu2+(aq)/Cu(s) +0.34 V. Calculate the standard free energy change:
Fe2+(aq)  +  Cr(s)  --->   Fe(s) + Cr3+(aq)?

Ellie Andrews · Accepted Answer

I think you are right and here's why:

#sf(Cr^(3+)+3erightleftharpoonsCr" "E^@=-0.74" "V)# #sf(Fe^(2+)+2erightleftharpoonsFe" "E^@=-0.44" "V)# In other words, the first 1/2 cell will be driven from left to right, and the second 1/2 cell from right to left. The response of the cell will be: #sf(3Fe^(2+)+2Crrarr3Fe+2Cr^(3+))# To find #sf(E_(cell)^@)# subtract the least +ve value from the most +ve: #sf(E_(cell)^@=-0.44-(-0.77)=+0.3color(white)(x)V)# The change in free energy is provided by: #sf(DeltaG^@=-nFE_(cell)^@)# where n, in this case equals 6, is the number of moles of electrons transferred. #:.##sf(DeltaG^@=-6xx9.65xx10^(4)xx0.3=-173.7color(white)(x)kJ)# Since free energy change is a large quantity, reactant and product concentrations affect it. This value refers to the equation as I have written it; the equation in the question is not balanced. Is the equation to which +683.1 kJ is given in the answer key specified? The + sign means the reaction is non - spontaneous. This is not the case indicated by the -ve sign of #sf(DeltaG^@)#.

Mateo Aguilar · Answer

undefined ΔG° = ΔE° - TΔS°
ΔE° = E°(cathode) - E°(anode)
ΔG° = -nFΔE°
n = number of moles of electrons transferred
F = Faraday's constant (96,485 C/mol)

Calculate E°(cathode) - E°(anode) for the given reaction:
E°(cathode) = E°(Fe2+/Fe) + E°(Cr3+/Cr)
E°(anode) = E°(Zn2+/Zn) + E°(Cu2+/Cu)

Calculate ΔE° and then use it to find ΔG°.

Xavier Avery · Answer

undefined The standard free energy change ($\Delta G^\circ$) for the reaction is $+12.5$ kJ/mol.

Fe2+(aq)|Fe(s) -0.44 V and Zn2+(aq)|Zn(s) -0.76 V and Cr3+(aq)|Cr(s) ‑0.74 V and Cu2+(aq)/Cu(s) +0.34 V. Calculate the standard free energy change: Fe2+(aq) + Cr(s) ---&gt; Fe(s) + Cr3+(aq)?

Fe2+(aq)|Fe(s) -0.44 V and Zn2+(aq)|Zn(s) -0.76 V and Cr3+(aq)|Cr(s) ‑0.74 V and Cu2+(aq)/Cu(s) +0.34 V. Calculate the standard free energy change: Fe2+(aq) + Cr(s) ---> Fe(s) + Cr3+(aq)?