Consider the galvanic cell consisting of the following two redox couples: Ag^- (
ID: 975385 • Letter: C
Question
Consider the galvanic cell consisting of the following two redox couples: Ag^- (0.010 M) + e^- rightarrow Ag(s) Delta degree = +0.80 V Cr^3+ (0.010 M) + 3e^- rightarrow Cr(s) E degree -0.74 V Write the equation for the half-reaction occurring at the cathode. Write the equation for the half-reaction occurring at the anode. Write the equation for the cell reaction. What is the standard cell potential, E degree for the cell? Realizing the nonstandard concentrations, what is the actual cell potential, E for the cell? The extent of corrosion in the steel reinforcing rods (rebar) of concrete is measured by the galvanic cell shown in the diagram of the instrument. The half-cell of the probe is usually a AgCl/Ag redox couple: AgCl + e^- rightarrow Cl^- (1.0 M) E degree = +0.23 V Corrosion is said to be severe if the cell potential is measured at greater than 0.41 V. Under these conditions, what is the iron (II) concentration on the rebar? Fe^2+ + 2e^- rightarrow Fe E degree = -0.44 VExplanation / Answer
a) Reaction occuring at Cathode
Ag(+)(aq) + e- ---------------------- Ag(s), Ecell = 0.80V
b) Reaction occuring at Anode
Cr(s) -------------------- Cr(3+) + 3e-, Ecell = 0.74V
c) Equation for cell reaction
3Ag(+)(aq) + Cr(s) ---------------- Cr(3+) + 3Ag(s)
d) Eocell = Ecell(oxidation) + Ecell(reduction)
=> 0.80+ 0.74
=> 1.54V
e) Equlibrium constant K = [Cr(3+)]/[Ag+]^3 = 10^4
Ecell = Eocell - 0.0596/3 * log(10^4)
=> 1.54V - 0.0596/3 * 4
=> 1.4605V