Exercises 897075.Identify all of the terms in the Nernst equation. What
part of the Nernst equation represents the correction fac-
tor for nonstandard electrochemical conditions?
076.By putting the appropriate values into the Nernst equa-
tion, show that it predicts that the voltage of a standard
half-cell is equal to E^0. Use the Zn^2 /Zn reduction half-
cell as an illustration.
*077.Calculate the potential associated with the following half-
reaction when the concentration of the cobalt(II) ion is
1.0 10 ^3 M.
Co(s)88nCo^2 2 e078.Calculate the reduction potential for hydrogen ion in a
system having a perchloric acid concentration of 2.00
10 ^4 Mand a hydrogen pressure of 2.50 atm. (Recall that
HClO 4 is a strong acid in aqueous solution.)
079.The standard reduction potentials for the H/H 2 (g) and
O 2 (g), H/H 2 O() couples are 0.0000 V and 1.229 V,
respectively.
(a) Write the half-reactions and the overall reaction, and
calculate E^0 for the reaction
2H 2 (g)O 2 (g)88n2H 2 O()(b) Calculate Efor the cell when the pressure of H 2 is
3.00 atm and that of O 2 is 1.30 atm.
*080.Consider the cell represented by the notation
Zn(s)ZnCl 2 (aq)Cl 2 (g, 1 atm); Cl(aq)CCalculate (a) E^0 and (b) Efor the cell when the concen-
tration of the ZnCl 2 is 0.25 mol/L.
081.What is the concentration of Agin a half-cell if the
reduction potential of the Ag/Ag couple is observed to
be 0.45 V?
082.What must be the pressure of fluorine gas to produce a
reduction potential of 2.75 V in a solution that contains
0.38 MF?
083.Calculate the cell potential of each of the following elec-
trochemical cells at 25°C.
(a) Sn(s)Sn^2 (4.5 10 ^3 M)Ag(0.110 M)Ag(s)
(b) Zn(s)Zn^2 (0.500 M)
Fe^3 (7.2 10 ^6 M), Fe^2 (0.15 M)Pt
(c) PtH 2 (1 atm)HCl(0.00880 M)Cl 2 (1 atm)Pt
084.Calculate the cell potential of each of the following elec-
trochemical cells at 25°C.
(a) PtH 2 (10.0 atm), H(1.00 10 ^3 M)
Ag(0.00549 M)Ag(s)
(b) PtH 2 (1.00 atm), H(pH5.97)
H(pH3.47), H 2 (1.00 atm)Pt
(c) PtH 2 (0.0361 atm), H(0.0100 M)
H(0.0100 M), H 2 (5.98 10 ^4 atm)Pt
0 *85.Find the potential of the cell in which identical iron
electrodes are placed into solutions of FeSO 4 of concen-
tration 1.5 mol/L and 0.15 mol/L.
0 *86.We construct a cell in which identical copper electrodes
are placed in two solutions. Solution A contains 0.75 M
Cu^2 . Solution B contains Cu^2 at some concentration
known to be lower than that in solution A. The poten-
tial of the cell is observed to be 0.040 V. What is [Cu^2 ]
in solution B?
0 *87.We construct a standard copper–cadmium cell, close the
circuit, and allow the cell to operate. At some later time,
the cell voltage reaches zero, and the cell is “run down.”
(a) What will be the ratio of [Cd^2 ] to [Cu^2 ] at that
time? (b) What will be the concentrations?
0 *88.Repeat Exercise 87 for a standard zinc–nickel cell.
0 *89.The cell potential for the cellZn(s)2H(_?_ M)88n
Zn^2 (3.0 M)H 2 (g) (5.0 atm)is observed to be 0.445 V. What is the pH in the H/H 2
half-cell?
*090.We wish to produce a 0.375-volt concentration cell using
two hydrogen electrodes, both with hydrogen at a pres-
sure of one atmosphere. One of the solutions has a pH
of 1.5. Calculate the required pH of the other solution.
*091.A concentration cell prepared using two hydrogen elec-
trodes, both with the partial pressure of hydrogen being
one atmosphere, produces 0.450 volts. The pH of one
hydrogen electrode is 1.65; what is the pH of the other?Relationships Among G^0 , E^0 cell, and K
*092.How are the signs and magnitudes of E^0 cell, G^0 , and K
related for a particular reaction? Why is the equilibrium
constant Krelated only to E^0 celland not to Ecell?
*093.In light of your answer to Exercise 92, how do you explain
the fact that G^0 for a redox reaction doesdepend on the
number of electrons transferred, according to the equa-
tion G^0 nFE^0 cell?
*094.Calculate E^0 cellfrom the tabulated standard reduction
potentials for each of the following reactions in aqueous
solution. Then calculate G^0 and Kat 25°C from E^0 cell.
Which reactions are spontaneous as written?
(a) MnO 4 5Fe^2 88n
Mn^2 5Fe^3 (acidic solution)
(b) 2Cu88nCu^2 Cu(s)
(c) 3Zn(s)2MnO 4 4H 2 O88n
2MnO 2 (s)3Zn(OH) 2 (s)2OH
*095.Calculate G^0 (overall) and G^0 per mole of metal for
each of the following reactions from E^0 values.
(a) Zinc dissolves in dilute hydrochloric acid to produce
a solution that contains Zn^2 , and hydrogen gas is
evolved.