Problems 8
289
solution to which a small amount of LiOH is added. The chemical reaction
that occurs on discharge is
Fe + 2Ni(OH) 3 ?± Fe(OH) 2 + 2Ni(OH) 2
Write the half-cell reactions for the electrodes. Which pole must be the negative pole?
7. Equilibrium constants for the following reactions may be found in the tables
cited. Calculate AG° for each of the reactions at 25.0°C.
(a) HC 2 H 3 O 2 <=t U
+ + C 2 H 3 O 2 -
(Table 23-1)
(b) NH 3 + H 2 O <=± NH 4
+ + OH(Table 23-1)
(c) Ag 2 CrO 4 5=s 2Ag
+ + CrOj*
(Table 24-1)
(d) Ag(NH 3 ) 2
+ f± Ag
+ + 2NH 3
(Table 25-1)
(e) N 2 0 4<9) ?± 2N0 2(91
(Table 16-1)
8. Calculate AG° and K e at 25.0°C for each of the reactions listed. Tell which
ones are spontaneous.
(a) H 2 S (9) + 30 2(9) -* 2H 2 O m + 2SO 2(9)
(b) 2CH 3 OH< ;) + 30 2(9) -^ 2C0 2(9) + 4H 2 O ((1
(c) 2N0 2(fl) -> 2NO (fl) + 0 2(9)
(d) I 2(8) + 2HBr <9) -H> 2HI (9) + Br 2(()
9. Calculate AS
0 for each of the reactions in Problem 8.
10. Calculate A//° for each of the reactions in Problem 8, but do not use data
given in Table 14-1.
11. Calculate values of K e at 25.0°C for the following equilibria, using data from
Table 17-1 exclusively.
(a) AgBr, s) ?± Ag (
+
aQ) + Brf a9)
(b) 2H 2(9) + 0 2(9) <=t 2H 2 O a)
(c) 2H 2 0 2(() ?± 2H 2 0 U) + 0 2(9)
12. Use the value of A//° obtained in Problem 28(c), p. 226, for the reaction Ba,
2
,^,
+ SOI'Jn,,) ?i BaSO 4( ,,, along with information given in Table 24-1; to calculate the value of AS
0 for this reaction.
PROBLEMS B
13. Make a simple sketch to show how you would arrange the materials used in
constructing batteries that utilize the following chemical reactions. For each
battery, also show the polarity, the directions of flow of electrons and ions,
and the half-reaction that occurs in each cell.
(a) 2La + 3Cu
2+ *± 2La
3+ + 3Cu
(b) Zn + Hg+ <=s Zn
2+ + 2Hg
(c) Fe + C1 2 ?± Fe
2+ + 2C1~
(d) Sn + Sn
4+ *± 2Sn
2+
(e) 2Hg + C1 2 *^ Hg 2 Cl 2