Page 198 - Basic physical chemistry for the atmospheric sciences
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1 8 4 Basic physical chemistry
6. 1 4 . (a) Yes. (b) No. Hint: Determine whether or not any of
the oxidation numbers of any of the atoms is changed by
the reaction.
2
2Pb(s) + O z(aq) + 2 H 2 0(l) � 2Pb + ( aq) + 4 0H - (aq)
6 . 1 5 .
6. 1 6 . 4P4(s) + 2 0H - ( aq) + 1 2 H 2 0(l)� 1 2H2P02- (aq) + 4PH3(aq) .
1
Hint: See Exercises 6.2-6.4.
6. 1 7 . 02(g) i s the oxidant and C H 20 (s) the reductant.
6
6
1
2
2
)
6. 8 . Mn + ( aq , Fe + ( aq), Ag + (aq), 03(aq). Hint: See Table 6.2
1
and associated discussion in the text.
6. 1 9 . (a) Yes, it will. (b) A reductant. (c) Both. (d) No, it will not.
Hint: See Table . 2 and associated discussion in the text.
6
6 . 2 0. (a) It will . �en = 1 . 22 V . (b) It will not. � en = - 0.78 1 V .
Hint: See Exercise 6.6.
6.2 1 . aGO = 1 .05 x 105 J ; it is not a spontaneous reaction. Hint:
)
Use Eq . (6. 2 0 .
=
6.22. Kc 4 .57 x 1 0 - 19• The equilibrium state for the reaction lies
far to the left.
6 . 2 3 . £cel l = 0 . 769 V ; aG = - 1 . 48 x 105 J ; the forward reaction is
u
spontaneo s . Hint: Use the Nernst equation (6. 2 5) to obtain
t
a
£ at 250K from �e ll · Use n analogous expression o Eq.
cell
(6. 2 0) to obtain aG at 250K.
6 . 2 4. Maximum voltage = 1 2 . 2 46 V.
5
6.2 . [H + ( aq)] = 1 . 3 x 1 0 - 3 M . Hint: Use Eq. (6.26).
6.26. �ell = - 0.046 V. The reaction is not spontaneous u n der
standard condition .
s
Solution: HS03 (aq) + H 2 0(l) �
HS0 - ( aq) + 2H + (aq) + 2e -
4
From Eq. (6.20)
aV° = - n F�en
Therefore,
where n = 2 and F = 96,489 C and, from Eq . (2.34), a(JO
l . 2 V . Since aCo is nega
= - 227 kJ mol - 1 . Hence, �ell =
tive (and �en positive), the reaction is spontaneous under
standard conditions .
Fe 2 + (aq)
6.27. 782
FeH (aq)