Chemical Thermodynamics of Tin - Volume 12 - OECD Nuclear ...

A Discussion of selected references
367
HClO4
Table A-42: Concentration basis at 25 °C [1979VAS/GLA].
c /M c
4
/M c
2
/M I/M [H + ]/M [Sn 4+ ]/M [Sn 2+ ]/M E/V
SnCl
SnCl
2.000 0.010130 0.023750 2.116 2.011 0.002689 0.012030 0.16340
2.000 0.016330 0.013310 2.140 2.017 0.004352 0.006124 0.17760
2.000 0.019350 0.010600 2.154 2.021 0.005161 0.004784 0.18309
2.000 0.015000 0.018680 2.141 2.016 0.003987 0.008313 0.17190
3.000 0.009208 0.022760 3.111 3.008 0.003423 0.010540 0.15194
3.000 0.005000 0.021840 3.138 3.012 0.005584 0.011470 0.15720
3.000 0.007489 0.026650 3.104 3.006 0.002783 0.013030 0.14650
3.000 0.007598 0.002879 3.110 3.006 0.002824 0.012790 0.14710
3.000 0.017400 0.006085 3.142 3.014 0.006481 0.002603 0.17800
4.000 0.025930 0.004071 4.192 4.019 0.011120 0.001562 0.17880
4.052 0.026510 0.003595 4.221 4.071 0.011470 0.001354 0.17990
4.000 0.026500 0.003500 4.194 4.019 0.011360 0.001347 0.17960
4.000 0.003491 0.023620 4.086 4.030 0.001491 0.011370 0.12771
4.000 0.014720 0.007791 4.117 4.011 0.006289 0.004272 0.15810
The standard potential
ο
E (Sn 4+ /Sn 2+ ) of Eq. (A.74) is defined by
⎧ 4 4
o 4 2
m + p
Sn H
γ +
+ + ⎪ ⎡ ⋅ ⎤ ⎡ ⎤⎫
2
Sn ⎪
E (Sn /Sn ) = E− ( k/2) ⎨log10 ⎢ log
2⎥+
10 ⎢ 2⎥⎬
. (A.74)
m 2+ m + γ 2+ γ +
⎩⎪
⎣ ⋅
⋅
Sn H ⎦ ⎣ Sn H ⎦⎭⎪
It is assumed that H 2 is in its standard state, thus log10 p H = 0.
2
⎧
4
o
⎪ ⎡ m + ⎤⎫
Sn ⎪
Em ' = E−( k/2) ⎨log10 ⎢
2 ⎥⎬
⎪ m 2+ m +
⎩ ⎣ ⋅
Sn H ⎦⎪⎭
(A.75)
The SIT approach for HClO 4 as preponderant electrolyte leads to Eqs. (A.76)
and (A.77)
log
⎡ γ ⎤
⎥ =
⎣ ⎥⎦
4+
Sn
10 ⎢
2
⎢γ
2+ ⋅γ
+
Sn H
4+ − 2+ − + −
{ − 10 D+ ⎡ε(Sn ,ClO
4) ε(Sn ,ClO
4) 2 ε(H ,ClO
4)
⎤ m −
⎣
− − ⎦⋅
ClO }
o o 4+ 2+
m
−
ClO4
4
(A.76)
E ' + ( k/2) ⋅ 10 D = E (Sn /Sn ) +Δ ε·
m
(A.77)
o 4+
2+
The standard potential E (Sn / Sn ) = (0.2740 ± 0.0010) V arrived at by
evaluating these data using the SIT approach, see Figure A-41, agrees reasonably with
o 4+ 2
that recalculated by Hummel et al. E (Sn /Sn + ) = (0.289 ± 0.006) V
[2002HUM/BER], who were the first to recognise the sign error of [1979VAS/GLA].
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012