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

II.3 Standard and reference conditions 33
(atm)
(bar)
(atm)
⎛
rS r
S = δ R ln p ⎞
Δ − Δ ⎜ (bar) ⎟
⎝ p ⎠
= 0.1094 δ J·K –1·mol –1 (II.47)
where δ is the net increase in moles of gas in the process.
Similarly, the change in the Gibbs energy of a process between the two standard
state pressures is:
(atm)
(bar)
(atm)
⎛
rG r
G = δ RT ln p ⎞
Δ − Δ − ⎜ (bar) ⎟
⎝ p ⎠
= − 0.03263 δ kJ·mol –1 at 298.15 K. (II.48)
(bar)
(atm)
Eq. (II.48) applies also to ΔfG
− Δ
fG
, since the Gibbs energy of formation
describes the formation process of a compound or complex from the reference
states of the elements involved:
Δ G
− Δ G
(bar)
f f
(atm)
= − 0.03263 δ kJ·mol –1 at 298.15 K. (II.49).
The changes in the equilibrium constants and cell potentials with the change in
the standard state pressure follows from the expression for Gibbs energy changes,
Eq. (II.48),
(bar) (atm)
(bar) (atm) ΔrG
−ΔrG
log
10
K − log
10
K = −
RT ln 10
E
(atm)
⎛ p ⎞
ln ⎜ (bar) ⎟
(atm)
p
⎛ p ⎞
= δ
⎝ ⎠
= δlog10 ⎜ (bar) ⎟
ln10 ⎝ p ⎠
= 0.005717 δ (II.50)
(bar)
(bar) (atm) r r
− E
=
Δ G
−
−Δ G
nF
⎛ p
RT ln ⎜
p
= δ
⎝
nF
(atm)
(bar)
(atm)
⎞
⎟
⎠
0.0003382
= δ V at 298.15 K (II.51)
n
It should be noted that the standard potential of the hydrogen electrode is equal
to 0.00 V exactly, by definition.
H + e H (g) E = 0.00V
+ − 1 ο def
2 2
(II.52).
CHEMICAL THERMODYNAMICS OF TIN, ISBN 978-92-64-99206-1, © OECD 2012