CEM
834
PROBLEM
SET
1
FALL
2005
Due at the beginning of class on Friday, September 16, 2005
Note:
For this problem set, you may assume that all salts completely dissociate as given and
undergo no secondary equilibria.
We will address these assumptions later in this course.
Please
show your work, being careful of significant figures, units, etc.
1.
Calculate the ionic strength (I), individual molarities (C
+
, C

), individual activity
coefficients (
γ
+
,
γ

), and individual ionic activities (a
+
, a

) for each of the
electrochemically important solutions below.
Assume that all solutions are aqueous at 25
°C.
Use the DebyeHuckel limiting law (DHLL) or the extended DebyeHuckel equation
(EDHE), as appropriate, to calculate the activity coefficients.
a.
1.00 x 10
4
M KCl
KCl
→
K
+
+ Cl

b.
1.00 x 10
4
M Fe
2
(SO
4
)
3
Fe
2
(SO
4
)
3
→
2 Fe
3+
+ 3 SO
4
2
c.
1.00 x 10
4
M Ru(NH
3
)
6
Cl
3
Ru(NH
3
)
6
Cl
3
→
Ru(NH
3
)
6
3+
+ 3 Cl

d.
1.00 x 10
4
M K
4
Fe(CN)
6
K
4
Fe(CN)
6
→
4 K
+
+ Fe(CN)
6
4
How do your calculated molarities (C
+
and C

) compare with the values you determined
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 Fall '05
 MCGUFFIN
 Chemistry, Solubility, mean ionic activity

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