Question

Taking the activity coefficient effect into consideration,
calculate the concentration of Fe^{3+} in a solution that
is saturated with Fe_{4}[Fe(CN_{6}]_{3}
(Iron(III) ferrocyanide). The overall ionic strength of the
solution is .01 M.

Iron(III) ferrocyanide Ksp = 3.3*10^{-41}.

The answer starts with 5.90... please show ALL steps

Answer #1

Fe_{4}[Fe(CN_{6}]_{3} <--->
4Fe^{3+} + 3[Fe(CN_{6}]^{4+}

K_{sp} =(
a_{Fe3+})^{4}(a_{[Fe(CN6]4+})^{3} =
a_{+}^{4}a_{-}^{3} =
(c_{+}γ_{+} )^{4} (c_{-}
γ_{-} )^{3}

= (c_{+})^{4} (c_{-})^{3}
(γ_{+})^{4}(γ_{-})^{3}

= (c_{+})^{4} (c_{-})^{3}
(γ_{+
-})^{7 }
; γ_{+ -} = mean ionic activity coefficient

If solubility of Fe_{4}[Fe(CN_{6}]_{3}
is S, then we can write, c_{+} = 4S; c_{-} = 3S

K_{sp} = (4S)^{4} (3S)^{3} (γ_{+
-})^{7}

= 6912* S^{7}* (γ_{+ -} )^{7}

According to Debye-Huckel limiting law; log (γ_{+
-}) = - 0.509 Z^{+}Z^{-} √I

or, log (γ_{+ -}) = - 0.509 * 3 * 4 √0.01 = 0.244

Activity solubility product, K_{sp} = 9.18 *
10^{-41}

= 6912* S^{7}* (0.244 )^{7}

or, S = 1.907*10^{-6}

[Fe^{3+}] = 4S = 7.6 * 10^{-6} M

A)Calculate The activity coefficient of Pb2+ at an ionic strength
of 0.40. What does this value mean? B) determine the solubility of
PbCO3 in the solution of ionic strength of 0.40. (Note the activity
coefficient of the carbonate ion is the same as that for the Pb2+,
why is that?) compare this solubility to the solubility of PbCO3 in
pure water. C) write the mass balance and charge balance equations
for a solution that is 0.20 M in NaF and...

Using activities, find the concentration of Ba+2 in a
0.100M (CH3)4N+
IO3- solution saturated with
Ba(IO3)2. Assume
Ba(IO3)2 makes a negligible contribution to
the ionic strength and the Ksp value is 1.5 X
10-9
PLEASE SHOW ALL STEPS!

Question 8. Suppose ZnS(s) is saturated with 0.04 M K2S (K2S
completely dissolves and ZnS has limited solubility) (Ksp for ZnS
is 2x10-25)
(a) (2 pts) What is the ionic strength of the solution? Show
calculations
(b) (4 pts) What are the activity coefficients of each
specie?(Please apply Debye Hückel equation given in lecture notes
considering the size of the ion if necessary)
(c) (4 pts) What is pZn by taking activity coefficients into
consideration? Please show calculations

Including activity coefficients, calculate the concentration of
Pb2+ in a 0.100 M aqueous solution of NaIO3
saturated with Pb(IO3)2. (Hint: look up the
Ksp value for Pb(IO3)2.

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