The listed precipitates have the following Ksp values: These are, respectively,
ID: 920834 • Letter: T
Question
The listed precipitates have the following Ksp values:
These are, respectively, the hydroxides of improbablium (Im), unlikelium (Un), evanescentium (Ev), and mythium (My).
a. Assume all four metal ions, Im^1+, Un^2+, Ev^3+, and My^4+ are together in an acid solution, and each is 1mM. KOH is then slowly added with vigorous stirring. What is the order of precipitation of these four metal ions?
b. At what pH will each of the hydroxides just begin to precipitate - assuming equilibrium conditions, no metal hydrolysis, and negligible ionic strength effects?
ppt Ksp Im(OH) 6.0*10^-12 Un(OH)2 6.0*10^-12 Ev(OH)3 6.0*10^-12 My(OH)4 6.0*10^-12Explanation / Answer
a)My+4 ion willprecipitate first because the ionic product is more forMy(OH)4 than others
the order of precipitation is My+4>Ev+3>Un+2>Im+
b)at same pH they will precipitate i.e., 11
Im(OH)--------->Im+ + OH-
x x+10^-3 since1mM HCl is added
(x)*(x+10^-3)=6*10^-12
x=1.5*10^-9
[OH-]=1.5*10^-9+10^-3=0.001
pH=14-(-log(0.001))=11
if we solve for others we will get same pH values.
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