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Chemistry- Selective Precipitation

by lananh
Tags: chemistry, precipitation, selective
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lananh
#1
Oct20-07, 07:57 PM
P: 4
1. The problem statement, all variables and given/known data

My molarity [I] is wrong which keeps me from ding the rest of this problem...any help would be greatly appreciated.

A researcher has a 450.0 mL solution that is 0.421 M in Hg2(NO3)2 and 0.0191 M in Pb(NO3)2. She plans to add solid potassium iodide to separate the mixture by selective precipitation.

Ksp PbI2 = 1.4e-8
Ksp Hg2I2 = 1.2e-28

What is the maximum concentration of iodide ions that may be in solution to achieve the best separation possible?

M [I-]= ?

How many grams of potassium iodide should she add to achieve this?

g of KI

What will the percentage of mercury(I) ions remaining in solution be?

% Hg2+2


2. Relevant equations
ksp= ...


3. The attempt at a solution
hg2i2 = hg2 + 2i
1.2e-28 = [.421][I]^2
[I]= 1.68e^-14, which is wrong and I have no idea what I am doing wrong
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Gokul43201
#2
Oct20-07, 11:38 PM
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P: 11,155
Quote Quote by lananh View Post
2. Relevant equations
ksp= ...
Ksp=??? Can you write down the expression for a general compound AmBn?


3. The attempt at a solution
hg2i2 = hg2 + 2i
1.2e-28 = [.421][I]^2
This calculation is not correct. First write down the correct expression for Ksp, then plug in numbers.
lananh
#3
Oct21-07, 11:15 AM
P: 4
thanks, but I already figured that out
I failed to realize it said MAXIMUM
so [i] would be ksp for pbi
[I] = 8.6e-2
but now I am having problems with b and c


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