Question on Selective precipitation

  • Thread starter higherme
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  • #1
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can any one check if this is right?

question :
Explain if a solution contains both I− and Cl− at about 0.01 M, can we determine the amount of Cl− and I− independently by using gravimetric analysis?

yes
add [AG+] to precipitate out the I- first ( ksp is smaller)

0.01M * (0.01%/100%) = 1.0E-6 M I-
ksp = [Ag+][I-]
8.5E-17 = [Ag+](1.0E-6)
[Ag+] = 8.5E-11 M <------ add to precipitate AgI

increase [Ag+] to precipitate Cl- left
 

Answers and Replies

  • #2
Gokul43201
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Why are you multiplying the molarity by (0.01%/100%) ?
 
  • #3
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to lower the concentration:

i found using google:
"What do we mean by complete separation--> the concentration in solution of the analyte of interest must be less than or equal to 0.01% of its original value."
 
  • #4
Gokul43201
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Science Advisor
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Okay, so you want to remove 99.99% of I-. That's fine. You've calculated that it takes 8.5E-11M of Ag+ to precipitate most of the I-.

So far, so good. Now what do you need to calculate next?
 

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