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Topic: Lead precipitation  (Read 6518 times)

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Ski Dude

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Lead precipitation
« on: July 15, 2005, 05:11:07 PM »
Need to precipitate lead from a concentrated calcium chloride solution w/o precipitating out the calcium.  Hydroxide addition (to form lead hydroxide) causes CaO to form and precipitate.  NaSH addition (to form a lead sulfide) is useful, but has some odor problems, and the possibility of forming H2S.

Any other suggestions?

Offline Borek

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Re:Lead precipitation
« Reply #1 on: July 15, 2005, 06:16:03 PM »
CrO42-
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arnyk

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Re:Lead precipitation
« Reply #2 on: July 15, 2005, 06:18:34 PM »
Check your solubility rules.  

Wait, so you're saying you have a concentrated CaCl2 solution WITH lead ions in it??  That sounds kind of wacky to me.

Ok let's say then it's a solution with Ca2+, Cl-, and Pb2+.

Add NaI to the solution, CaI2 is soluble and PbI2 will precipitate bright yellow.

Edit**:  But if those three initial ions were already in solution then the Pb2+ would have already reacted with the Cl- to form a precipitate.  

Hm, I guess I don't really understand the question then?  :-\
« Last Edit: July 15, 2005, 06:23:57 PM by arnyk »

Offline Borek

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Re:Lead precipitation
« Reply #3 on: July 15, 2005, 06:48:30 PM »
Edit**:  But if those three initial ions were already in solution then the Pb2+ would have already reacted with the Cl- to form a precipitate.  

Hm, I guess I don't really understand the question then?  :-\

Seems so :)

Have you ever heard about solubility product?
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arnyk

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Re:Lead precipitation
« Reply #4 on: July 15, 2005, 07:18:41 PM »
I do now.  ;)

For the Ksp values do you have to just remember them like molar masses or is there another way?

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Re:Lead precipitation
« Reply #5 on: July 16, 2005, 05:39:56 AM »
For the Ksp values do you have to just remember them like molar masses or is there another way?

It doesn't make sense to remember them. On the qualitative level you have solubility rules (and these are worth of remembering), on the quantitative level you can always check in tables.
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