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### Topic: Precipitation Problem  (Read 7097 times)

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#### 113zami

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##### Precipitation Problem
« on: April 15, 2009, 07:45:38 PM »
I took a chem test on line and guessed on this problem and got it right.. but when I reviewed it now .. I don't understand it

http://mysowar.wordpress.com/files/2009/04/percipetate.jpg

First of all I don't understand where it says :

This sequence shows (assuming equal anion concentrations, as must be done here) that PbCO3 is less soluble than PbI2, and PbI2 is less soluble than PbSO4.

How can we make the above assumption when we don't know how fast each precipitate precipitated compared to the others ?

I also don't understand
if PBCO3 is less soluble than PBI2 and PBSO4.. how can Co3(2-) be the first to precipitate ?

« Last Edit: April 15, 2009, 07:57:40 PM by 113zami »

#### Borek

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##### Re: Precipitation Problem
« Reply #1 on: April 16, 2009, 03:13:07 AM »
How can we make the above assumption when we don't know how fast each precipitate precipitated compared to the others ?

Based on the composition of solutions used.

Quote
I also don't understand
if PBCO3 is less soluble than PBI2 and PBSO4.. how can Co3(2-) be the first to precipitate ?

I don't understand what you don't understand. How do you expect more soluble salt to precipitate first and leave less soluble salt inthe solution? It doesn't make logical sense.
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#### AWK

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##### Re: Precipitation Problem
« Reply #2 on: April 16, 2009, 04:53:23 AM »
The sequence of reaction is not correct. The highest solubility show PbI2, not PbSO4.
AWK