Precipitation

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Section 15.7 Precipitation Qualitative Analysis
So far solids dissolving in solutions Now--- Loo
k at formation of solid from solution That is,
the REVERSE Process.
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Section 15.7 Precipitation Qualitative Analysis
Calculate Q, ion product Like Ksp , but use
initial conc. rather than equilibrium conc.
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CaF2 (s) ? Ca2 (aq) 2 F- (aq) Q
Ca2o F-o2 Q Ion Product
moles/L CaF2 (s) not included in Q.
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If Q gt Ksp , then precipitation occurs.
If Q lt Ksp , then no precipitation occurs.
If precipitation occurs, you can also
do calculations to determine equilibrium conc. in
solution after precipitation.
Lets do 97 99
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Selective Precipitation
Method to separate a mixture of ions in
which reagents are added to precipitate single
ions or small groups of ions
Example Solution of Ba2 and Ag ions
Add NaCl only AgCl precipitates, Ba2 still in
solution
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Qualititative Analysis Scheme
See Fig 15.11 15.12 on page 771 Read pages
770-772
Sulfide ion is often used to separate metal ions.
See page 770.
Lets do 101