Precipitation Reactions
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Transcript Precipitation Reactions
Precipitation Reactions
Experiment 7
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Lab #7 Precipitation Reactions
Goals of the Lab
Learn
about Precipitation Reactions
Understand ions in a solution
Identify new compounds formed in a
reaction
Write equations for reactions
Complete
Net
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Ionic
Lab #7 Precipitation Reactions
Aqueous solutions: Ions dissolved in water
Barium Nitrate
Ba(NO3)2
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Ba2+ + 2 NO3-
Sodium Sulfate
Na2SO4
Lab #7 Precipitation Reactions
2Na+ + SO42-
Add the 2 aqueous solutions together:
The
ions are able to intermingle
There may be an attraction, that results in a
reaction (energetically favorable)
Possible Reactions include
Formation of a gas
Formation of water
Formation
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of a Precipitate (ppt.)
Lab #7 Precipitation Reactions
How do I know what formed??
In reaction A you started with Barium Nitrate and
Sodium Sulfate
There is a reaction as evidenced by the white
precipitate
What is it?
Barium Sulfate OR Sodium Nitrate?
You must do some detective work
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Lab #7 Precipitation Reactions
Barium Sulfate OR Sodium Nitrate?
Is there any place else that
BaSO4 could have formed?
Is there any place else
where NaNO3 could have
formed?
YES
Yes
In Reaction B
In Reaction G
What happened in each reaction?
If an ion pair forms a ppt. in one reaction, assume they will get
together any chance they get!
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Lab #7 Precipitation Reactions
The ‘intermingling’ has caused a
Other ‘non-reacting’ ions remain
reaction
soluble…. Still in solution
The barium ions and
the sulfate ions have an
attraction to each other,
they form a solid
compound and “fall”
out of solution as a
precipitate
Lab #7 Precipitation
Reactions
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Data Analysis
Reaction
A
Solution Pairs
Yielding
Precipitates
Formulas of
Possible
Precipitates
Reasons for Choice of
Precipitate
Ba(NO3)2
NaNO3
Na2SO4
BaSO4
In rxn B, Ba2+ and
SO42- formed a ppt.
when mixed.
In rxn G, Na+ and NO3were both present with
no ppt. formed.
B
Lab #7 Precipitation
Reactions
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Complete and
Net Ionic Equations
Lab #7 Precipitation
Reactions
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Lab #7 Precipitation Reactions
Sometimes parts of the equation do nothing
but sit and watch.
Spectators
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Lab #7 Precipitation Reactions
Complete ionic vs. net ionic
Sodium sulfate + Barium Chloride react to form Solid barium sulfate
and Sodium chloride
2 Na+ (aq) + SO42- (aq) + Ba2+ (aq) + 2 Cl- (aq)
BaSO4 (s) + 2 Na+ (aq) + 2 Cl- (aq)
NaCl is a strong electrolyte, so it does not combine to form a solid
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Lab #7 Precipitation Reactions