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Making salts from solutionsLO:
Describe what happens during a precipitation reaction (D)
Explain how an insoluble salt can be formed (C)
Explain in detail what precipitation is in terms of the ions involved (B)
Make conclusions about a reaction and it’s products based on your knowledge of precipitation reactions (A/A*)
Starter
Define what is meant by ‘soluble’ and ‘insoluble’.
Making soluble saltsAcid + Alkali a Salt + Water
Sulphuric acid + Sodium Hydroxide
What can we use to detect when the acid has completely reacted ?
Ammonium salts can be made by reacting ammonium hydroxide with an acid.
Nitric acid + Ammonium Hydroxide Ammonium Nitrate + Water
HNO3(aq) + NH4OH(aq) NH4NO3(aq) + H2O
H+(aq)NO3
-(aq) + NH4
+(aq)OH-
(aq) NH4+
(aq)NO3-(aq) + H2O
These are usually made for use as a _____________.
The salt is in water and can be obtained using ___________.
The ammonia is added in slight excess and during the evaporation of the water it also evaporates.
Making insoluble salts
What is a PRECIPITATE ?
A precipitate is what is produced when two solutions of soluble chemicals are mixed to produce a chemical that is insoluble.
Because it is insoluble a solid is seen to form in the liquid (or it goes cloudy).
This is a precipitate.
Uses of precipitationPrecipitation can be used for :
Making pigments
Treating water (Industrial Effluent)
Testing for metal ions
An example of a precipitate reaction (NOTE STATE SYMBOLS)
Pb(NO3)(aq) + 2 KI(aq) PbI2(s) + 2 KNO3(aq)
http://www.youtube.com/watch?v=4U-DgdWPKyo