Making salts from solutions LO: 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 salts Acid + 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 HNO 3(aq) + NH 4 OH (aq)  NH 4 NO 3(aq) + H 2 O H + (aq) NO 3 - (aq) + NH 4 + (aq) OH - (aq)  NH 4 + (aq) NO 3 - (aq) + H 2 O 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 precipitation Precipitation can be used for : Making pigments Treating water (Industrial Effluent) Testing for metal ions

An example of a precipitate reaction (NOTE STATE SYMBOLS) Pb(NO 3 ) (aq) + 2 KI (aq)  PbI 2(s) + 2 KNO 3(aq)