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.

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