C2(iii) - Using Ions in Solution 4.

Making Salts.

Most chlorides, sulphates and nitrates are soluble in water (the main exceptions are lead chloride, lead sulphate and silver chloride). Most oxides, hydroxides and carbonates are insoluble in water.

Making Soluble Salts from Insoluble Bases.

1) You need to pick the right acid, plus a metal carbonate or metal hydroxide, as long as it's insoluble. You can't use sodium, potassium or ammonium carbonates or hydroxides, as they are soluble (so you can't tell whether the reaction has finished).

2) You add the carbonate or hydroxide to the acid until all the acid is neutralised. (The excess carbonate or hydroxide will just sink to the bottom of the flask when all the acid has reacted.)

3) Then filter out the excess carbonate or hydroxide, and evaporate off the water and you should be left with a pure, dry salt.

E.g you can use copper carbonate and nitric acid to make copper nitrate:

CuCO3(s) + 2HNO3(ag) --------> Cu(NO3)2(aq) + CO2 + H2O(g) 

Making Insoluble Salts, Precipitation Reactions.

1) If the salt you want to make is insoluble, you can use a precipitation reaction…