Solubility is the ability to dissolve in a solvent.

The solubility of salts is important       (a) to separate a salt from a mixture of salts       (b) to prepare a salt sample       (c) to identify cations and anions through     qualitative analysis  

WHAT IS SOLUBILITY??

•A soluble salt is a salt that dissolves in water at room temperature.

•Soluble salts in water include:        (a) all nitrates and ethanoates        (b) all sodium, potassium and ammonium salts        (c) all chlorides except  lead (II) chloride (PbCl2), silver chloride (AgCl), and mercury chloride (HgCl2)             * Lead (II) chloride dissolves in hot water but not in

cold water* C-PAH (include I-PAH & B-PAH)

          (d) all sulphate except lead (II) sulphate (PbSO4), calcium sulphate (CaSO4) and barium sulphate (BaSO4)

* S-PCB          (e) lead halides that is lead (II) chloride (PbCl2), lead (II) iodide (PbI2), lead (II) bromide (PbBr2), only dissolve in hot water

SOLUBLE SALTS

• Soluble salts can be prepared and produced through four type of reactions as below:

 (a) Reaction between acid and alkali     (b) Reaction between acid and base                        (c) Reaction between acid and reactive metal    (d) Reaction between acid and metal carbonate                   

PREPARATION OF SOLUBLE SALTS

1. The reaction involved in preparing soluble salts type Na+/K+/NH4

+ is called neutralisation reaction

METHODS OF PREPARING SOLUBLE SALTS

• Examples of the reactions are:                                              •         KOH (aq) + HNO3 (aq) → KNO3 (aq) + H2O (l)• NaOH (aq) + HCl (aq) → NaCl(aq) + H2O (l)• 2NH3 (aq) + H2SO4 (aq) → (NH4)2SO4 (aq)• 2NaOH (aq) + H2SO4 (aq) → Na2SO4 (aq) + H2O (l)

NEUTRALISATION REACTION

2. Soluble salts that is exclude of sodium, potassium and ammonium salts The procedures involved in preparing this type of soluble salts is shown

as below:

For example is the preparation of zinc sulphate, ZnSO4:

        (a) Zn (s)    +    H2SO4 (aq)     →      ZnSO4 (aq)    +    H2 (g)              (metal   +    acid                →      salt    +    hydrogen)

         (b) Zn0 (s)    +    H2SO4 (aq)        →      ZnSO4 (aq)    +    H2O(l)              (oxide metal   +    acid     →       salt    +    water)

         (c) Zn(OH)2 (s)    +    H2SO4 (aq) →      ZnSO4 (aq)    +    2H2O(l)              (hydroxide metal   +    acid   →      salt    +    water)

         (d) ZnCO3 (s)    +    H2SO4 (aq)   →      ZnSO4 (aq)    +    H2O(l)    +    CO2 (g)               (carbonate metal   +    acid  →      salt    +    water    +    carbon dioxide)