preparation of salts

book: chemistry matters, GCE, o level (2nd edition)
chapter: 12, salts.

Salt
an ionic compound (contain a cation and an anion) 
e.g: NaCl

salts are prepared according to their solubility. 

check the solubility of the salt: 
if it dissolves in water, it creates an aqueous solution
if it does not dissolve in water, it remains in its solid state. 

so, if it does not dissolve, the method used to prepare it will be the precipitation method. (not covering this)
however, if it does dissolve, we can prepare the salt by using the acidic reactions, which are: 
acid + metal = salt + H₂
acid + metal carbonate = salt + H₂O + CO₂
acid + base or metal oxide/metal hydroxide = salt + water
(alkali's are metal oxides / metal hydroxides) 

once you choose your acidic reaction, check the solubility of both the reactants.
if both reactants are soluble in water, then use the titration method.
if both the reactants are NOT soluble in water, then it will be reacting with excess metal/base/carbonate.

Method 1: both reactants are not soluble: 
in this method, the metal, base or carbonate you will be using, should be in excess, so that when the salt is formed, it is not contaminated with the acid.
and obviously, the metal, base or carbonate you will be using should be insoluble in water so that it is later removed by filtration. 
this method is not suitable for all metals as some metals are highly reactive to the point where it is dangerous. e.g: sodium.

Investigation 1: preparing zinc sulfate. (acid+metal) - same for the others.
1) fill a beaker with dilute sulfuric acid, while constantly stirring, add zinc powder until no more reaction is being observed. 
2) filter the mixture and collect the filtrate. (zinc sulfate solution) 
3) in an evaporating dish, heat the filtrate till saturation point.
4) let the saturated solution cool, and let the salt crystalize. 
5) filter to collect the crystals, then wash them with distilled water to remove impurities, dry them and zinc sulfate is formed. 

Method 2: both reactants are soluble, this method is called titration. 
all the materials should be soluble, if any of the material is excess, it can not be removed by filtration later on and so the salt produced will be impure, therefore the volume of each material should be exact.

Investigation 2: preparing sodium nitrate. 
involves 2 parts: titration, and preparation of a pure sample of sodium nitrate. 
a) titration:
1) fill a burette with nitric acid, note the reading as V₁ 
2) using a pipette, add 25.0cm₃ of sodium hydroxide to a conical flask
3) add 1-2 drops of methyl orange, the solution should turn yellow.
4) while swirling the flask, add in the nitric acid through the burette until the solution turns orange. note the final reading on the burette as V₂
5) V₂-V₁= volume of acid required for complete neutralization. 

b) prepare a pure sample of sodium nitrate.
1) pipette 25.0cm₃ of sodium hydroxide in a conical flask. do not add any indicator, as it will make the salt impure.
2) add (V₂-V₁)cm₃ nitric acid from the burette.
3) heat the solution till saturated, let the solution cool down
4) filter, wash and dry the crystals, and sodium nitrate salt is formed. 


soluble salts:                                               insoluble salts:
all sodium salts                                              silver chloride
all potassium salts                                          lead chloride
all ammonium salts                                        barium sulphate
all nitrates                                                       lead sulphate
all chlorides                                                    calcium sulphate 
all sulphates                                                    all carbonates 
sodium carbonate
potassium carbonate
ammonium carbonate



for further clarity, i recommend watching cognito's videos on this topic :)