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Preparation of Salts

There are 5 methods in preparation of salts. 

1) Acid + Base --> SALT + Water

2) Acid + Carbonate --> SALT + CO2 + Water

3) Acid + (Reactive) metal --> SALT + H2

4) Reaction of 2 soluble salts

5) Titration method

As for method 1, as we know that the general equation for neutralization is by adding ACID and BASE together to form SALT  and Water. As the salt that is dissolved in aqueous form is ionic bonded, it has a very high melting point. Therefore, as water is evaporated at 100oC,  the left over will be solid SALT, which is making use of evaporation process. 

As for method 2, Acid reacts with carbonates to form CO2 gas, SALT and Water.  For example, when marble chips (CaCO3) reacts with HCl, CaCl2 salt will be formed as CO2 gas is evolved and water is evaporated away. Therefore, this method is considered as one of the easiest method to obtain salt from Acid reaction.

As for method 3, Acid reacts with metals to form metal and H2 gas. Since H2 gas is evolved, one will have aqueous form of metallic salt. We can evaporate the water in the aqueous solution to obtain the salt.

As for method 4, if 2 soluble salts are reacted with each other, they displace out each other. Hence, forming a precipitate salt and a soluble salt. In this case, filter to obtain the precipitate salt and evaporate to obtain the residue solution to obtain the solute.

As for method 5, it still goes back to the ACID + BASE theory. For example, in this case fixed volume of HCl is used and excess amount of NaOH is used in the titration process. For example, 25 cm3 of HCl and excess amount of NaOH is used. Phenolphthalein is added to the HCl solution. NaOH is titrated  till the color of the phenolphthalein changes to light pink. Repeat the experiment the same times with the known volume of the HCl and NaOH to ensure that the neutralization point occurs. From there, we can evaporate the solution to obtain the salt.