Question

1) what is a salt? Give the names and formula of any two salts. Also name the acids and bases from which these salts may be obtained?

2) what is meant by hydrated and anhydrous salts.give examples.

3) write the names formulae and colours of any two hydrated salts.

Answer 1

•Any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation.


•Salt is formed by Reaction of acid and base.
•Example of 2 salts are : 1)NaCl (sodim chloride) 2) MgSO4(magnesium sulphate)

HCl(hydrochloric acid) + NaOH(sodium Hydroxide)→ NaCl (sodim chloride) + H2O

H2SO4(sulfuric acid) + Mg(OH)2 → MgSO4(magnesium sulphate) + 2H2O


What's the difference between hydrated salt and anhydrous s


Hydrated salts have water within their crystals when the crystals are formed from water; an anhydrous salt is where the crystal has had the water driven out. Water of crystallisation occurs for two reasons. The first, the ion has a strong electric field and it polarises water such that the water tends to pack around the ions. (When the field from a charge polarises another material, there is an attractive force between them, which is why rods charged electrostatically will pick up light particles, like small pieces of paper.) When the salt crystallises, the ions take the water with them, and adopt some structure where even more water might be incorporated. This is the reason that salts like sodium sulphate crystallise with a lot of water of crystallisation.

The second reason is mainly for transition metal ions, where the lone pairs of water molecules form weak dative bonds with the ion, by completing the outer electron shell. This usually changes the energy levels of the d electrons, which is shown by a colour change. An example is the cupric ion, reasonably shown with copper sulphate. Water bonds to it, and the ion goes blue. Stronger dative bonding, such as with ammonia, leads to a more intense blue. The hydrated ions form the crystal, but on heating, the crystal powders and the material goes white.


One of the most common examples is CuSO4.5H2O, or copper(II) sulfate pentahydrate. It’s blue in colour.

Another example is Glauber’s salt, or sodium sulfate decahydrate. It’s formula is Na2SO4.10H2O. It occurs as white or colourless crystals.