Oxides of metals are called base. They are soapy to touch.
Those compounds which release hydroxyl ion (Anion) in their aqueous solution are called base.
NaOH→Na+ + OH-
Ca(OH)2→ Ca+++ 2OH-
Mg(OH)2 → Mg++ + 2OH-
Alkali: Some metallic oxides (base) give their respective hydroxide when dissolved in water. Such water-soluble bases are called alkalis.
On the basis of strength, bases are of two types:
Similarly, on the basis of their origin, bases are of two types:
Fig: Formation of hard water
Copper sulphate is prepared by the reaction between an insoluble base and acid. At first, some copper oxide is added to dilute sulphuric acid. On warning, it dissolves and the solution turns blue. More copper oxide is added until no more dissolve. The excess of solid is removed by filtering. This leaves a blue solution of copper sulphate. The solution is heated to evaporate some of the water content. Then it is left to cool. Blue crystals of copper sulphate start to form.
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