Can you explain "all alkalies are bases, but all bases are not alkalies."

Expert Answers

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Before I delve into that answer, let me basically define what a base and an alkali, are.

A base is, very simply, a substance which reacts with an acid, to form a salt and water.

Acid + Base --> Salt + Water

An alkali would, very simply, mean a water-soluble base, something which gives OH-(hydroxyl) ions when it dissolves in water.

Cu(OH)2 --> Cu2+ + 2OH-

Clearly, all hydroxides like this one, Cu(OH)2 (Copper Hydroxide), is a alkali, and a base as well, because it reacts with an acid, to form salt and water.

Cu(OH)2 + 2HCl --> CuCl2 + 2H2O.

The thing is that bases which are oxides such as Copper(II) Oxide CuO, are not water soluble, and thus don't give hydroxyl ions when dissolving in water - they don't dissolve in water.

CuO + 2HCl --> CuCl2 + H2O.

BUT,

CuO -->(No OH- ions).

THUS, in conclusion, all alkalis are bases, but all bases (except hydroxides) are NOT alkalis.

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