4
Another type of substance with strong acidic character is an
acid chloride. Two examples and their reactions with water are
boron trichloride, reaction (12),
BCl3 + 3H2O —> H3BO3 + 3HCl
and acetyl chloride, reaction (13).
CH3COCl + H2O —> CH3CO2H + HCl
These are often termed hydrolysis reactions, as in the
reaction of an ester with water, for instance ethyl acetate,
reaction (14).
0 0
H3CCOC2H5 + H2O —> H3CCOH + HOC2H5
A hydrolysis reaction of a different sort is that of calcium
carbide, used in the production of acetylene, reaction (15).
CaC2 + 2H2O —> Ca(OH)2 + C2H2
Water reacts with a variety of substances to form solid com-
pounds in which the water molecule is intact, but in which it
becomes a part of the structure of the solid. Such compounds
are called hydrates, and are formed frequently with the evolu-
tion of considerable amounts of heat. Examples range from
the hydrates of simple and double salts, calcium chloride
hexahydrate, CaCl2 · 6H2O, and ammonium aluminum alum,
NH4Al(SO4)2 · 12H2O, to the gas hydrates which are stable only
at low temperatures, for example, chlorine hydrate, Cl2 · 6H2O,
and xenon hydrate, Xe · 6H2O.
Water (continued)
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