water
A colorless or faintly blue-green liquid (H
2 O). Molecules of water enter into the
constitution of many crystalline salts, e.g.,
alum—K 2 SO 4 .Al
2 (SO 4 ) 3 . 24H
2 O, in which they may be reversibly
held. The outstanding chemical reactions of water
are: 1) its reaction with certain metals, e.g.,
Na, Ca, Fe, more or less easily, with the
liberation of hydrogen, such as, Na + H
2 O → NaOH + H; 2) its reaction
with oxides of non-metals, e.g., with SO
3 to form acids, such as, SO
3 + H 2 O → H
2 SO 4 ; 3) with halides of
nonmetals, to form hydrogen halides and an
oxyacid, such as PCl 3 + 3H
2 O → H 3 PO
3 + 3HCl; 4) with dissolved salts of
weak acids or weak bases, forming solutions with
an alkaline or acid reaction (hydrolysis), such as
Na 2 CO 3 + H 2 O
⇌ NaOH + NaHCO 3 ; and 5) with
coke at high temperature to form water gas, C + H
2 O → CO + H 2 . (235 )
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