1 calories, and that of calcium hydroxide, when 1 atom of
calcium, 1 atom of oxygen, and 1 molecule of water unite together, is
+160.1 calories. [Footnote: When 1 atom of calcium, 2 atoms of oxygen,
and 2 atoms of hydrogen unite to form solid calcium hydroxide, the heat
of formation of the latter is 229.1 (cf. _infra_). This value is
simply 160.1 + 69.0 = 229.1; 69.0 being the heat of formation of water.]
Collecting the results into the form of a balance-sheet, the effect of
decomposing calcium carbide with water is this:
_Heat liberated._ | _Heat absorbed._
|
Formation of Ca(OH)_2 16O.1 | Formation of acetylene 58.1
| Decomposition of water 69.0
| Decomposition of carbide 3.9
| Balance 29.1
_____ | _____
|
Total 160.1 | Total 160.1
Therefore when 64 grammes of calcium carbide are decomposed by water, or
when 18 grammes of water are decomposed by calcium carbide (the by-
product in each case being calcium hydroxide or slaked lime, for the
formation of which a further 18 grammes of water must be present in the
second instance), 29.
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