9+ GENERAL CONDITIONS OF EQUILIBRIUM, chap.
where /x denotes the heat absorbed when a gram-molecule of ammonium chloride is transformed into a mol of ammonia and a mol of hydrochloric acid. The condition for the applicability of this equation is that the pressure remains constant ; if the change takes place at constant volume, then, as in the case of solutions, we may introduce the concentra- tions (C) instead of the pressures, and obtain —
d(ln Ci + In C;^^ In Ci) ^ _^ (IT ~ BT^'
a In —7-7 —
or - a — /*
��(IT BT^
We know that at constant temperature —
��a
��or integrated —
��We therefore have for the change of K with change of temperature —
(IT BT^'
where M is a constant, or finally —
In general, for a reaction which takes place according to the chemical equation —
mP + nQ + oB + , . . =. fS -k- gT + hV + . . . we have the equilibrium equation —
v a n .s r r
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