PPT Slide

12

• Most physical and chemical changes occur under virtually constant  atmospheric pressure: in an open flask, in a lake, in an organism, etc.

• A thermodynamic variable called enthalpy takes constant pressure  into account.

A gas expands against a constant pressure:

PV work done = P x _V or P(Vfinal ñVinitial)

The work done by an expanding gas on the surroundings is w = ñ P_V

Concept 6-5 The meaning of enthalpy and the relation between DE and DH.

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