163 combining the first and the second law relations

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: the second-law relations for this system gives dQ P dV dU dQ dS T dU P dV T ds 0 (162) Chapter 16 The differential of the Gibbs function (G ture and pressure is 1dG2 T,P dH 1dU dU T dS P dV P dV S dT V dP2 | 795 H TS) at constant tempera- G 0 T dS S dT 0 (163) dG < 0 dG = 0 dG > 0 T dS From Eqs. 162 and 163, we have (dG)T,P 0. Therefore, a chemical reaction at a specified temperature and pressure proceeds in the direction of a decreasing Gibbs function. The reaction stops and chemical equilibrium is established when the Gibbs function attains a minimum value (Fig. 164). Therefore, the criterion for chemical equilibrium can be expressed as 1dG2 T,P 0 (164) Violation of second law 100% reactants Equilibrium composition 100% products A chemical reaction at a specified temperature and pressure cannot proceed in the direction of the increasing Gibbs function since this will be a violation of the second law of thermodynamics. Notice that if the temperature or the pressure is changed, the reacting system will assume a different equilibrium state, which is the state of the minimum Gibbs function at the new temperature or pressure. To obtain a relation for chemical equilibrium in...
View Full Document

This note was uploaded on 06/15/2009 for the course MAE 3311 taught by Professor Hajisheik during the Summer '08 term at UT Arlington.

Ask a homework question - tutors are online