Physical Chemistry Nonideal Solutions Activity and Activity Coefficients The activity a; is more convenient to use in numerical calculations than ur (a)we can not determine absolute value of u; (more relative values) (b)A→>-0,asx->0. ca can be compared withxcar nd y with 1)to judge the degree of nonideal a.→)x.aSx.→1 y→>1,asx1>1
11 Activity and Activity Coefficients Nonideal Solutions (c) ai can be compared with xi (and i with 1) to judge the degree of nonideality. (a) we can not determine absolute value of i (more relative values). The activity ai is more convenient to use in numerical calculations than i . → −, → 0. i i (b) as x → , →1. i i i a x as x →1, →1. i i as x Physical Chemistry
Physical Chemistry Nonideal Solutions Standard States for Nonideal-Solution Components e Convention I uii=u(T, P) for all components (10.7)* Convention 1 is the same convention as that used for ideal solutions G Wiar is independent of the choice of standard state MTP,nj+ depends on the choice of standard state 11-7 a;=exp (10.3) RT every solution depends on the choice of standard state
12 Standard States for Nonideal-Solution Components Nonideal Solutions Convention I T P n j i i i n G , , o i ( , ) (10.7)* * , i T P o I i for all components Convention I is the same convention as that used for ideal solutions. is independent of the choice of standard state depends on the choice of standard state − = RT a o i i i exp every solution (10.3) depends on the choice of standard state Physical Chemistry
Physical Chemistry Nonideal Solutions Standard States for Nonideal-Solution Components e Convention I A,(, P) for all components (10.7) depends on the choice of standard state O 11=1 every solution RT (10.3) depends on the choice of standard state depends on the choice of standard state Therefore we denote aiyi,ui as convention I activities, activity coefficients and standard chemical potentials 13
13 Standard States for Nonideal-Solution Components Nonideal Solutions Convention I o i ( , ) (10.7)* * , i T P o I i for all components depends on the choice of standard state − = RT a o i i i exp every solution (10.3) depends on the choice of standard state i i i x a depends on the choice of standard state Therefore, we denote as convention I activities, activity coefficients and standard chemical potentials. o aI,i I,i I,i , , Physical Chemistry