Question

Estimate the solubility and the activity coefficient of napthalene in a 30% methanol/ 70% water (v:v) mixture at 25 deg C

Answer 1

the free energy contributions of phase change to the overall free energy of solution are not affected by CMOS (with some exceptions in which the solvent changes the crystal structure of a solid). Hence, you need only estimate the effect of the CMOS on the activity coefficient. Use the  ratios given for naphthalene from tables in your book. f_v,_MeOH = 0.2 and f_{v,MeOH ⁼} 0.4 to estimate f_V,MeOH = 0.3 by interpolation, using the log-linear relationship Eq. Calculate first the log y::' values f_v,MeOH = 0.2 and 0.4, respectively.