Question

Assuming that at 298 K the CMC for a certain surfactant is 6 X 10^-3 M and that its mean aggregation number is 70. The bulk surfactant concentration is 0.08 M. Estimate ΔG^o for micellization if the molecular weight of the surfactant is 326 g mol-I. If the enthalpy of micellization is 8 kJ mol-I, find the entropy change when 1 mol of micelles forms from 70 moles of monomers

Answer 1

Given: T = 298 K

CMC = 0.006 M

Mean aggregation number = 70

Bulk concetration = 0.08 M

Molecular Weight = 326 g/mol

Enthalpy = 8 kJ/mol

To find: ,

Solution:

= RTln(CMC)

= 8.314 * 298 * ln(0.006)

= 8.314 * 298 * (-5.11)

= - 12.7 kJ/mol

Now,

= [8 - (- 12.7)] / 298

= 0.069 kJ/mol/K