4. The surface tension, y, of an aqueous solution of a certain surfactant is related to the bulk concentration, c, at 18C by the equation y = Y.-29.8Inc mNm where y. is the surface tension of pure water. Using Gibbs adsorption equation, calculate the surface excess concentration, r, of the solute in molesm? and area per molecule. 5. The following surface tension were measured for the aqueous solutions of the non-ionic surfactant CH3(CH2),(OCH2CH2)-OH at 25C. Determine the critical micelle concentration (cmc) and the area occupied by each surfactant molecule at the critical micelle concentration (cmc). c/mM y/mNm2 0.01 0.03 63.9 56.2 0.1 47.2 0.2 0.5 41.6 34.0 0.8 1 2 3 30.3 29.9 29.6 29.5