The following equation denotes the surface tension () for an anionic surfactant with a 14-carbon chain in pure water at 25C with the concentration C in units of mol/L:

a) Determine the pC20 value, where C20 is the concentration required to reduce the surface tension of pure solvent or solution by 20 mNm¹. The pC20 value is also known as "surfactant efficiency"

b) If the surface tension of a solution of this surfactnat with a concentration of C = 0.25 mol/L is measured to be 29.0 mN/m, estimate the CMC of the surfactant.

c) If the surfactant above were exchanged for the 16-carbon member of the same series, describe how the surface tension data would change and give a numerical estimate of the new pC20 value.

o = 72.2 15.9 In (1 + (2.764 x 104) C) o = 72.2 15.9 In (1 + (2.764 x 104) C)