Chemistry - Surface Chemistry Question with Solution | TestHub

(A) CH₃(CH₂)₁₁OS₃Na is a surfactant (soap/detergent)

Surface tension decreases sharply with concentration due to adsorption at surface

After a point called CMC (Critical Micelle Concentration), it becomes constant

So graph in (A) is correct

(B) KCl is an electrolyte (non-surface active)

It increases surface tension slightly with concentration

So graph showing slight increase is correct

(D) the Critical Micelle Concentration (CMC), sodium stearate behaves as a normal strong electrolyte, and the osmotic pressure increases linearly with concentration. Above the CMC, the molecules aggregate to form micelles, which reduces the rate of increase in the number of independent particles in the solution. Consequently, the slope of the osmotic pressure versus concentration graph changes (decreases) after the CMC point, as qualitatively represented in the diagram.