0731. Solving a chemistry problem

2. Determine at what concentration of iso-valeric acid the surface tension of its aqueous solution at 25 C will be equal to 60 mN/m, if the dependence of surface tension on concentration is expressed by the Shishkovsky equation with constants B = 16.7 * 10-3 J/m, A =21.5 l/mol. Calculate the area occupied by one acid molecule in a close-packed surfactant monolayer at the solution/air interface. The surface tension of water at this temperature is 71.96 mN/m.