20. Solving a chemistry problem

56. Calculate the molar concentration of the equivalent of a solution of perchloric acid in glacial acetic acid if, during photometric titration with this solution, a sample of diphenylguanidine M (C13H13N3) = 211.28 g / mol weighing 0.0696 g in glacial acetic acid with an indicator of tropeolin 00 at λ = 540 nm, the following results were obtained:
V(HClO4). ml 0 1.0 2.0 2.4 2.8 3.2 3.4
A 0.070 0.070 0.080 0.090 0.100 0.130 0.170
V(HClO4). ml 3.6 3.7 3.8 4.0 4.2 4.4 4.8 5.0
A 0.330 0.670 1.07 1.07 1.07 1.07 1.07 1.07