140. Solving a chemistry problem

104. The analyzed solution of methylamine CH3NH2 with a volume of 20.00 ml was diluted in a volumetric flask to 100.0 ml, then 10.00 ml of the resulting solution was titrated potentiometrically with 0.1000 N HCl solution. Determine the concentration (mol / l) of the starting methylamine solution according to the following data - table 40.

Table 40

V, ml
(HCl) 10.0 12.0 14.0 14.5 14.9 15.0 15.1 15.5 16.0
pH 10.40 10.12 9.56 9.28 8.42 6.02 3.52 2.85 2.55