Calculate the mass fraction of formic acid in a sample weighing 2.5 g diluted with water in a volumetric flask up to 150 ml if 9.15 ml of potassium permanganate titrant (c1/zT) = 0.0025 mol/L. Write: a) reaction scheme; b) factors of equivalence of participants of reaction; c) the expression of the law of equivalents for this reaction; d) type of chemical reaction (titration method); e) indicator for determination of equivalence point (choice to explac)