123. Solving a chemistry problem

17. The determination of calcium in the prepared slag solution was carried out by the permanganometric method. To do this, 10 ml of a solution of oxalic acid with a concentration of c(1/2H2C2O4)=0.1016 mol/l was added to the analyzed solution, the excess of which was titrated with 5.20 ml of a solution of potassium permanganate with a concentration of c(1/5KMnO4)=0.1022 mol / l. Calculate the mass fraction (%, mass) of calcium in solution.