28. Solving a chemistry problem

23. For the polarographic determination of zinc cations Zn2+ in the analyzed solution of zinc sulfate with a volume of 50 ml, containing additives of gelatin (to suppress polarographic maxima) and potassium chloride (supporting electrolyte), 20 ml of this solution were taken, placed in a temperature-controlled polarographic cell and a current was passed through the solution hydrogen gas (to remove dissolved oxygen). Conducted polarography and received a polarographic wave with a height of 12 units.
Prepared a standard solution. To do this, a few drops of gelatin solution were added to 10 ml of a zinc sulfate solution with a zinc cation content of 0.5 mg/ml, and the volume of the solution was brought to 50 ml by adding a potassium chloride solution. Conducted polarography 20 ml of the standard solution under the same conditions in which polarography analyzed solution, and received a polarogram with a polarographic wave height of 10 units. Calculate the mass of zinc cations in the analyzed solution using the method of standard solutions.