141. Solving a chemistry problem

141. Solving a chemistry problem

7. To determine lead in zinc ore by the addition method, a sample of ore weighing m g was dissolved in a mixture of acids, iron (III) was reduced, gelatin was added, and the solution was diluted to 200.0 ml. An aliquot with a volume of 20.00 ml was placed in an electrolyzer and the height h1 of the polarographic wave was measured at E = –0.45 B (NCE). Under these conditions, ions of copper, zinc, cadmium do not interfere with the determination of lead. After adding a standard VCT solution ml of 0.0020 M Pb (NO3)2 to the electrolyzer machine, the wave height h2 was obtained.
Calculate the mass fraction (%) of lead in the ore for the following options:
Option 1
m, g 1,000
h1, mm 22,0
Vst, ml 10,00
h2, mm 42,0

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