117. Solving a chemistry problem

117. Solving a chemistry problem

To determine lead in the ore, a 5.000 g sample of the ore was taken. After dissolving it in acid, the Pb 2 ion was precipitated in the form of PbСgO4, the precipitate was filtered, washed and dissolved in a mixture of HCl and KI (reaction equation). The iodine isolated during this reaction was titrated with a 0.5000 N solution of Na2S2O3 and 42.00 cm3 of it was consumed. What percentage of lead does the ore contain?

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