Answer to Question #98487 in General Chemistry for Romana

Question

Lead is a highly poisonous metal. The mass percentage of lead in the 250 g aqueous solution was found to be 1.2×10−6% by extracting the lead with an excess of iodide and weighing the resulting PbI2. How many micrograms (μg) of lead iodide were measured?

Answer 1

Mass percentage of $Pb=1.2×10^{-6}$ %

100 g of solution contains 1.2×10^-6 g of Pb

250 g of solution contains 1.2×10^-6 ×250/100 g of $Pb = 3×10^{-6}g$

$no of moles of Pb = 3×10^{-6}/207.2=1.45×10^{-8}$

No of moles of $PbI_2=1.45×10^{-8}$

Mass of $PbI_2=1.45×10^{-8}×461.01=667.48×10^{-8}g$

$=6.674×10^{-6}g=6.67\mu g$ of lead iodide

(Answer)