Question

a 25.00 ml sample of a lead ion solution gave 0.2375 g of lead chromate. What is the concentration on lead in the solution in mg/l.

Answer 1

lead chromate = PbCrO4

Moles of Pb in 1 mole of lead chromate = 1 mole

Given,

Mass of lead chromate = 0.2375 g

Molar Mass of lead chromate = 323.2 g / mol

=> Moles of lead chromate = 0.2375 / 323.2 = 7.35 x 10^-4 moles

=> Moles of Lead ion in the solution = 7.35 x 10^-4 moles

Molar Mass of Pb = 207.2 g / mol

=> Mass of 7.35 x 10^-4 mole Pb = 7.35 x 10^-4 x 207.2 = 0.1523 g = 152.3 mg

Volume of solution = 25 mL = 0.025 L

Concentration (mg / L) = Mass (mg) / Volume (L)

=> Concentration of lead ion in solution = 152.3 / 0.025 = 6092 mg / L (milligram per liter)