Question

B Quantitative Analysis 464 Cerlun 14424 Tar pEN Moln Thu Ac Th Pa Np Pu Am Cm Bk Cf 101 Md No Es Fm 24064 na1 Lead is a highly poisonous metal. The mass percentage of lead in the 250 g aqueous solution was found to be 1.2 x 100% by extracting the lead with an excess of lodide and weighing the resulting Pbl. How many micrograms (ug) of lead iodide were measured? Your answer should have two significant figures (round to the nearest tenth) Provide your answer below: micrograms

Answer 1

Mass of Pb = 1.2*10^-6 % of 250 g

= 1.2*10^-6 * 250 / 100

= 3.0*10^-6 g

Molar mass of Pb = 207.2 g/mol

mass(Pb)= 3.0*10^-6 g

use:

number of mol of Pb,

n = mass of Pb/molar mass of Pb

=(3*10^-6 g)/(2.072*10^2 g/mol)

= 1.448*10^-8 mol

This is number of moles of Pb

one mole of PbI2 contains 1 moles of Pb

use:

number of moles of PbI2 = number of moles of PbI2 / 1

= 1.448*10^-8 / 1

= 1.448*10^-8

Molar mass of PbI2,

MM = 1*MM(Pb) + 2*MM(I)

= 1*207.2 + 2*126.9

= 461 g/mol

use:

mass of PbI2,

m = number of mol * molar mass

= 1.448*10^-8 mol * 4.61*10^2 g/mol

= 6.675*10^-6 g

= 6.68 ug

Answer: 6.68