How many atoms

Question

How many atoms are present in 406.4 g of lead (Pb)?

Answer 1

First, determine moles of lead present in 406.4 g of lead.

406.4 g Pb x  1 mole Pb/207.2 g = 1.961 moles Pb

 

Next, recognize that each mole of Pb contains Avogadro's number of atoms.  That is 6.02x10²³ atoms/mole.

1.961 moles Pb x 6.02x10²³ atoms Pb/mole Pb = 1.181x10²⁴ atoms Pb (to 4 significant figures)