Question

how many moles are in 2.31*10^21 atoms of lead

Answer 1

Hey there!:

Molar mass Lead  ( Pb ) = 207.2 g/mol

Therefore:

1 mole Pb --------------------- 6.02*10²³ atoms
? moles Pb -------------------- 2.31*10²¹ atoms

moles Pb = ( 2.31*10²¹ ) * 1 / ( 6.02*10²³ ) = 

moles Pb = ( 2.31*10²¹ ) / ( 6.02*10²³ ) = 

=> 0.00383 moles of Pb

Hope this helps !