How many aluminum atoms are there in 319 g of al2s3

The number of aluminium atoms that are in 319 g of Al2S3 is calculated as follows

find the total moles of Al2s3

=moles = mass/molar = 319 g / 150 g/mol = 2.13 moles

since there are two atom of Al in Al2S3 the moles of Al = 2 x 2.13 = 4.26 moles

by use of Avogadro law constant 1 mole = 6.02 x10^23 atoms

what about 4.26 moles of Al

= 4.26 moles x (6.02 x10^23) = 2.56 x10^ 24 atoms