I need help calculating atoms from mass. please!?

Question

find the number of O atoms in .291g CuSO4.

thanks for the help

Answer 1

Cu = 63.5

S =  32

O =  16

CuSO4 = 159.5

0.291g CuSO4(please write the zero before the decimal. It is hard to see by itself, which can lead to BIG errors) = 0.291/159.5 = 0.0018182 moles of copper sulfate

One mole CuSO4 contains 4 moles of oxygen atoms

0.0018182 moles CuSO4 contains 0.007273 moles of oxygen atoms.

Avogadro's Lawtells us that the number of elementary entities (atoms, molecules, ions or other particles) in one mole of a substance is 6.022 x 10^23

Number of atoms in 7.273 x 10^-3 moles of oxygen atoms =

( 6.022 x 10^23) x (7.273 x 10^-3) = 4.380 x 10^21