Question

How many atoms are in 35.9 g of sodium sulfate (Na2SO4)?

Answer 1

number of moles of NaSO4 =
`(mass of compound)/(molar mass of compound)`

=
`(35.9)/(2(23) + 32 + 4(16))`

= 0.253 mol (3 s.f.)

0.253 mol =
`(number of atoms)/(avogadro's number)`

=
`(number of atoms)/(6.02(10^(23) ))`

thus, the number of atoms = 0.253 x
`6.02(10^(23))`

= 1.52 ×
`10^(23)`