## Chemistry: A Molecular Approach (3rd Edition)

$0.0790g\ SO_{3}$
Divide the number of molecules by Avagadro's number to get the number of moles. Multiply this number by the molar mass of the compound to get the mass of the sample. $5.94\times10^{20}molecules\ SO_{3}\times\frac{1mol\ SO_{3}}{6.022\times10^{23}molecules\ SO_{3}}\times\frac{80.066g\ SO_{3}}{1mol\ SO_{3}}= 0.0790g\ SO_{3}$