Question

Calculate the number of molecules in 16 grams of sulphur dioxide

Answer 1

$moles = \frac{given \: mass}{molar \: mass} \\ moles = \frac{no. \: of \: molecules}{avogadro \: no.} \\ \frac{given \: mass}{molar \: mass} = \frac{no. \: of \: molecules}{avogadro \: number}$
Molar mass of sulphur dioxide–» 32+16×2
=64

so,
$\frac{16}{64} = \frac{no. \: of \: molecules}{6.022 \times {10}^{23} } \\ no. \: of \: molecules = \frac{6.022 \times {10}^{23} }{4}$
Hope it will help you!!