The formula for calculating the molecular formula given empircal formuls is expressed as;
[tex]molecular\text{ formula}=(empirical\text{ formula})_n[/tex]Substitute the given parameter to have:
[tex]\begin{gathered} 42=(CH_2)n \\ 42=(12+2(1))n \\ 14n=42 \\ n=\frac{42}{14} \\ n=3 \end{gathered}[/tex]Determine the molecular formula
[tex]\begin{gathered} molecular\text{ }formula=(CH_2)_3 \\ molecular\text{ }formula=C_3H_6 \end{gathered}[/tex]Hence the molecular formula of the given compound is C3H6