To find the molecular formula from the empirical formula, you need to find a multiple (x) that will give you the molar mass of the compound which in the question is 50.48 g/mol.
If CH₃Cl is the empirical formula
molar mass of empirical formula = (12 × 1) + (1 × 3) + (35.5 × 1) g/mol
= 50.5 g/mol
let x = multiple
let molecular formula = Cₓ H₂ₓ
multiple = molecular mass ÷ empirical mass
= 50.5 g/mol ÷ 50.48 g/mol
≈ 1
If molecular formula = Cₓ H₃ₓ Cl
then molecular formula = C₍₁₎ H₃₍₁₎ Cl₍₁₎
= CH₃Cl
