The empirical formula for a compound is ch2. its molar mass is 140.1 g/mol. what is its molecular formula?

The empirical formula CH₂ has a mass [(12 × 1) + (1 × 2)] = 14 g/mol

If the empirical formula is 14 g/mol,
and the molecular formula is ~140 g/mol

Then the multiple is = 140 g/mol ÷ 14 g/mol 
                                = 10

Therefor the molecular formula is 10(CH₂) = C₁₀H₂₀