Here's how to determine the molecular formula of a compound with the empirical formula CH2 and a molar mass of 84 g/mol:

1. Find the empirical formula mass:

* C: 12.01 g/mol

* H: 1.01 g/mol

* Empirical formula mass of CH2 = 12.01 + (1.01 x 2) = 14.03 g/mol

2. Determine the ratio of molecular mass to empirical formula mass:

* Molecular mass / Empirical formula mass = 84 g/mol / 14.03 g/mol ≈ 6

3. Multiply the subscripts in the empirical formula by the ratio:

* CH2 x 6 = C6H12

Therefore, the molecular formula of the compound is C6H12.