The empirical formula of a compound is ch. it's molar mass is 52.07 g/mole. what is its molecular formula

For this item, we find first the mass of the compound with the empirical formula. That is,
                             molar mass = 12 (for C) + 1 (for H)
                                                   = 13 g/mole
Then, we divide the given mass of the molecular formula by the mass of the empirical formula. 
                                    n = 52.07 / 13 = 4
Therefore, the molecular formula is C₄H₄.