Question

A compound with empirical formula CH was found by experiment to have a molar mass of approximately 78 g. What is the molecular formula of the compound?

Short answer

The molecular formula of the compound is C₆H₆, calculated by finding the empirical formula mass (13.02 g/mol), determining the ratio between the given molar mass (78 g/mol) and empirical formula mass (6), and multiplying the empirical formula (CH) by the ratio (6).

Step-by-step solution

Calculate the empirical formula mass

First, we need to find the empirical formula mass by adding the atomic masses of all the elements in the empirical formula. The atomic mass of carbon (C) is 12.01 g/mol, and the atomic mass of hydrogen (H) is 1.01 g/mol. The empirical formula mass is the sum of these atomic masses: Empirical Formula Mass = 12.01 g/mol (C) + 1.01 g/mol (H) = 13.02 g/mol

Calculate the ratio of the molar mass to empirical formula mass

Next, we need to determine the ratio between the given molar mass (78 g/mol) and the calculated empirical formula mass (13.02 g/mol): Ratio = Molar Mass / Empirical Formula Mass = 78 g/mol / 13.02 g/mol ≈ 6

Determine the molecular formula

Finally, to find the molecular formula, we multiply the empirical formula by the ratio we just calculated (6): Molecular Formula = (CH) x 6 = C₆H₆ Thus, the molecular formula of the compound is C₆H₆.