Question

A compound containing carbon and hydrogen is 85.71% carbon by mass. If the molar mass of the compound is 84.00 g/mol, what is the molecular and empirical formula of the compound?

Answer 1

Percentage of Carbon = 85.71%

Percentage of Hydrogen = 100 - 85.71 = 14.29 %

C atoms = 85.71 / 12 = 7.1425

H atoms = 14.29 / 1 = 14.29

simple number = for C = 7.1425 / 7.1425 = 1

                               for H = 14.29 / 7.1425 = 2.00

empirical formula = CH2

number of empirical units = molecular mass / empirical mass = 84 / 12 = 7

MOlecular formula of the compound = C7H14