Question

A compound contains 69.94 percent iron and 30.06 percent oxygen. What is its molecular formula if the molar mass of the compound is 199.55 grams per mole?

Answer 1

Determine the empirical formula

                      Fe                      O

moles       69.9/56                     30.06/16

  ratio        1.248/1.248                        1.8788/1.248

                          1  x 2                             1.5 x 2

                            2                                   3

hence Fe₂O₃

molecular formula = (Fe₂O₃)n = 119.55

                     molecular formula = Fe₂O₃

In general, all you need to know is how to calculate the molecular formula from the empirical formula.

This is an easy task to handle and with that overview I hope you are good to handle other questions which may be the same.