[Jekel0000]

The problem is for a General Chemistry Student to find the Empirical or Chemical Formula for the Unknown Substance. The difficulty is that there was no mentioning of the Molecular weight of the Unknown Substance....below is the question...and below the question is a question just like it accept I gave the answer....

[Borek]

If I understand correctly what you wrote, neither question asks for a chemical formula, just for empirical formulas. If so, you don't need molar mass.

[magician4]

if you already (correctly) calculated that the molar ratio Fe : C in your substance is to be  1 : 5 , and if you knew that the general formula of your compound is to be written Fe_x(CO)_y , what's your problem remaining?


regards

Ingo

[Jekel0000]

what is left is to find the empirical formula of the unknown reactant

[Hunter2]

Nothing.  You have 1 Fe   to 5 CO . So what is the formula now?

[Jekel0000]

Look according to stoichiometric the sum of the product in an ideal reaction are equal to the sum of the reactence, therefore the molar mass of the unknown substance should be Σproduct(in grams) - O₂(in grams) unfortunately I don't know how much O₂ in grams but I can figure out the number of mols per reactant and then find a Ratio, but I still need a molar mass in order to find the Chemical/Empirical Formula of the Unknown Fe O compound....

[Borek]

therefore the molar mass of the unknown substance should be Σproduct(in grams) - O₂(in grams)

That's incorrect. Mass of product minus mass of oxygen givens mass of the original reactant.

unfortunately I don't know how much O₂ in grams

You can easily calculate it. All you need is the thing mentioned above, in the first half of my post. You know mass of the original substance and you are given masses of the products. Knowing these things you can easily calculate how much oxygen was used.

[mjc123]

You seem to be unclear about the definitions of the different types of formula. The empirical formula is the molar ratio, expressed in its lowest terms, of the elements present in the compound. To calculate this you do not need to know the molecular weight, and from it you cannot calculate the molecular weight of the compound.
The molecular formula gives the actual number of atoms of each element in a molecule of the compound; from it you can calculate the molecular weight. If you know the empirical formula and the molecular weight, the molecular formula can be found by multiplying the empirical formula by the ratio (molecuar weight/empirical formula weight).
You have done this for styrene, but get the terminology wrong; the empirical formula is CH and the molecular formula is C₈H₈.
Both questions ask for the empirical formula and give you enough data to calculate it. Neither asks for the molecular formula, so the molecular weight is not needed.