Empirical and Moliecular Formula

Today In Class we learnt about two diffrent formulas.  They were very interesting because they are somewhat related.  The two formula we leart are:

Empirical Formula
-It is the simple formulae expressing the compostion of a compound.  It gives the simples whole number ratio of atoms or ions.

eg. The empirical in this case will be Fe3O4 as they are calculated by dividing the number of grams they have
by the total number of mass of the combining compound which is the molar mass.  After Fe and O is divided by the MM than we can use the lowest ratio in this case 1.29 to divide by the other rations like 1.72.  At the end it resulted 3 Fre and 4 Oxygens.  This shows the lowest number formula of the compound.

Molecular Formula
-Is a multiple of the empirical formula.  If the lowest common denominator of the subscripts is 1, the empirical and molecular foulae for the compoud are the same.

eg. Molecular Formula

An organic compound is analyzed and found to be 69.5% carbon, 7.3% hydrogen, and 23.2% oxygen
by mass.  The molar mass of this compound is 276.0g/mol. If the EF is found to be C4H5O than what is its Molecular Formula

Easy!
If we know the the most simple formula of the compound and we were given the molar mass of the original compound which is 276.0g/mol than we can find the MF.

1. We first Find the MM of C4H5O the EF of the compound=69.0g/mol
2. Than we will devid the MM of the EF by the MM of MF which will be 276.0g/mol/69.0g/mol
3. You will than receive the number 4
4. Than you will need to multiply the number 4 to the original EF which will be 4(C4H50)
5. You will than get the MF C16H20O4