So, to get started, lets know what is an organic compound.
-An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon.
The empirical formula of an organic compound can be found by:
-Burning the compound
-Collecting and weighing the products
-From the mass of the products, the moles of each element in the original organic compound can be calculated
Ex. What is the empirical formula of a compound that when a 5.00 g sample is burned produces 15.0 g of CO2 and 8.18 g of H2O?
First let the empirical formula of the compound be CxHy
CxHy + z O2 = x CO2 + y/2 H2O
We want to find x and y (the simplest ration of the atoms or moles of the elements).
From the equation above, we can see that ALL of the C and the H in CxHy went into making x CO2 and y/2 H2O
mol CO2 = 15.0 g CO2 x 1 mol CO2 / 44.0 g CO2 = 0.341 mol
mol H2O =8.18 g H2O x 1 mol H2O / 18.02 g H2O = 0.454 mol
0.454 moles of water and 0.341 moles of Carbon dioxide were produced
mol C = 0.341 mol CO2 x 1 mol C / 1 mol CO2 = 0.341 mol C
mol H = 0.454 mol H2O x 2 mol H / 1 mol H2O = 0.908 mol H
Divide both by the smallest molar amount
Carbon 0.341 / 0.341 = 1
Hydrogen 0.908 / 0.341 = 2.66
Scale ratio to whole numbers
2.66 x 3 = 8 H
0.341 x 3 = 3 C
C3H8
