How to find Empirical Formula from a Molecular Formula
The empirical formula is the simplest whole numbers non-reducible ratio formula for a molecular formula or compound. The empirical formula of the molecular formula C4H6 is C2H3 (divided by 2) because it can't be divided by other numbers than 2 and still only contain integers.
Example - How to find Empirical Formula From Element Mass
We can determine the empirical formula (simplest formula) by using mass of each element in the compound data. A compound is composed of 5.045g of carbon, 0.847g of hydrogen, and 3.36g of oxygen. Find the empirical formula for this compound knowing that H = 1 g/mole , O = 16 g/mole and C = 12 g/mole
First, convert the grams of each element to moles:
5.045/12 = 0.42 mole C , 0.847/1 = 0.847 mole H , 3.36/16 = 0.21 mole O
Divide each of the three mole figures by the lowest of the three in order to simplify the mole ratio.
0.21/0.21 = 1 mole O , 0.42/0.21 = 2 mole C , 0.847/0.21 = 4 mole H
Well, that's 1 O , 2 C and 4 H
The resulting SIMPLEST WHOLE NUMBER empirical formula : C2H4O
NOTE: In this case all mole figures represent whole numbers, so we can say that this is the SIMPLEST WHOLE NUMBER formula. If one of the numbers was (say) 1.5, we have to multiply all the mole figures by 2.
Finding the Empirical Formula using CHEMIX School
A compound is composed of 5.045g of carbon, 0.847g of hydrogen, and 3.36g of oxygen. Find the empirical formula
Step 1) Determine moles: Insert 5.045gC (0.42 moles) , 0.847gH (0.84 moles) , 3.36gO (0,21 moles)
Step 2) Divide all moles figures by 0.21: 0.42/0.21 = 2C 0.84/0.21 = 4H 0.21/0.21 = 1O
The resulting SIMPLEST WHOLE NUMBER empirical formula : C2H4O