What is the empirical formula of C2H4O2?
The empirical formula tells you what the smallest integer ratio between the atoms that make up a substance is.
In essence, the empirical formula can be thought of as the building block of a substance. The molecular formula will thus tell you how many building blocks are needed to form that substance.
So, for a given molecule, the empirical formula will tell you what is the minimum number of atoms of each element needed to form the building block for the molecular formula.
In your case, the molecular formula is given to be
- two atoms of carbon
- four atoms of hydrogen
- two atoms of oxygen
But what is the minimum number of atoms of each element that you need in order to be able to start building the molecule?
The minimum number of atoms an element can contriubte to a building block is
With this in mind, notice that if you divide all these values by
- one atom of carbon
- two atoms of hydrogen
- one atom of oxygen
This tells you that the building block for this particular molecule is
In other words, if you take two such building blocks,