Question

How can empirical and molecular formulas be the same?

Answer 1

In order to answer this question, we have to explain the situation in which the empirical formula is the same as the molecular formula. And then we will also differentiate both the empirical and the molecular formula.

Complete answer:
As we know, the empirical formula is the simplest whole number ratio defining constituent atoms in a species. The molecular formula is some multiple of this empirical formula, and the multiple may be 1.
Or in other words, according to the definition of molecular formula, it is the multiple of empirical formula, and when the multiple of empirical formula is 1 times then the molecular formula is as same as the empirical formula.
A good example of this is ethanol, ${C_2}{H_6}O\;(C{H_3}C{H_2}OH)$ . As there is only one oxygen atom in the molecule, this molecular formula cannot be simplified, so this is also its empirical formula.
An empirical formula is the simplest type of formula used to express the composition of a compound whereas the molecular formula is the exact representation of the actual compound. This is the main difference between empirical and molecular formulas.
Empirical formula is the simplest form of expressing the elemental composition of a compound.
Molecular formula is the actual representation of the elemental composition of the compound.

Note:
It is also worth remembering why we learn about empirical formulae. Percentage composition information will lead to an empirical formula, not necessarily the molecular formula. We use the molar mass to determine the molecular formula from the empirical formula.