If a molecule has an empirical formula of c2h2o and a molecular mass of 84.0 g/mol, what is the molecular formula?

=C₄H₄O₂

Explanation:

Given the empirical formula of a molecule, the he the quotient of the molecular mas and and the empirical mass=constant.

84.0 g/mol/mass of(C₂H₂O)=constant

=84/(12×2+1×2×16)

=84/42

=2

Therefore, the molecular formula is (C₂H₂O)₂=C₄H₄O₂

is the molecular formula

Explanation:

Empirical formula is the simplest form of a Molecular formula.

For example  

Molecular formula of glucose is

Its empirical formula is

The subscript numbers of the molecular formula is divided by a common number n=6 here.

Another example:

Molecular formula of Octane is and Its empirical formula will be  

Subscripts divided by n=2.

To find n we make use of the formula  

So, we see n=2 here

Empirical formula × n = molecular formula

is the molecular formula

(Answer)

Please note:

Molar mass is the mass of 1 mole of the substance and its unit is g/mol .

n is the number of moles by which the empirical formula is multiplied to get the molecular formula of the compound.