Question

How do you convert empirical formula to molecular formula?

Answer 1

Hint:‌Empirical formula is defined as the simple whole number ratio of various atoms in the compound. Molecular formula is defined as the number of atoms present that combine together to give a compound.


Complete step by step answer:
The molecular formula of the compound is equal to the $n$ multiple of empirical formula.
To convert an empirical formula into molecular formula-
$E=\dfrac{M}{n}$
Where, $M$ is the molecular formula
$E$ is the empirical formula
To calculate empirical formula, these steps need to be followed:
By using molar mass, convert the mass of the element into moles.
After that, we divide each value of mole by the smallest number of moles calculated.
Then, this value is rounded off to the nearest whole number.
This value is the mole ratio of the elements, that can be represented by subscripts in the empirical formula.
Now let us take an example to convert a empirical formula $N{{O}_{2}}$ into molecular formula, given the molar mass of this molecule is $92gmo{{l}^{-1}}$ .
First, we will calculate the empirical mass of $N{{O}_{2}}$
$14+2(16)$
$\Rightarrow 46gmo{{l}^{-1}}$
Now, we will find the value of $n$ by the equation.
$n=\dfrac{molecular\,mass}{empirical\,mass}$
Now, substituting the values we get,
$n=\dfrac{92}{46}$
On further solving, we get
$n=2$
Now that we have calculated the value of $n$ , we will find the molecular formula
$M=n\times E$
Now, substituting the value of $n$ , we get
$M=2\times (N{{O}_{2}})$
$M={{N}_{2}}{{O}_{4}}$
Therefore, the molecular formula will be equal to ${{N}_{2}}{{O}_{4}}$.

Note:When there is no data available, we use empirical formula for primary analysis.Empirical formula is a theoretical approach that helps us in data analysis and helps in the production prediction of the compound.The molecular formula shows the number of types of atoms in a molecule.