Question

A compound has a molar mass of 90 grams per mole and the empirical formula CH2O. What is the molecular formula of this compound?

Answer 1

CH2O = 12 + 2 + 16 = 30
90 /30 = 3
3 x (CH2O) = C3H6O3

Answer 2

Answer : The molecular formula of the compound will be, $C_3H_6O_3$

Explanation :

Empirical formula : It is the simplest form of the chemical formula which depicts the whole number of atoms of each element present in the compound.  

Molecular formula : it is the chemical formula which depicts the actual number of atoms of each element present in the compound.  

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is :

$n=\frac{\text{molecular mass}}{\text{empirical mass}}$

As we are given that the empirical formula of a compound is $CH_2O$ and the molar mass of compound is, 90 gram/mol.

The empirical mass of $CH_2O$ = 1(12) + 2(1) + 1(16) = 30 g/eq

$n=\frac{\text{molecular mass}}{\text{empirical mass}}$

$n=\frac{90}{30}=3$

Molecular formula = $(CH_2O)_n=(CH_2O)_3=C_3H_6O_3$

Thus, the molecular formula of the compound will be, $C_3H_6O_3$