Question

The empirical formula of a compound is ${\mathrm{CH}}_2\mathrm{O}$. Find the molecular formula of the compound if its molecular weight is $180$.

Answer 1

Step 1. Empirical formula and molecular formula

• An empirical formula represents the simplest whole-number ratio of various atoms present in a compound.
• The molecular formula shows the exact number of different types of atoms present in a molecule of a compound.

Step 2. Formula to determine the value of $n$

$n=\frac{\text{Molecular mass}}{\text{Empirical formula mass}}$

Step 3. Calculation of Empirical formula mass

The empirical formula mass of ${\mathrm{CH}}_2\mathrm{O}$

$[12+(2\times 1)+16]\text{g}=30\text{g}$

Step 4. Calculate the value of $n$

$n=\frac{180\text{g}}{30\text{g}}=6$

Step 5. Formula for the calculation of molecular formula

$\text{Molecular formula=}{\left[\text{Empirical formula}\right]}_n$

Step 6. Calculation of molecular formula

$\text{Molecular formula=}{\left[{\text{CH}}_2\text{O}\right]}_6{\text{=C}}_6{\text{H}}_{12}{\text{O}}_6$

Hence, the molecular formula of the compound is ${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}$.