6.7 MOLECULAR AND STRUCTURAL FORMULA

A structural formula of a compound shows the arrangement of atoms present in it. Whereas a molecular formula shows the number of atoms of each element. For example,

Structural formula of n-Butane is CH3-CH2-CH2-CH3 and its molecular formula is C4H10

How can you write the molecular formula of a compound from its structural formula?

Follow the following steps:

  1. Identify different types of elements present in the structural formula.
  2. Write symbols of these elements side by side in a line.
  3. Count the number of atoms of each element from the structural formula.
  4. Show this number of atoms as subscripts of symbol of corrosponding element.

Example 6.13: Writing the molecular formula of the following compound.

CH3-CH2-CH2-OH

Solution: C3H8O

CONCEPT ASSESSMENT EXERCISE 6.8

Write the molecular formulae of the following compounds:

  1. CH3-CH2-OH
  2. CH3-CH2-NH2
  3. CH3-CO-CH3