Question

The molecular formulae of two members of a homologous series are C₃H₄ and C₆H₁₀. Write the molecular formula of the member with five carbon atoms in a molecule.

Answer 1

One can observe that the given compounds belong to the “alkyne” family, where the molecular formula can be generally represented as C_nH_2n-2. Here, ‘n’ denotes the number of carbon atoms. 

For a molecule with 5 carbon atoms, n=5 and hence the molecular formula will be C₅H_2x5-2 or C₅H₈ (pentyne)