Question

What is the difference between two consecutive members in a homologous series in alkanes in terms of: (i) Molecular mass, (ii) Number of atoms of elements.

Answer 1

(i) Molecular mass :
In term of molecular mass each successive member in a homologous series differ by molecular mass of 14 Dalton by the preceding member.
(ii) Number of atoms :
There is a difference of one carbon atom and two hydrogen atom between two consecutive members of homologous series that is of one CH2 molecule or three atoms.

Answer 2

Difference between two consecutive members in a homologous series in alkanes in terms of: (i) Molecular mass - 14 grams/mole (ii) Number of atoms of elements - 3

• The homologous series is the sequential arrangement of compounds which have same functional group. Each member has increasing number of carbon atoms and hence hydrogen atoms to fulfill their valency.
• So, for alkane, each consecutive compound has increased -CH2 group.
• -CH2 group weighs 14 gram/mole and it has three atoms namely 1 carbon and 2 hydrogen atom.