Question

Write the name and formula of the 3rd member of homologous series having general formula CnH2n-2​

Answer 1

CnH2n-2​ is the formula for Alkyne.

The Third member of the homologus series is Propyne.

Explanation: CnH2n-2

= C3 H2x3-2 (we keep 3 because it is the 3rd member of series)

= C3H4

Since this is an Alkyne therefore we can add suffix to prop(3rd member) and then it becomes Propyne.

Answer 2

Given,

general formula = $C_{n} H_{2n-2}$

This is the general formula for alkyne.

n= 3

To Find,

3rd member of homologous series of alkyne

Solution,

putting the value of n in the above formula, we get,

$C_{3} H_{(2 X3)-2}$= $C_{3} H_{4}$

∴Since it's the third member of the alkyne family, its name is propyne with formula $C_{3} H_{4}$