The general formula `C_(n)H_(2n-2)` is of the alkyne series . We know that the first member of the alkyne series is ethyne `(C_(2)H_(2))` and it has 2 carbon atoms in its molecule.

(i) Since the first member of alkyne series has 2 carbon atopmes in the therefore, third member of alyne series will have 4 carbn atoms in its molecule . Soif wer put n=4 in the general formula `C_(n)H_(2n-2)` then the molecular formula of the fifth memeber of the alkyne series will be `c_(6)H_(2)xx6-2 "or" C_(6)H_(10)`.