The general molecular formula for alkynes is C_nH_2n-2, where 'n' represents the number of carbon atoms in the alkyne molecule.

Here's why:

* Alkynes are hydrocarbons with at least one carbon-carbon triple bond.

* Each carbon atom forms four bonds. In a triple bond, two carbon atoms share three pairs of electrons.

* The general formula for alkanes is C_nH_2n+2, but alkynes have two fewer hydrogen atoms due to the triple bond.

Examples:

* Ethyne (acetylene): C₂H₂

* Propyne: C₃H₄

* Butyne: C₄H₆