Explain the dehalogenation of vicinal dihalides with an example.

Vicinal dihalides are compounds in which two halogen atoms are attached to two adjacent carbon atoms.
Dehalogenation: When vicinal dihalides are treated with zinc metal,they lose a molecule of $ZnX_2$ to form an alkene. This reaction is known as dehalogenation.
Examples:
$(i)$ $CH_2Br-CH_2Br + Zn \xrightarrow{\Delta, \text{Ethanol}} CH_2=CH_2 + ZnBr_2$
($1,2$-Dibromoethane gives Ethene)
(ii) $CH_3-CHBr-CH_2Br + Zn \xrightarrow{\Delta, \text{Ethanol}} CH_3CH=CH_2 + ZnBr_2$
($1,2$-Dibromopropane gives Propene)