Here's why:

* Chlorination Mechanism: Chlorination of alkanes is a free radical reaction. The chlorine molecule (Cl₂) breaks down into chlorine radicals (Cl•) in the presence of UV light. These radicals then attack the alkane, removing a hydrogen atom and forming an alkyl radical. This alkyl radical then reacts with another chlorine molecule to form the chlorinated alkane and another chlorine radical, continuing the chain reaction.

* Formation of HCl: The hydrogen atom that is removed from the alkane combines with the chlorine radical to form hydrogen chloride (HCl).

Example:

The chlorination of methane (CH₄) produces chloromethane (CH₃Cl) and hydrogen chloride (HCl):

CH₄ + Cl₂ → CH₃Cl + HCl

Let me know if you have any other questions!