Final answer:
The reaction of chlorine with a compound in the presence of light likely refers to a halogenation reaction, where chlorine adds to or substitutes atoms in an organic compound, such as ethylene, to form ethylene dichloride.
Step-by-step explanation:
The student's question pertains to the reaction of a compound with chlorine in the presence of light. When chlorine is exposed to light, it can undergo photochemical reactions. For example, when chlorine reacts with hydrocarbons, it can add to multiple bonds or substitute hydrogen atoms in a process known as halogenation.
In the case of the reaction of chlorine with an alkene such as ethylene, the reaction produces ethylene dichloride. This reaction typically occurs under mild conditions and does not require a catalyst; it involves the addition of a chlorine molecule across the double bond of the alkene.
To summarize the process, in the presence of light, the chlorine molecule can react with ethylene to form ethylene dichloride through a halogen addition reaction:
Cl2 (g) + C2H4 (g) → C2H4Cl2 (l)