question on addition reaction :)

[Zahta]

just want to ask a quick question ,  using structural formulae       write the equation  describing the production  of chloroethane  from ethene, why is  hcl a reactant in the equation, where did hcl come from .   thanks

[Mr. Study]

Look at it like this:
       
H\        /H                       Cl\         /H
    C=C             -->           H- C - C - H
H/        \H                          H/       \H

Think about where the H and Chlorine can come from.

If you know combustion, think of combusting Hexane into Carbon Dioxide and Water, What is the other reactact that is needed to produce these products? Oxygen.

Does that help out? :S

From my perspective, It is just thinking about what elements we need to what is, realistically, possible to add. :S