[rolnor]

Its not really essy to be 100% sure how fast the alkene would react:
https://en.wikipedia.org/wiki/Hydrohalogenation

[OrganicH2O]

just out of curiosity Rolnor, did you have a specific example in mind? I see two examples from that wikipedia page where addition of HX would be especially fast: one that might proceed through a secondary benzylic carbocation (which is more stable than a tertiary carbocation), and an example of conjugate addition of HX, both good examples of especially reactive alkenes. But for both of those examples, it seems fairly easy to predict that the alkenes would react especially quickly.

[rolnor]

No, I just find it hard to completely exclude that some HCl will add.

[xshadow]

Thanks!!

So in that excercise  If I suppose that also some C=C will react (explaining this) I think is not an error