化學 alkane and alkene 問題

Question

Medicinal paraffin contains alkanes. The gaseous product from cracking contains a mixture of alkanes and alkenes. What test(s) can be used to distinguish alkenes from alkanes?

Answer 1

Test 1 :
Shake the unknown with bromine solution. Alkenes can decolorize the brown bromine solution, but alkanes cannot.

Test 2 :
Shake the unknown with acidified potassium permanganate solution. Alkenes can decolorize the purple permanganate solution, but alkanes cannot.

Answer 2

I think Test 1 has some problem.
Test 1 should be done in the absence of light.
(Both alkane and alkene can decolorize Br2 under light)

Answer 3

by adding Cl2 or Br2
only can react with alkanes