How does Ethylene react with Hydrogen and Bromine.

i) Addition of hydrogen (hydrogenation)
Alkenes react with hydrogen in the presence of pt (or) pd catalyst to form alkanes.
${\mathrm{CH}}_2={\mathrm{CH}}_2+{\mathrm{H}}_2\stackrel{\mathrm{Pt}/\mathrm{pd}}{\to }{\mathrm{CH}}_3-{\mathrm{CH}}_3$
ii) Reaction with Bromine
Ethylene decolourises the red colour of bromine dissolved in CCl₄. This test is used for the detection of unsaturation of organic compound.