What happens when:

(i) Ethyl alcohol is heated in the presence of Al₂O₃ at 493 K? 

(ii) Ethylene dibromide is heated with zinc dust?

Explain the mechanism of the following reaction:

How are alkenes prepared from Alkynes ?

The -bond is weaker than carbon-carbon σ bond. Explain.

Why are alkenes more reactive than alkanes ?

Why do alkenes undergo electrophilic addition reactions?

Discuss the mechanism of addition of bromine to ethylene.

Discuss the mechanism of addition hydrogen acids to symmetrical alkenes. Justify the order of reactivity of halogen acids HI > HBr > HCl.

Define Markownikoff's rule giving an example.