Which condition would convert a Haloalkane to an Alkene?

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Elimination of HX from a haloalkane to form an alkene happens when a strong base abstracts a β-hydrogen and the leaving group departs, creating a carbon–carbon double bond (an E2 process). Using a strong base in an alcoholic solvent, like KOH in alcohol, provides the right combination: a powerful base in a medium that favors elimination over substitution, and heating supplies the energy needed for the E2 step. This setup efficiently pulls off the β-hydrogen while the halide leaves, giving the alkene.

The other conditions don’t promote this pathway as reliably. Aqueous acid (water with H+) tends to favor substitution/hydrolysis to alcohol rather than elimination. Ammonia as a solvent/base is a weaker, less effective medium for E2. Concentrated sulfuric acid can promote dehydration in other contexts, but it’s not the standard, straightforward route to an alkene from a haloalkane as alcohol-based base elimination is.