Hydrocarbons

Acid catalysed hydration of alkenes involves formation of carbocation intermediate. Higher the stability of carbocation intermediate, more is the reactivity towards acid catalysed hydration. The order of stability of carbocations (formed) is

Thus, the order of reactivity towards acid catalysed hydration is

The calorific value of dihydrogen is maximum hence it releases maximum energy on combustion.

During Friedel-craft alkylation of benzene with - propyl bromide, the product will be isopropyl benzene (cumene) not -propyl benzene because isopropyllum ion is more stable (as it is carbocation) than -propylium ion ( carbocation).

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Thus

Here and are asymmetrical, due to which it is a chiral molecule.

(Addition of hydrogen halide to give alkene takes place in accordance with Markownikoffs rule).

According to Huckel?s rule for aromaticity, planar monocyclic rings containing electrons (where and so on) should be aromatic. Another requirement for aromaticity is planarity of the ring. In the given compounds, all contains electrons, therefore for them, comes out be ,hence, pyrrole, thiophene and furan are all aromatic.