Explain the addition of sulphuric acid to alkenes with the help of a reaction.

(N/A) The addition of concentrated sulphuric acid to alkenes follows the electrophilic addition mechanism.
$(i)$ For ethene:
$CH_2=CH_2 + H-OSO_3H \xrightarrow{298 \ K} CH_3-CH_2-OSO_3H$ (Ethyl hydrogen sulphate)
$(ii)$ For propene:
$CH_3-CH=CH_2 + H-OSO_3H \xrightarrow{298 \ K} CH_3-CH(OSO_3H)-CH_3$ (Isopropyl hydrogen sulphate)
Mechanism:
$1$. The sulphuric acid dissociates to provide an electrophile $H^{\delta+}$ and a nucleophile $^{-}OSO_3H$.
$2$. The electrophile $H^{\delta+}$ attacks the $\pi$-bond to form a carbocation.
$3$. In the case of unsymmetrical alkenes like propene,the reaction follows Markovnikov's rule,where the more stable carbocation $(CH_3-CH^+-CH_3)$ is formed.
$4$. The nucleophile $^{-}OSO_3H$ then attacks the carbocation to form the final alkyl hydrogen sulphate product.