Mechanism: The formation of ethylene and diethyl ether from ethanol and conc. H2SO4 may be explained as follows:(a) Formation of ethene or ethylene:Step 1. Due to the presence of two lone pairs of electrons on oxygen, alcohols act as weak bases. Therefore, they react with strong mineral acids (HCl, H2SO4 etc.) to form oxonium salts.Step 2. The presence of a positive charge on the highly electronegative oxygen atom weakens the C—O bond. Thus, the protonated ethanol readily eliminates a molecule of H2O to form ethyl carbocation.This step is slow and hence is the rate-determining step of the reaction.Step 3. The ethyl carbocation formed in step 2 being a reactive chemical species, readily loses a proton to form the ethene molecule.