How are diazonium salts prepared ?

Explanation

Diazotisation : The conversion of aniline or other aromatic primary amines into diazonium salts by the action of nitrous acid and dilute hydrochloric acid is called diazotisation. Nitrous acid needed for the reaction is prepared in situ by the action of dil. HCI on sodium nitrite. As both nitrous acid and the diazonium salt produced are unstable at a higher temperature, dizotisation is always carried out in ice cold solution.
`NaNO_(2)+HCloverset(273-278K)rarrNaCl+HNO_(2)`
`underset("Aniline")(C_(2)H_(5)NH_(2))+HNO_(2)+HCloverset(273-278K)rarrunderset("Benzenediazonium chloride")(C_(6)H_(5)-overset(+)N=NCl^(-)+2H_(2)O)+2H_(2)O`