A solute may be dissolved in a solvent because it ionizes in solution or because it dissociates in solution. For instance, when iron metal is dissolved in acid, it is oxidized to FeIII. The chemical identity of the solute has been changed. Similarly, many substances dissociate in solution hence changing the original chemical identity of the solute.
When the electron distribution on the molecule become uneven like one molecule have more electron compare to other.Resonance occurs due to overlap of the orbitals.When electron flow through pi system then resonance occurs.
