HCl is a strong acid therefore complete ionisation takes place HCl ---> H⁺ + Cl⁻ 1 mol of HCl dissociates to form 1 mol of H⁺ NaOH is a strong base therefore complete ionisation takes place NaOH ---> Na⁺ + OH⁻ 1 mol of NaOH dissociates to form 1 mol of OH⁻ ions equal number of moles of HCl and NaOH will dissociate to give out an equal number of moles of H⁺ and OH⁻ ions. H⁺ + OH⁻ --> H₂O equal amount of H⁺ and OH⁻ together forms H₂O since all the H⁺ and OH⁻ have now reacted to form water molecules the solution now becomes neutral as there are no excess H⁺ ions to make the solution acidic and no excess OH⁻ ions to make the solution basic.
