Iron(III) chloride is acidic because it is formed by the reaction of a weak base (ferric hydroxide) and a strong acid (hydrochloric acid).that is, Fe(OH)3 + 3HCl →FeCl3 + 3H2O
Sodium carbonate is basic because it is formed from a strong base (sodium hydroxide) and a weak acid (carbonic acid). That is,
2NaOH + H2CO3 → Na2CO3 + 2H2O