Iron chloride is acidic because it is formed by the reaction of a weak base and a strong acid HCl.
Sodium Carbonate solution is made by the reaction of Carbonic acid with NaOH.
Therefore, it is alkaline.
It is because, salts of strong acid and weak base will give an acidic solution us, while the salts of weak acid and srtong base, is fine to give us an alkaline solution, for which Sodium carbonate and Iron chloride is an example, and therefore,
Iron chloride is acidic, while Sodium carbonate is basic.
Hope this will help you.