Na2Co3 also gives a salt, CO2 and water. Or you can reduced it using LIAlH4 or NaBH4 giving a primiary alcohol. Or using PCl5 gives acid chloride + POCl3 and HCl gas (steamy white fumes) Carboxylic acid + alcohol gives ester + water Caboxylic acid + NaOH gives salt and water
as far as i know, to test for a carboxylc acid is to use Na2Co3 which gives of CO2-this the basic test for an acid so in order to prove there is an OH grop, use PCl5-which gives of HCl-white steamy fumes-when tested with the top of a conc. NH3 bottle gives dense white clouds!