What is CO3 + NaOH ----> ? + H2O

so... CO3 has acidic properties as oxides of a non metal is an acid. So then it should react with the sodium hydroxide so give a salt and water???

No such stuff as CO3.
Did you mean CO2?
then:
CO2 + 2NaOH ---> Na2CO3 + H2O
acidic........alkali.................s…
gas

Carbon trioxide (CO3) is an unstable oxide of carbon (an oxocarbon)
2 CO3(g) + 4 NaOH(aq) ---------> 2 Na2CO3(aq) 2 H2O(l) + O2(g)