A dilute solution of sodium carbonate was added to two test tubes - one containing dilute HCl (A) and the other containing dilute NaOH (B). The correct observation was
A colourless gas liberated in test tube A.
CO2 is a colourless and odourless gas.
Na2CO3 is a basic salt and hence, it reacts with HCl (strong acid) to form NaCl, whereas it undergoes no reaction when it reacts with a strong base like NaOH.