Carbon dioxide + Sodium hydroxide

Carbon dioxide reacts with sodium hydroxide to give sodium carbonate.
CO2 + 2NaOH → Na2CO3 + H2O

In the presence of water, excess carbon dioxide would react with sodium carbonate to give sodium hydrogencarbonate.
Na2CO3 + H2O + CO2 → 2NaHCO3
The amount of CO2 in air is insufficient to give NaHCO3 with sodium hydroxide.

At room condition, sodium hydrogencarbonate (NaHCO3) is a white solid, which can dissolve in water to give a colourless solution.