Is CO2 acid or base?
CO2 gas is a Lewis acid in that it accepts electrons from Lewis bases (electron donors). For example CO2 will react with alkyl anions to give the salts of organic acids. When dissolved in water a reaction takes place between the Lewis donor (water) and the CO2 which gives rise to carbonic acid which is a different substance to CO2 and has the formula (H2CO3). The reaction is in equilibrium with the atmosphere above and when the said atmosphere is deficient in CO2 the reverse occurs and CO2 is liberated and example of Le Chatelier principal.
