When sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) are titrated with an acid, such as hydrochloric acid (HCl), they undergo a series of reactions that involve the release of carbon dioxide gas (CO2). The overall reactions can be represented as follows:

1. Sodium Carbonate (Na2CO3):

Na2CO3 + 2HCl → 2NaCl + H2O + CO2

In this reaction, sodium carbonate reacts with hydrochloric acid to form sodium chloride (NaCl), water (H2O), and carbon dioxide gas. For every mole of sodium carbonate present, one mole of carbon dioxide is released.

2. Sodium Bicarbonate (NaHCO3):

NaHCO3 + HCl → NaCl + H2O + CO2

Sodium bicarbonate reacts with hydrochloric acid in a similar manner, producing sodium chloride, water, and carbon dioxide gas. However, since sodium bicarbonate contains one bicarbonate ion (HCO3-) compared to two carbonate ions (CO32-) in sodium carbonate, only half a mole of carbon dioxide is released for every mole of sodium bicarbonate present.

During the titration, the acid is added gradually to the solution containing sodium carbonate and/or sodium bicarbonate. As the acid is added, it reacts with the carbonate and bicarbonate ions, causing the release of carbon dioxide gas. The endpoint of the titration is reached when all the carbonate and bicarbonate ions have reacted with the acid, and the solution becomes neutral.

Indicators, such as phenolphthalein or methyl orange, are often used to determine the endpoint of the titration. These indicators change color at a specific pH range, signaling the point at which the acid has completely reacted with the carbonate and bicarbonate ions.

Titrations involving sodium carbonate and sodium bicarbonate are commonly used in analytical chemistry to determine the concentration of an unknown acid by measuring the volume of acid required to neutralize a known amount of the carbonate/bicarbonate solution.