It is a neutralization reaction , When the acetic acid is mixed bicarbonate solution, the ions H3O⁺ acid neutralize OH⁻ ions (-) bicarbonate equilibrium, shifting the equilibrium to the right bicarbonate in order to H₂CO₃ formation. This acid after formed, decomposes, releasing CO₂ .Therefore, the reaction acetic acid and sodium bicarbonate, there is the effervescence of the solution due to the release of CO2 .