Reaction rates. Reaction rate increases with concentration of reactants. This effect is demonstrated here using the reaction of chalk (calcium carbonate, CaCO3) with hydrochloric acid (HCl) and acetic acid (CH3COOH), both 0.5 M molar concentration. Hydrochloric acid is a strong acid and completely dissociates in an aqueous solution. Acetic acid is a weak acid and only partially dissociates. Therefore, for the same molar concentration, hydrochloric acid produces a higher concentration of hydronium ions (H3O+) that drive the reactions. Carbon dioxide (CO2) bubbles are produced in the respective reactions: CaCO3 + HCl -> CaCl2 + H2O + CO2 and CaCO3 + CH3COOH -> (CH3COO)2Ca + H2O + CO2. The reaction is visibly more vigorous (higher reaction rate) in the left beaker (hydrochloric acid) than in the right beaker (acetic acid).