The reaction between acetic acid CH3COOH and sodium acetate CH3COONa can be represented as follows:CH3COOH + OH- CH3COO- + H2OThis is a typical acid-base reaction, where acetic acid donates a proton H+ to the hydroxide ion OH- . The equilibrium constant for this reaction is given by the expression:K = [CH3COO-][H2O] / [CH3COOH][OH-]When the pH of the solution is increased from 3 to 5, the concentration of H+ ions decreases, and the concentration of OH- ions increases. According to Le Chatelier's principle, the equilibrium will shift to counteract this change. In this case, the equilibrium will shift to the right, favoring the formation of CH3COO- acetate ion and H2O.As a result, the concentration of acetic acid CH3COOH will decrease, and the concentration of sodium acetate CH3COONa will increase. This shift in equilibrium will help to buffer the solution, maintaining a relatively constant pH in the presence of small amounts of added acid or base. This is the basis for the buffering action of the acetic acid-sodium acetate system.