The dissociation of the weak acid ‘HA’ would be shown as:HA (aq) ⇌ H+ (aq) + A– (aq)Adding alkali will add OH- ions to the solution. These will react with the H+ ions present in the solution, producing water (H2O). As a result, the concentration of H+ ions will decrease. The system will react to oppose this change, so the position of equilibrium will move towards the side with the H+. Therefore, the position of equilibrium will move to the right (product side). In order to replace the lost H+ ions, some HA molecules will dissociate forming A- ions in the process. This means the fall in H+ concentration is resisted and the pH of the buffer solution remains fairly constant.