Buffers

• A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added.
• Buffers work by having both an acidic component (HA) and its conjugate base (A-).
• Buffers are composed of a weak acid and its conjugate base, or a weak base and its conjugate acid.
• Increasing [H+] shifts the equilibrium to the left, while decreasing [H+] shifts it to the right.
• The equilibrium between HA and A- depends on the pKa value, which is determined by the strength of the acid.
• Strong acids have low pKa values, while weak acids have high pKa values.
• When a strong acid is added to a buffer, it reacts with the conjugate base to form more HA, shifting the equilibrium towards the right.
• Acid dissociation constant (pKa): The equilibrium constant for the ionization reaction of a weak acid.
• Strong acids have low K values and do not form buffers because they completely dissociate into H+ and their conjugate bases.
• When adding HCl to a buffer, the concentration of H3O+ increases, causing the equilibrium to shift towards the formation of more HA molecules.
• When adding strong acid to a weak acid/conjugate base system, the concentration of H+ increases, causing the equilibrium to shift towards the formation of more HA molecules.
• Adding NaOH to a buffer causes the concentration of OH- to increase, shifting the equilibrium towards the formation of more A-. This reduces the amount of free hydrogen ions present in the solution.
• Acidic buffers contain a weak acid as their main component, with the addition of a strong base such as sodium chloride (NaCl) to maintain electrical neutrality.
• This reaction consumes H+ ions from the solution, reducing their concentration and increasing the pH.
• Adding a strong base to a buffer will react with the acid to produce more A-, shifting the equilibrium towards the left.
• Conjugate acid/base pair: Two species that differ only by one proton.