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3.1.16 buffer solutions (HL)

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chem whatarethemechanismsofchemicalchange

Reactivity 3.1.16 - a buffer solution is one that resists change in pH on the addition of small amounts of acid or alkali

a buffer solution is resistant to changes in on the addition of small amounts of acid or alkali

  • water is very vulnerable to significant fluctuations in
  • biological systems are able to operate efficiently only within a narrow range of because of the effect that change has on enzyme action (blood)
  • these systems are dependent on buffers

the ocean can absorb massive amounts of , but it affects lots of ocean creatures by a lot.

as increasing amounts of dissolves into the ocean, it becomes carbonic acid, which dissociates into hydronium and hydrogencarbonate ions.

as the concentration of hydronium ions increases, the equilibrium shifts to the right, decreasing the concentration of carbonate ions which are needed for ocean animals

how buffer solutions work

  • acidic buffers maintain below 7

  • basic buffers maintain above 7

  • mixture of two solutions, should be equal parts same amount of the weak substance and the salt with conjugate

    • eg 1 mol and 1 mol

  • each contain two species of a conjugate acid-base pair

    • acidic buffer has a weak acid and a salt of a strong base
    • basic buffer has a weak base and a salt of a strong acid

  • buffers can only be composed of weak acids and bases as strong acids and bases ionise completely, do not exist in equilibria in solution, and cannot carry out reversible reactions

acidic buffers
composition
  • mixing aqueous solution of a weak acid with a solution of its salt of a strong alkali. for example:

these equilibria exist in this aqueous mixture:

(sodium ethanoate is a soluble salt, so it fully dissociates)

response to added acid and base

added acid :

added base :

this removes most of the

as the added and are used in these reactions, they do not persist in the solution and the is largely unchanged

basic buffers
composition

made by mixing an aqueous solution of a weak base with its salt of a strong acid for example:

these equilibria exist in this mixture of solutions:

the mixture contains relatively high concentrations of both and

response to added acid or alkali

added :

added base ():

the removal of added and by reactions with the components of the buffer solution means that they do not persist in the solution and do not alter the