Mechanism of buffers
Mechanism of buffers
Consider a hypothetical weak acid, HA, in a solution with it salt MA. In this solution, HA, will be very slightly dissociated whilst MA is fully dissociated into ions;
HA (aq) ↔ H+(aq) + A–(aq)
MA(aq) → M+(aq) + A–(aq)
Hence the mixture contains a relatively high concentration of un-ionized HA (acid) and relatively high concentration of A– (base)
If an acid is added to this system, the H+ ions in the acid will combine with A—ions to form HA thus removing nearly all the added H+ ions and keeping the pH relatively unchanged.
H+(aq) + A–(aq) → HA(aq)
When an alkali is added to a system, the added
–OH ions combine with the acid to produce water
HA(aq) + –OH(aq) → H2O(l) + A–(aq)
By having the reserves of HA and A- in buffer changes resulting from the addition of acid or alkali are minimized.
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