Buffer solutions have constant acidity and alkalinity because
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these give unionised acid or base on reaction with added acid or alkali
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acids and alkalies in these solutions are shielded from attack by other ions.
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they have a large excess of H+ or OH- ions
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they have fixed value of pH
A.
these give unionised acid or base on reaction with added acid or alkali
If a small amount of an acid or alkali is added to a buffer solution, it converts them into unionised acid or base. Thus, remains unaffected or in other words its acidity/alkalinity remains constant. e.g.,
H3O+ + A- ⇌ H2O +HA
-OH +HA → H2O +A-
If acid is added, it reacts with A- to form undissociated HA. Similarly, if base/alkali is added, O H- combines with HA to give H2O and A- and thus, maintains the acidity/alkalinity of buffer solution.
