How does a buffer solution work when we add acid to a buffer solution like butanoic acid and sodium butonoate

Question

jfraser · Answer

buffers are made of a weak acid (or base) and its conjugate. These 2 ions establish an equilibrium between the dissociation of the acid and the reassociation of the conjugate$$HA(aq) \rightleftharpoons H^{+1}(aq) + A^{-1}(aq)$$ If you didn't have any of the conjugate, the concentration of A- will be very low, and the concentration of HA will be fairly high. In a buffer, you've got almost equal concentrations of both ions
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When you add a small amount of acid or base, it doesn't change the ratio of A- to HA in the buffer by a noticeable amount, so the pH doesn't change appreciatively