Question

pKa of a weak acid (HA) is 4.5. The ratio of
concentration of HA and A^- to have a buffer solution of
pH 5.5 will be
1:100
1:10
1:1
2:5​

Answer 1

Answer:

When [A-]/[HA] remains close to 1, the pH remains close to pKa. As [A-]/[HA] goes from 1/10 to 10 the pH changes from pKa+1 to pKa-1. So as long as [A-]/[HA] is between 1/10 and 10, the pH is within 1 unit of pKa. The addition of a strong acid or base to a buffer changes the ratio [A-]/[HA].

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