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3. Suppose you need to prepare a buffer for a pH of 10.6. An acid-base pair (HA/A) to use has the pKa value of 9.8. Describe

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Answer #1

pH of buffer solution to be prepared = 10.6

pKa = 9.8

a) Calculation of ratio of [A-]/[HA]

According to Henderson Hasselbalch equation

pH = pKa + log10[A-]/[HA]

10.6 = 9.8 + log10[A-]/[HA]

0.8 = log10[A-]/[HA]

[A-]/[HA] = 6.31

b) As this is acidic buffer we have to have mixture of weak acid (HA) and its conjugate base (A- ) which is strong base hence we have to add strong base.

c) we know that [A-]/[HA] = 6.31/1 hence for 1 equivalent of HA we require 6.31 equivalent of A- hence it is clear that we need to add 6.31 equivalents of strong base.

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