Answer
pH of buffer = 10.07
Work Step by Step
(A) Given :
1. [conjugate base] = [H2BO3-] = 0.82 M
2. [acid] = [H3BO3] = 0.12 M
3. pKa of Boric Acid (H3BO3) = 9.24
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(B) Formulae :
1. Henderson - Hasselbalch equation of a buffer :
pH = pKa + log [conjugate base] / [acid]
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(C) Solution :
pH = pKa + log [conjugate base] / [acid]
So,
pH = 9.24 + log (0.82 / 0.12)
= 9.24 + 0.83
= 10.07
Hence, pH of the buffer is 10.07.
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(D) Answer :
pH of buffer = 10.07