Question

Arsenic acid H3AsO4 is a triprotic acid very similar to phosphoric acid. The acid dissociation constants for the three acidic protons are: Ka1 = 6.46 x 10^-3, Ka2 = 1.15 x 10^-7, and Ka3 = 3.16 x 10^-12. a) What ratio of conjugate base to acid is needed to make an arsenate buffer at pH 6.64? b) Which arsenate species serves as the acid and which serves as the base for the buffer at pH 6.64?

Name: 1 arsenic acid h3aso4 is a triprotic acid very similar to phosphoric acid the acid dissociation constants for the three acidic protons are ka1 646 x 10 3 ka2 115 x 10 7 and ka3 316 x 10 12 a 43981
Uploaded: 2023-01-26T07:01:34-08:00
Duration: 3 min 21 s
Channel: Sri K
Description: 1 arsenic acid h3aso4 is a triprotic acid very similar to phosphoric acid the acid dissociation constants for the three acidic protons are ka1 646 x 10 3 ka2 115 x 10 7 and ka3 316 x 10 12 a 43981

          Arsenic acid H3AsO4 is a triprotic acid very similar to phosphoric acid. The acid dissociation constants for the three acidic protons are: Ka1 = 6.46 x 10^-3, Ka2 = 1.15 x 10^-7, and Ka3 = 3.16 x 10^-12.
a) What ratio of conjugate base to acid is needed to make an arsenate buffer at pH 6.64?
b) Which arsenate species serves as the acid and which serves as the base for the buffer at pH 6.64?

Added by Alexis B.

Chemistry: Structure and Properties

Nivaldo Tro 2nd Edition

Instant Answer

Solved by Expert Sri K

01/26/2023

Step 1

64. Since the pH is closest to the pKa2 (which is the negative logarithm of Ka2), we will use the second dissociation step of arsenic acid, H3AsO4, which involves the equilibrium between H2AsO4^- and HAsO4^2-. Show more…

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Arsenic acid H3AsO4 is a triprotic acid very similar to phosphoric acid. The acid dissociation constants for the three acidic protons are: Ka1 = 6.46 x 10^-3, Ka2 = 1.15 x 10^-7, and Ka3 = 3.16 x 10^-12. a) What ratio of conjugate base to acid is needed to make an arsenate buffer at pH 6.64? b) Which arsenate species serves as the acid and which serves as the base for the buffer at pH 6.64?