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From p K a to the pH of weak base solutions
Author(s) -
McEvoy James P.
Publication year - 2020
Publication title -
biochemistry and molecular biology education
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 39
eISSN - 1539-3429
pISSN - 1470-8175
DOI - 10.1002/bmb.21336
Subject(s) - conjugate , base (topology) , conjugate acid , weak base , dissociation constant , acid–base reaction , chemistry , dissociation (chemistry) , acid dissociation constant , strong acids , analytical chemistry (journal) , mathematics , chromatography , inorganic chemistry , aqueous solution , ion , mathematical analysis , biochemistry , organic chemistry , receptor
Undergraduate biochemistry students frequently find the quantitative treatment of weak acids and bases troublesome. Given the p K a of a weak acid HA , for instance, many students struggle to calculate the pH of a solution of the conjugate base A − at concentration C , pH(A − , C ) . The traditional method involves calculating the base dissociation constant K b and the artificial quantity pOH before reaching pH, but these steps increase the risk of mistakes and provide little insight into acid–base equilibria. The alternative method presented here allows students to calculate the pH of a weak base solution from the p K a of its conjugate acid without calculating K b and pOH, using a memorable relationship: pH(HA, C ) + pH(A − , C ) = p K a + 7.