Chemistry
Mikewillruhl
2015-11-03 20:27:27
A 0.2 m solution of a weak acid ha dissociates such that 99.4% of the weak acid remains intact (i.e., remains as ha). what is the pka of the weak acid?
ANSWERS
syko
2015-11-04 00:33:18

HA -----> H(+) + A(-) 0,2-x.........x..........x 100% - 99,4% = 0,6% = 0,006 x = 0,6%×0,2 = 0,006 × 0,2 = 0,0012 HA --------------> H(+) + A(-) 0,2-x.....................x..........x 0,2-0,0012.....0,0012..0,0012 0,1988.............0,0012..0,0012 K = [H+][A-]/[HA] K = (0,0012)^2/0,1988 K = 0,0000072434 pKa = -logK= -log0,0000072434 = 5,14 :)

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