Determine the ka of an acid whose 0.294 m solution has a ph of 2.80. 1.2 x 10-5 8.5 x 10-6 2.7 4.9 x 10-7 5.4 x 10-3

Question

Jasiah Weber

Chemistry

25 March, 11:34

Determine the ka of an acid whose 0.294 m solution has a ph of 2.80. 1.2 x 10-5 8.5 x 10-6 2.7 4.9 x 10-7 5.4 x 10-3

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Answers (1)

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Jacey Lutz · Answer 1

1) Calculate [H+] from the pH:

pH = log { 1 / [H+] } = - log [H+]

=> [H+] = 10 ^ (-pH)

=> [H+] = 10 ^ (-2.80) = 0.00158

2) Assume the stoichiometry 1:1

=> HA aq - - - > H (+) aq + A (-) aq

=> [A-] = [H+] = 0.00158

[HA] = 0.294 - 0.00158 = 0.29242

3) Calculate Ka

Ka = [H+] * [A-] / [HA] = (0.00158) * (0.00158) / 0.29242 = 8.54 * 10^ - 6

Answer: 8.5 * 10^ - 6