A total of 100 ml of 2.1 M weak acid is mixed with 300 ml of...

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Answer 1

Answer #1

millimoles of weak acid = 100 x 2.1 = 210

millimoles of base added = 300 x 0.1 = 30

210 - 30 = 180 millimoles acid left

[acid] = 180 / 400 = 0.45 M

[salt] = 30 / 400 = 0.075 M

pH = pKa + log [salt] /[acid]

4.13 = pKa + log 0.075 / 0.45

4.13 = pKa -0.78

pKa = 4.91

Ka = 10^-pKa = 10^-4.91

Ka = 1.23 x 10^-5

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Answer 2

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