HELP WITH PART B PLEASE the answer is not 8.79 A certain weak acid, HA, with a K
ID: 1050868 • Letter: H
Question
HELP WITH PART B PLEASE the answer is not 8.79
A certain weak acid, HA, with a Ka value of 5.61×106, is titrated with NaOH.
Part A
A solution is made by titrating 9.00 mmol (millimoles) of HA and 2.00 mmol of the strong base. What is the resulting pH?
Express the pH numerically to two decimal places.
4.71
Part B
More strong base is added until the equivalence point is reached. What is the pH of this solution at the equivalence point if the total volume is 43.0 mL ?
Express the pH numerically to two decimal places.
_____
pH =4.71
Explanation / Answer
B) at equivalence point total acid becomes salt
[NaH] = 9 / 40 = 0.225 M
pH = 1/2 [ pKw + pKa + log C]
pKa = - log Ka = - log [5.61 x 10-6] = 5.25
pH = 1/2 [ 14 + 5.25 + log 0.224]
pH =1/2 [18.6]
pH = 9.3
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