Part A What is the pH of a buffer prepared by adding 0.708 mol of the weak acid

Question

Part A What is the pH of a buffer prepared by adding 0.708 mol of the weak acid HA to 0.507 mol of NaA in 2.00 L of solution? The dissociation constant K, of HA is 5.66 x 10- Express the pH numerically to three decimal places Hints pH- Submit My Answers Give Up Part B What is the pH after 0.150 mol of HCl is added to the buffer from Part A? Assume no volume change on the addition of the acid Express the pH numerically to three decimal places Hints pH- Submit My Answers Give Up Part C What is the pH after 0.195 mol of NaOH is added to the buffer from Part A? Assume no volume change on the addition of the base. Express the pH numerically to three decimal places Hints pH- Submit My Answers Give Up Provide Feedback Continue

Explanation / Answer

A)

this is a buffer, since there is HA and A-

pH = pKa + log(A-/HA)

pH = -log(5.66*10^-7) + log(0.507/0.708)

pH = 6.10

B)

after adding H+

mol of HA = 0.708+0.15

mol of A- = 0.507-0.15

pH = -log(5.66*10^-7) + log((0.507-0.15)/(0.708+0.15))

pH = 5.866

C)

after adding OH-

mol of HA = 0.708-0.195

mol of A- = 0.507+0.195

pH = -log(5.66*10^-7) + log((0.507+0.195)/(0.708-0.195))

pH = 6.383

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