1)What is the pH of a buffer prepared by adding 0.405 mol of the weak acid HA to

Question

1)What is the pH of a buffer prepared by adding 0.405 mol of the weak acid HA to 0.608 mol of NaA in 2.00 L of solution? The dissociation constant Ka of HA is 5.66×107. Express the pH numerically to three decimal places. 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. 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.

Explanation / Answer

part A )

moles of HA = 0.405 x 2 = 0.81

moles of NaA = 0.608 x 2 = 1.22

pKa = -log Ka = 6.25

pH =pKa + log [NaA / HA]

pH = 6.25 + log (1.22 / 0.81)

pH = 6.43

part B) 0.150 mol HCl added :

pH = pKa + log [NaA - C / HA + C]

pH = 6.25 + log (1.22 - 0.150 / 0.81 + 0.150)

pH = 6.30

part C) 0.195 mol HCl added :

pH = pKa + log [NaA + C / HA - C]

pH = 6.25 + log (1.22 + 0.195 / 0.81 - 0.195)

pH = 6.61

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.