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#5) Correct answer is most important, but feel free to show work. Thanks! The ha

ID: 958248 • Letter: #

Question

#5) Correct answer is most important, but feel free to show work. Thanks!

The half-equivalence point of a titration occurs half way to the end point, where half of the analyte has reacted to form its conjugate, and the other half still remains unreacted. If 0.540 moles of a monoprotic weak acid (K_a = 1.0 times 10^-5) is titrated with NaOH, what is the pH of the solution at the half-equivalence point? PH = Start by filling in a table to express the number of moles of each species. [HA] = [A^-], the [A^-]/[HA] ratio is equal to 1. Use the Henderson - Hasselbalch equation to find pH.

Explanation / Answer

at half equivalece point moles of acid remains = moles of salt formed

so henderson -hasselbalch equation

pH = pKa + log [salt /acid]

pH = pKa

Ka = 1.0 x 10^-5

pKa = -log Ka = -log (1.0 x 10^-5)

pKa = 5.0

pH = pKa =5.0

pH = 5.0 -------------------------> answer