Alabama State Unrversit X G chemistry question I Che \\ Alabama State Universit

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Alabama State Unrversit X G chemistry question I Che Alabama State Universit x-e Alabama New Tab d www.saplinglearning.com/ibiscms/mod/ibis/view.php?id=4589196 C Q Sapling Learning macmilan learming ::: Apps Scholarship Award fc Scholarship Opportu "Hit the Books" Scho Print Caloulator Poriadic Table Question 12 of 20 Available From: Due Date: Points Possible: Grade Category: 3/2/2018 11:00 AM 3/6/2018 11:59 PM 100 Quiz 4 Map ot What concentrations facetic acid pKa = 4.76) and acetate would be required to prepare a0.20 M buffer solution at pH 4.5? Note that the concentration and/or pH value may differ from that in the first question. STRATEGY 1. Rearrange the Henderson-Hassebalch equation to solve for the ratio of base (acetate) to acid (acetic Policies: Quiz acid), [A 2. Use the mole 3. Calculate the concentration of acetic acid. of acetate to calculate the concentration of acetate. 10 You can check your answers. You can view solutions after the due date. You have three attempts per question There is no penalty for incorrect answers. 11 0 12 0 13 0 14 0 15 0 16 0 17 0 18 0 19 0 20 0 Step 1: Rearrange the Henderson Hasselbalch equation to solve for HA pH-pK, eTextbook HA Use the Henderson-Hasselbaich equation to solve for if the solution is at pH 4.5. HA Help With This Topic Enter your answer as a number. For exampie, 9.6. Do not enter a formula like 106-2 HA Web Help& videos D Technical Support and Bug Reports Previous Check Answer Next Exit 2-31 PM O Type here to search

Explanation / Answer

Answer

[Acetate]= 0.0709M

[Acetic acid] = 0.1291M

[Acetate]/[Acetic acid] = 0.5495

Explanation

Henderson-Hasselbalch equation is

pH = pKa + log([A-] /[HA])

Rearranging Henderson-Hasselbalch equation

log([A-] /[HA]) = pH - pKa

[A-] /[HA] = 10pH - pKa

pH = 4.5

pKa = 4.76

Therefore,

[A-] /[HA] = 104.5 - 4.76

   [A-] /[HA] = 10-0.26

   [A-] /[HA] = 0.5495

[A-] = 0.5495[HA]

Total buffer concentration = 0.2M

Therefore,

[HA] + 0.5495[HA] = 0.20M

1.5495[HA] = 0.20M

[HA] = 0.1291M

so,

[A-] = 0.20M - 0.1291M = 0.0709M

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