t, University of Oklahoma 1G You Are Asked To Prepa . D now with 33% more hon x
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t, University of Oklahoma 1G You Are Asked To Prepa . D now with 33% more hon x ? COwww.s ibiscms/mod/ibis/view.php?id-4905064 Sapling Learning Kathleen Kenney Jump to.. macrTIlan leernng Sapling Learning University of Oklahoma -CHEM 1415-Spring18-CLIFFORD, YIP Activities and Due DatesHW-11 My Assignment Resources # Attempts Score 04/6/2018 11:55 PM 048/5 Gradebook O Assignment Information Print Cakulator- Periccic Table Quesion 10 of 18 Available From 3/30/2018 06:00 PM Due Date Points Possible: 5 Grade Category. Homework Map 416/2018 11:55 PM Sapling Learning You are asked to prepare 500. mL of a 0.200 M acetate buffer st pH 4.90 using only pure acetic acid (MW-60.05 gmol, pk, 4.76), 3.00 M NaOH, and water. Answer the following questions regarding the preparation of the buffer 1. How many grams of acatic acid will you need to prepare the 500 mL buffer? Note that the given concentration or a attempt. 0% penalty. Policies: Solutions After Due Date refers to the concentration of ail acetate species in solution. Number 2.52 You can check your answers. You can view solutions after the due date. You have five attempts per question. There is no penalty for incorrect answers. 2. What vclume af 3.00 M NaOH must you add to the acetic acid to achieve a butfer with a pH of 4.90 at a final volume of 500 mL? (Ignore activity coefficients.) 10 3 11 4 12 O eTextbook 20.0 Help With This Topic 13 1 14 2 15 1 16 2 3. Pour the beaker contents into a 500 mL volumetric flask. Rinse the beaker several times and add the rinses to the flask, Swirl the flask to mix the solution. Add water to the mark to make the volume 500 mL. Stopper the flask and invert how many times to ensure complete mixing? O Web Help & Videos O Technical Support and Bug Reports In?rrect 17 1 O Previous #Try Again Next Exit Explanation 18 1 e 2011-2018Sapling Leaming, lic about us carosrspiacy policy terms of usecontact us help 0 Type here to search 12:57 PM 4/5/2018Explanation / Answer
--calculations---
pKa of acetic acid = 4.76
Total required conc. of acetate + acetic acid = 0.200 M
pH = pKa + log[B]/[BH]
pH req = 4.90 = 4.76 + log[B]/[BH],
log[B]/[BH] = 0.14
[B]/[BH] =1.380
[B] + [BH] = 0.200 M
On solving, [B] = 0.1159 M, [BH] = 0.0840 M
i.e. [acetate] = 0.1159 M and [acetic acid] = 0.0840 M
To make 0.2 M, 500 mL acetic acid,
Molecular mass = 60.05, 0.2 M/500 mL = 60.05 x 0.2/2 = 6.05 g of acetic acid
The molarity of acetate ions in 0.2 M buffer at pH 4.9 = 0.1159 M
So the molarity of NaOH needs to be added = 0.1159 M
So the volume required to add 3 M NaOH to make the 500 mL buffer =
0.1159 x 500/3 = 19.3167 mL
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