Buffer Preparation
Name:
Part A - Measuring pH
(record concentrations based on pH measurements with 3 sig figs)
Solution pH Calculated
[H+]
pOH Calculated
[OH-]
1.0M Acetic Acid
1.0M Sodium Acetate
1.0M Ammonia
1.0M Ammonium Chloride
1.0M Phosphoric Acid
1.0M Sodium Phosphate
Distilled Water
Distilled Water + 1.0M HCl
Distilled Water + 1.0M NaOH
Acetate Buffer
Acetate Buffer + 1.0M HCl
Acetate Buffer + 1.0M NaOH
Ammonia Buffer
Ammonia Buffer + 1.0M HCl
Ammonia Buffer + 1.0M NaOH
Phosphate Buffer
Phosphate Buffer + 1.0M HCl
Phosphate Buffer + 1.0M NaOH
Calculations
#1). Use your pH value to calculate the [H+] of the 1.0M Acetic Acid. Show your work.
#2). What is the % Ionization of Acetic acid? Show your work.
#3). Use your pH value to calculate the [Acetate] of the 1.0M Acetic Acid. Show your work.
#4). What is the calculated Ka for Acetic Acid? Show your work
#5). Use your pH value to calculate the [NH+] of the 1.0M Ammonia. Show your work.
#6). What is the % Ionization of Ammonia? Show your work.
#7). What is the calculated Kb for Ammonia? Show your work.
#8). If you were to add 2.1500g of solid Sodium Acetate Trihydrate to 100.00mL
your Acetate buffer solution, complete the following questions and ICE table.
8a). How many moles of Acetate ion are added? Show your work.
8b). What is the molarity of these additional acetate ions? Show your work
8c). What is the initial pH of your Acetate Buffer?
[CH3COOH] [CH3COO-] [H+]
Eq. Conc. Of
Acetate Buffer
Additional Acetate
(I)nitial
(C)hange
(E)quili
ium
Complete the ICE above table. Show your work. You may need to use the Quadratic Formula.
What is the Final pH of new solution: _____________
#9. Would the resulting solution still be a Buffer? Yes or No, explain your answer.
Part B - Preparing & Testing Buffers
Complete the Table of Conjugate Acids & Bases
Complete the table below by indicating the conjugate base for the given conjugate acid and the
conjugate acid for the given conjugate base.
Conjugate Acids Conjugate Bases
Name Formula Name Formula
Acetate
Nitric Acid
Dihydrogen Phosphate
Dihydrogen Phosphate
H2O
Water
NH4+
Buffering Capacity
Complete the table below to determine which is the better buffer for the given conditions
Acetate Buffer Phosphate Buffer Ammonia Buffer
Initial pH
pH After Adding HCl
Change in pH
pH After Adding NaOH
Change in pH
#10). Which buffer has a better buffering capacity for bases? Explain your answer.
#11). Which buffer has a better buffering capacity for acids? Explain your answer.
Part C – Titration of Phosphoric Acid
Obtain the pH of Phosphoric Acid after each addition of NaOH
Volume of
NaOH
pH Volume of
NaOH
pH
0.00mL 13.00mL
1.00mL 14.00mL
2.00mL 15.00mL
3.00mL 16.00mL
4.00mL 17.00mL
5.00mL 18.00mL
6.00mL 19.00mL
7.00mL 20.00mL
8.00mL 21.00mL
9.00mL 22.00mL
10.00mL 23.00mL
11.00mL 24.00mL
12.00mL 25.00mL
Prepare a graph of pH on the Y-Axis vs mols NaOH on the X-Axis
#16). What is the first Equivalence Point in the Titration Curve?
#17). What is the net ionic equation for the first step in the titration curve?
#18). What is the second Equivalence Point in the Titration Curve?
#19). What is the net ionic equation for the second step in the titration curve?
Attach your graph below
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What is the Final pH of new solution:
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Image131_af_image:
http:
chemcollective.org/vla
99
stimulation link for buffer preparation.
https:
www.youtube.com/watch?v=cp5KRbkgo-Y
uffer preparation video.