Ch.16 - Aqueous Equilibrium WorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Buffer
Acid and Base Titration Curves
Weak Acid Strong Base Titrations
Weak Base Strong Acid Titrations
Strong Acid Strong Base Titrations
Titrations of Diprotic and Polyprotic Acids
Ksp
Additional Practice
Equivalence Point
Acid Base Indicators
Selective Precipitation
Formation Constant
Additional Guides
Henderson Hasselbalch Equation
LearnAdditional Practice
Next SectionKsp

A diprotic or polyprotic buffer can be approached in a way similar to monoprotic buffers. The key difference is that multiple pKa values will be involved. 

Diprotic & Polyprotic Buffers

Concept #1: Diprotic & Polyprotic Buffers

Concept #2: Diprotic & Polyprotic Buffers

Concept #3: Diprotic & Polyprotic Buffers

Example #1: Calculate the pH of 100 mL of a 0.25 M H2CO3 when 70.0 mL of 0.25 M NaOH are added. Ka1 = 4.3 x 10-7 and Ka2 = 5.6 x 10-11. 

Example #2: Calculate the pH of 75.0 mL of a 0.10 M of phosphorous acid, H3PO3, when 80.0 mL of 0.15 M NaOH are added. Ka1 = 5.0 x 10-2, Ka2 = 2.0 x 10-7. 

Previous SectionStrong Acid Strong Base Titrations
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Additional Problems
A 0.868 -g sample of an unknown acid requires 32.6 mL of a 0.186 M barium hydroxide solution for neutralization.Assuming the acid is diprotic, calculate the molar mass of the acid.
A 26.0 -mL volume of a sodium hydroxide solution requires 19.6 mL of a 0.190 M hydrochloric acid for neutralization. A 12.0 -mL volume of a phosphoric acid solution requires 34.9 mL of the sodium hydroxide solution for complete neutralization.Calculate the concentration of the phosphoric acid solution.
The titration of a polyprotic acid with sufficiently different pKas displays two equivalence points. Why?
In the titration of a polyprotic acid, the volume required to reach the first equivalence point is identical to the volume required to reach the second one. Why?
Match the following descriptions of titration curves with the diagrams.strong base added to poly-protic acid
21.0 mL of 0.115 M sulfurous acid (H2 SO3 ) was titrated with 0.1015 M KOH.At what added volume of base does the first equivalence point occur?
21.0 mL of 0.115 M sulfurous acid (H2 SO3 ) was titrated with 0.1015 M KOH.At what added volume of base does the second equivalence point occur?
For the following polyprotic acid questions: Citric acid (H3C6H5O6)          K a1 = 8.4 x 10–4            K a2 = 1.8 x 10–5            K a3 = 4.0 x 10–6 Oxalic acid (H2C2O4)             K a1 = 6.5 x 10–2            K a2 = 6.1 x 10–5Sketch a titration curve of the complete titration oxalic acid with NaOH. Label the important points on the curve and list the dominant species present at each of these points.
What anion is present at the first equivalence point in the titration of H  3PO4 with NaOH?a. H2PO4-b. HPO42-c. PO43-d. PO33-e. P3-
The following plot below shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid H2A with NaOH. Which point(s) a-d represent(s) the H 2X/HX - buffer region?(a) point a(b) point b(c) point c(d) point d(e) points a and c
Find the pH of the equivalence point(s) and the volume (mL) of 0.0372 M NaOH needed to reach the point(s) in titrations of(b) 28.9 mL of 0.0850 M H 2SO3 (two equivalence points)
Find the pH of the equivalence point(s) and the volume (mL) of 0.0588 M KOH needed to reach the point(s) in titrations of(b) 17.3 mL of 0.130 M H 2CO3 (two equivalence points)
A 0.210-g sample of an acid (molar mass = 192 g/mol) is titrated with 30.5 mL of 0.108 M NaOH to a phenolphthalein end point. Is the acid monoprotic, diprotic, or triprotic?
An ecobotanist separates the components of a tropical bark extract by chromatography. She discovers a large proportion of quinidine, a dextrorotatory isomer of quinine used for control of arrhythmic heartbeat. Quinidine has two basic nitrogens (Kb1 = 4.0 × 10−6 and Kb2 = 1.0 × 10−10). To measure the concentration of quinidine, she carries out a titration. Because of the low solubility of quinidine, she first protonates both nitrogens with excess HCl and titrates the acidified solution with standardized base. A 33.85-mg sample of quinidine (ℳ = 324.41 g/mol) is acidified with 6.55 mL of 0.150 M HCl.(b) How many additional milliliters of titrant are needed to reach the first equivalence point of quinidine dihydrochloride?
An ecobotanist separates the components of a tropical bark extract by chromatography. She discovers a large proportion of quinidine, a dextrorotatory isomer of quinine used for control of arrhythmic heartbeat. Quinidine has two basic nitrogens (Kb1 = 4.0 × 10−6 and Kb2 = 1.0 × 10−10). To measure the concentration of quinidine, she carries out a titration. Because of the low solubility of quinidine, she first protonates both nitrogens with excess HCl and titrates the acidified solution with standardized base. A 33.85-mg sample of quinidine (ℳ = 324.41 g/mol) is acidified with 6.55 mL of 0.150 M HCl.(c) What is the pH at the first equivalence point?
21.0 mL of 0.126 M diprotic acid (H2A) was titrated with 0.1019 M KOH. The acid ionization constants for the acid are Ka1 = 5.2 x 10–5 and Ka2 = 3.4 x 10–10.At what added volume of base does the first equivalence point occur?
21.0 mL of 0.126 M diprotic acid (H2A) was titrated with 0.1019 M KOH. The acid ionization constants for the acid are Ka1 = 5.2 x 10–5 and Ka2 = 3.4 x 10–10.At what added volume of base does the second equivalence point occur?
Enter your answer in the provided box. If 29.11 mL of a standard 0.4926 M NaOH solution is required to neutralize 47.58 mL of H  2SO4, what is the molarity of the acid solution?
You are given solutions of HCl and NaOH and must determine their concentrations. You use 67.9 mL of NaOH to titrate 100. mL of HC1 and 32.5 mL of NaOH to titrate 50.0 mL of 0.0782 M H2SO4. Find the unknown concentrations. 
What is the molarity of a solution that contains 0.958 g of H 3PO4 in 140. mL of solution? How many milliliters of this solution could be completely neutralized by 10.59 mL of 0.449 M NaOH? 
Consider these three titrations: (i) the titration of 25.0 mL of a 0.100 M monoprotic weak acid with 0.100 M NaOH (ii) the titration of 25.0 mL of a 0.100 M diprotic weak acid with 0.100 M NaOH (iii) the titration of 25.0 mL of a 0.100 M strong acid with 0.100 M NaOH Which of the following statements is true? All three titrations have the same pH at their first equivalence point. All three titrations require the same volume of NaOH to reach their first equivalence point. All three titrations have the same the initial pH. 
If 32.0 mL of a 0.166 M NaOH solution is required to titrate 16.5 mL of a solution of H2SO4, what is the molarity of the H2SO4 solution? H2SO4 (aq) + 2NaOH (aq) → 2H2O (l) + Na2SO4 (aq) Express your answer with the appropriate units.
The flask shown here contains 0.365 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.220 M NaOH. What volume (mL) of base is needed to reach the end point of the titration? What is the molar mass (g/mol) of the acid (assuming it is diprotic and that the end point corresponds to the second equivalence point)?