18. Aqueous Equilibrium

Titrations of Diprotic and Polyprotic Acids

Polyprotic Acid-Base Part 4: Titrations & Indicators

Titrations of polyprotic acids | Acids and bases | AP Chemistry | Khan Academy

Match the following descriptions of titration curves
with the diagrams: (d) strong base added to polyprotic acid. [Section 17.3]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/a2bce966989df6ac-1667316881518.jpg" alt="" />

Consider the titration of 50.0 mL of a 0.100 M solution of
the protonated form of the amino acid alanine (H2A+: Ka1 = 4.6 x 10^-3, Ka2 = 2.0 x 10^-10) with 0.100 M NaOH. Calculate the pH after the addition of each of the following volumes of base. 
(e) 100.0 mL

A 25.0-mL volume of a sodium hydroxide solution requires 
19.6 mL of a 0.189 M hydrochloric acid for neutralization. A 
10.0-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.

Titration of Polyprotic Acids

The following pictures represent solutions at various stages in the titration of a weak diprotic acid H2A with aqueous NaOH. (Na+ ions and water molecules have been omitted for clarity.)
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/3cf2c02fac113881-1673018423212.jpg" alt="" />.
(b) Which solution has the highest pH? Which has the lowest pH?

The following pictures represent solutions at various stages in the titration of sulfuric acid H2A (A2- = SO4
2-) with aqueous NaOH. (Na+ ions and water molecules have been omitted for clarity.) 
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6716ba4dccd59ba9-1673391172402.jpg" alt="" />.
(b) Which solution has the highest pH? Draw a picture that represents the solution prior to addition of any NaOH.

Diprotic & Polyprotic Buffers

The pH titration curve applies to the titration of 40.0 mL of a 0.100 M solution of an acid with 0.100 M NaOH. What are the approximate pKa values for this acid? <img src="https://lightcat-files.s3.amazonaws.com/problem_images/a273d4a3921b7e8d-1673299199863.jpg" alt="" /> 
(a) pKa1 = 5, pKa2 = 10
(b) pKa1 = 7, pKa2 = 11
(c) pKa1 = 5, pKa2 = 10, pKa3 = 13 
(d) pKa1 = 5, pKa2 = 7, pKa3 = 10

16.7 Polyprotic Acid Titrations

The titration of 0.02500 L of a diprotic acid solution with 0.1000 M NaOH requires 34.72 mL of titrant to reach the second equivalence point. The pH is 3.95 at the first equiva-lence point and 9.27 at the second equivalence point. If the acid solution contained 0.2015 g of the acid, what is the molar mass, pKa1, and pKa2 of the acid?

Consider the titration of 50.0 mL of a 0.100 M solution of
the protonated form of the amino acid alanine (H2A+: Ka1 = 4.6 x 10^-3, Ka2 = 2.0 x 10^-10) with 0.100 M NaOH. Calculate the pH after the addition of each of the following volumes of base. 
(d) 75.0 mL

Consider the titration of 50.0 mL of 1.00 M H3PO4 with 1.00 M KOH. Calculate the pH after the addition of each of the following volumes of base. 
(a) 25.0 mL

Acid - Base Equilibria | Polyprotic Acids Titration.

A 20.0-mL sample of 0.115 M sulfurous acid (H2SO3) solution is
titrated with 0.1014 M KOH. At what added volume of base solution
does each equivalence point occur?

A 0.867-g sample of an unknown acid requires 32.2 mL of a 
0.182 M barium hydroxide solution for neutralization. Assuming 
the acid is diprotic, calculate the molar mass of the acid.

Suppose you want to do a physiological experiment that 
calls for a pH 6.50 buffer. You find that the organism with 
which you are working is not sensitive to the weak acid 
H2A 1Ka1 = 2 * 10-2; Ka2 = 5.0 * 10-72 or its sodium 
salts. You have available a 1.0 M solution of this acid and a 
1.0 M solution of NaOH. How much of the NaOH solution 
should be added to 1.0 L of the acid to give a buffer at pH 
6.50? (Ignore any volume change.)

The following pictures represent solutions at various stages in the titration of sulfuric acid H2A (A2- = SO4
2-) with aqueous NaOH. (Na+ ions and water molecules have been omitted for clarity.) 
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6716ba4dccd59ba9-1673391172402.jpg" alt="" />.
(a) To which of the following stages do solutions 1–4 correspond? (i) Halfway to the first equivalence point (ii) Halfway between the first and second equivalence points (iii) At the second equivalence point
(iv) Beyond the second equivalence point

Consider the titration of 50.0 mL of 1.00 M H3PO4 with 1.00 M KOH. Calculate the pH after the addition of each of the following volumes of base. 
(d) 100.0 mL

Polyprotic Acids

A 30.00-mL sample of an unknown H3PO4 solution is titrated
with a 0.100 M NaOH solution. The equivalence point is
reached when 26.38 mL of NaOH solution is added. What is the
concentration of the unknown H3PO4 solution? The neutralization
reaction is
H3PO4(aq) + 3 NaOH(aq)¡3 H2O(l ) + Na3PO4(aq)

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[BOOK CHEM] Clutch Version

Weak Acid Strong Base Titrations

Whenever a WEAK ACID reacts with a STRONG BASE we use an ICF Chart to determine the pH of the solution.&#160;

Strong Acid Strong Base Titrations

In a Strong Acid-Strong Base Titration we do not use an ICF Chart or ICE Chart to determine the pH of the solution.&nbsp;

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.&#160;

Buffer

Weak Base Strong Acid Titrations

Whenever a&nbsp;WEAK BASE reacts with a&nbsp;STRONG ACID we use an&nbsp;ICF Chart to determine the pH of the solution.&nbsp;

Acid and Base Titration Curves

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