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Using the graph below, determine the pK, of the weak acid. Titration Curve pH versus ml Sodium Hydroxide added 13.00 12.00 11.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0.0 5.0 10.0 15.0 20.0 25.0 mL of sodium hydroxide Select one: O 4.5 O 5.24 O 4.52 O 8.72 O 10.1 O 4.1

Using the graph below, determine the pK, of the weak acid. Titration Curve pH versus ml Sodium Hydroxide added 13.00 12.00 11.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0.0 5.0 10.0 15.0 20.0 25.0 mL of sodium hydroxide Select one: O 4.5 O 5.24 O 4.52 O 8.72 O 10.1 O 4.1

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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### Determining the pKa of a Weak Acid Using a Titration Curve #### Introduction: Titrations are a fundamental method in analytical chemistry used to determine the concentration of an unknown acid or base by neutralizing it with a base or acid of known concentration. The point at which neutralization occurs can be observed and utilized to calculate the pKa of a weak acid. #### Titration Curve Explanation: The graph displayed shows a titration curve of a weak acid being titrated with sodium hydroxide (NaOH). The x-axis represents the volume of sodium hydroxide added in milliliters (mL), ranging from 0 to 25. The y-axis represents the pH, ranging from 0 to 13. Each black dot on the graph denotes the pH measurement at various volumes of added NaOH. 1. **Initial Region (0.0 - 5.0 mL)** - At the beginning of the titration, the pH starts at around 2.0 and gradually rises. This region represents the presence of a weak acid. 2. **Buffering Region (5.0 - 15.0 mL)** - From approximately 5 to 15 mL of NaOH added, the pH increases more slowly and forms a buffer region. Here, the weak acid and its conjugate base are in appreciable amounts, leading to a relatively steady pH. 3. **Equivalence Point (around 20.0 mL)** - Near 20 mL of NaOH added, there is a sharp increase in pH. The equivalence point is where the amount of NaOH added is stoichiometrically equivalent to the amount of acid present. - The steep rise in pH indicates the point where all the weak acid has been neutralized, and any further addition of NaOH results in a rapid increase in pH due to excess OH- ions in solution. 4. **Excess Base (Beyond 20.0 mL)** - Beyond the equivalence point, the solution continues to become more basic with the addition of more NaOH, and the pH increases less steeply towards a plateau at around 12.0 to 13.0. #### Determining pKa: - The pKa of the weak acid can be determined from the titration curve, specifically from the midpoint of the buffering region. This is often found at the
Transcribed Image Text:### Determining the pKa of a Weak Acid Using a Titration Curve #### Introduction: Titrations are a fundamental method in analytical chemistry used to determine the concentration of an unknown acid or base by neutralizing it with a base or acid of known concentration. The point at which neutralization occurs can be observed and utilized to calculate the pKa of a weak acid. #### Titration Curve Explanation: The graph displayed shows a titration curve of a weak acid being titrated with sodium hydroxide (NaOH). The x-axis represents the volume of sodium hydroxide added in milliliters (mL), ranging from 0 to 25. The y-axis represents the pH, ranging from 0 to 13. Each black dot on the graph denotes the pH measurement at various volumes of added NaOH. 1. **Initial Region (0.0 - 5.0 mL)** - At the beginning of the titration, the pH starts at around 2.0 and gradually rises. This region represents the presence of a weak acid. 2. **Buffering Region (5.0 - 15.0 mL)** - From approximately 5 to 15 mL of NaOH added, the pH increases more slowly and forms a buffer region. Here, the weak acid and its conjugate base are in appreciable amounts, leading to a relatively steady pH. 3. **Equivalence Point (around 20.0 mL)** - Near 20 mL of NaOH added, there is a sharp increase in pH. The equivalence point is where the amount of NaOH added is stoichiometrically equivalent to the amount of acid present. - The steep rise in pH indicates the point where all the weak acid has been neutralized, and any further addition of NaOH results in a rapid increase in pH due to excess OH- ions in solution. 4. **Excess Base (Beyond 20.0 mL)** - Beyond the equivalence point, the solution continues to become more basic with the addition of more NaOH, and the pH increases less steeply towards a plateau at around 12.0 to 13.0. #### Determining pKa: - The pKa of the weak acid can be determined from the titration curve, specifically from the midpoint of the buffering region. This is often found at the
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