Acid-Base Titration Curves in Analytical Chemistry

Acid-Base Titration Curves

Acid-base titration curves show the progress of titration as a function of the volume of titrant added, providing a visual picture of how a property, such as pH, changes during the titration.
The equivalence point is characterized by a pH level that is a function of the acid-base strengths and concentrations of the analyte and titrant.

Titration of Strong Acids and Strong Bases

When titrating a strong acid (HCl) with a strong base (NaOH), the only equilibrium reaction of importance is H3O+ (aq) + OH- (aq) → 2H2O (l).
At the equivalence point, the moles of HCl and NaOH are equal, and the pH is determined by the dissociation of water, resulting in a pH of 7.00.
Before the equivalence point, the pH is determined by the concentration of unreacted HCl, and after the equivalence point, the pH is determined by the excess OH-.

Construction of Titration Curves

To construct a titration curve, calculate the volume of titrant needed to reach the equivalence point, and then calculate the pH at various points before and after the equivalence point.
Use the equilibrium calculations described in previous lectures to determine the pH at each point.

Acid-Base Applications

Acid-base titrations are used in the analysis of inorganic and organic compounds, with an emphasis on applications in environmental and clinical analysis.
Inorganic analysis uses acid-base titrations to determine the concentration of inorganic acids and bases, such as H3PO4, H3BO3, and H3AsO4, and inorganic bases, such as Na2CO3, NaHCO3, and mixtures of both.
Environmental analysis uses acid-base titrations to determine the alkalinity (OH-, HCO3-, and CO32-), acidity (HCl, HNO3, and H2SO4), and free CO2 in waters and wastewaters.

Determination of Carbonate in a Mixture

Acid-base titrations can be used to determine the concentration of carbonate in a mixture of carbonate and bicarbonate using two indicators and a standard HCl solution.
The volume of HCl required for ½ of the carbonate can be determined, and then the volume of HCl required for the entire carbonate can be calculated.

Organic Analysis

Acid-base titrations are used in the analysis of organic compounds, particularly in the Kjeldahl analysis for organic nitrogen.
Examples of analytes determined by a Kjeldahl analysis include caffeine and saccharin in pharmaceutical products, proteins in foods, and nitrogen in fertilizers, sludges, and sediments.

Kjeldahl Analysis

The Kjeldahl analysis is a quantitative method for determining the %w/w N in a sample, which is then converted to %w/w protein using a conversion factor.
The method involves oxidizing the nitrogen in the sample to NH4+, and then distilling the ammonia into a flask containing a known amount of standard strong acid, followed by back titration with a standard strong base titrant.
The benefits of the Kjeldahl method include high precision and reproducibility, high productivity, and affordability.

Acid-Base Titration Curves

Acid-base titration curves show the progress of titration as a function of the volume of titrant added, providing a visual picture of how a property, such as pH, changes during the titration.
The equivalence point is characterized by a pH level that is a function of the acid-base strengths and concentrations of the analyte and titrant.

Titration of Strong Acids and Strong Bases

When titrating a strong acid (HCl) with a strong base (NaOH), the only equilibrium reaction of importance is H3O+ (aq) + OH- (aq) → 2H2O (l).
At the equivalence point, the moles of HCl and NaOH are equal, and the pH is determined by the dissociation of water, resulting in a pH of 7.00.
Before the equivalence point, the pH is determined by the concentration of unreacted HCl, and after the equivalence point, the pH is determined by the excess OH-.

Construction of Titration Curves

To construct a titration curve, calculate the volume of titrant needed to reach the equivalence point, and then calculate the pH at various points before and after the equivalence point.
Use the equilibrium calculations described in previous lectures to determine the pH at each point.

Acid-Base Applications

Acid-base titrations are used in the analysis of inorganic and organic compounds, with an emphasis on applications in environmental and clinical analysis.
Inorganic analysis uses acid-base titrations to determine the concentration of inorganic acids and bases, such as H3PO4, H3BO3, and H3AsO4, and inorganic bases, such as Na2CO3, NaHCO3, and mixtures of both.
Environmental analysis uses acid-base titrations to determine the alkalinity (OH-, HCO3-, and CO32-), acidity (HCl, HNO3, and H2SO4), and free CO2 in waters and wastewaters.

Determination of Carbonate in a Mixture

Acid-base titrations can be used to determine the concentration of carbonate in a mixture of carbonate and bicarbonate using two indicators and a standard HCl solution.
The volume of HCl required for ½ of the carbonate can be determined, and then the volume of HCl required for the entire carbonate can be calculated.

Organic Analysis

Acid-base titrations are used in the analysis of organic compounds, particularly in the Kjeldahl analysis for organic nitrogen.
Examples of analytes determined by a Kjeldahl analysis include caffeine and saccharin in pharmaceutical products, proteins in foods, and nitrogen in fertilizers, sludges, and sediments.

Kjeldahl Analysis

The Kjeldahl analysis is a quantitative method for determining the %w/w N in a sample, which is then converted to %w/w protein using a conversion factor.
The method involves oxidizing the nitrogen in the sample to NH4+, and then distilling the ammonia into a flask containing a known amount of standard strong acid, followed by back titration with a standard strong base titrant.
The benefits of the Kjeldahl method include high precision and reproducibility, high productivity, and affordability.

Acid-Base Titration Curves

Acid-base titration curves show the progress of titration as a function of the volume of titrant added, providing a visual picture of how a property, such as pH, changes during the titration.
The equivalence point is characterized by a pH level that is a function of the acid-base strengths and concentrations of the analyte and titrant.

Titration of Strong Acids and Strong Bases

When titrating a strong acid (HCl) with a strong base (NaOH), the only equilibrium reaction of importance is H3O+ (aq) + OH- (aq) → 2H2O (l).
At the equivalence point, the moles of HCl and NaOH are equal, and the pH is determined by the dissociation of water, resulting in a pH of 7.00.
Before the equivalence point, the pH is determined by the concentration of unreacted HCl, and after the equivalence point, the pH is determined by the excess OH-.

Construction of Titration Curves

To construct a titration curve, calculate the volume of titrant needed to reach the equivalence point, and then calculate the pH at various points before and after the equivalence point.
Use the equilibrium calculations described in previous lectures to determine the pH at each point.

Acid-Base Applications

Acid-base titrations are used in the analysis of inorganic and organic compounds, with an emphasis on applications in environmental and clinical analysis.
Inorganic analysis uses acid-base titrations to determine the concentration of inorganic acids and bases, such as H3PO4, H3BO3, and H3AsO4, and inorganic bases, such as Na2CO3, NaHCO3, and mixtures of both.
Environmental analysis uses acid-base titrations to determine the alkalinity (OH-, HCO3-, and CO32-), acidity (HCl, HNO3, and H2SO4), and free CO2 in waters and wastewaters.

Determination of Carbonate in a Mixture

Acid-base titrations can be used to determine the concentration of carbonate in a mixture of carbonate and bicarbonate using two indicators and a standard HCl solution.
The volume of HCl required for ½ of the carbonate can be determined, and then the volume of HCl required for the entire carbonate can be calculated.

Organic Analysis

Acid-base titrations are used in the analysis of organic compounds, particularly in the Kjeldahl analysis for organic nitrogen.
Examples of analytes determined by a Kjeldahl analysis include caffeine and saccharin in pharmaceutical products, proteins in foods, and nitrogen in fertilizers, sludges, and sediments.

Kjeldahl Analysis

The Kjeldahl analysis is a quantitative method for determining the %w/w N in a sample, which is then converted to %w/w protein using a conversion factor.
The method involves oxidizing the nitrogen in the sample to NH4+, and then distilling the ammonia into a flask containing a known amount of standard strong acid, followed by back titration with a standard strong base titrant.
The benefits of the Kjeldahl method include high precision and reproducibility, high productivity, and affordability.