The Modern Student Laboratory: Determination of the Thermodynamic Dissociation Constant of a Weak Acid by Potentiometric Acid-Base Titration: A Three-Hour Laboratory Experiment

Partanen, Jaako I.; Karki, Merja H.

doi:10.1021/ed071pa120

Cited by 3 publications

(3 citation statements)

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“…The pH of the distal colon of fed healthy adults is reported to be approximately 8.1 (35). Table 3 provides pKa' data for buffers relative to this target pH range (3,9,16,17,25,34,(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47). The buffers listed first are those included in the formulations for the simulated biological fluids provided in Marques et al (3) and Klein (9).…”

Section: Relationship Between the Target Dissolution Media Ph And Bufmentioning

confidence: 99%

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Mauger¹

2017

Dissolution Technol.

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Although aqueous buffers alone cannot be expected to fulfill all the requirements of biorelevant media, buffers will likely continue to play a central role in controlling the pH of complex formulations simulating biological fluids (3,9). The use of biorelevant dissolution media to forecast in vivo drug performance has been reviewed (9). This minireview focuses on the physicochemical factors related to buffers used in these media and not the biorelevant dissolution media, per se. This mini-review is based on a survey of the literature associated with buffers in general ABSTRACTThis literature review focuses on the physicochemical properties of buffers used in biorelevant media for in vitro dissolution testing. Because biorelevant dissolution systems have been previously reviewed, this review is primarily related to the buffers used in biorelevant media and not the media, per se. It is based on a survey of the literature in areas including analytical chemistry; biochemistry; clinical, solution, and physical chemistry; dissolution science and technology; pharmaceutical sciences; simulated biological fluids; and buffer-related articles from the National Institute of Standards and Technology with the intent of identifying challenges in formulating buffered biorelevant dissolution media and also identifying general attributes that are useful in selecting a buffer for a particular dissolution application. Other topics include: (1) key physicochemical properties of buffers that affect experimental conditions and dissolution results; (2) buffer compatibility with a diverse array of ingredients found in biorelevant media; and (3) the potential to supplement the library of traditional buffers used for in vitro dissolution testing with zwitterionic buffers that were designed for biological application.

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Section: Relationship Between the Target Dissolution Media Ph And Bufmentioning

confidence: 99%

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Mauger¹

2017

Dissolution Technol.

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“…The goal for students is to verify Hess's law using the evaluated experimental values of Δ r H, Δ n H, and Δ d H. Through this inquiry activity, students understand the thermochemical relationship in the multistep chemical process by experiencing the calorimetric measurement 3 and determination of dissociation constant. 4,5 In this study, the experimental procedures and data treatment are described in line with our practice at an inquiry The calorimetric vessel and a sensitive thermometer of sufficient precision are selected according to the expectations for the experiment. For more accurate calorimetric measurements, a calorimetric vessel with a higher thermal insulation is recommended to minimize thermal leakage.…”

mentioning

confidence: 99%

“…The goal for students is to verify Hess’s law using the evaluated experimental values of Δ r H , Δ n H , and Δ d H . Through this inquiry activity, students understand the thermochemical relationship in the multistep chemical process by experiencing the calorimetric measurement and determination of dissociation constant. , …”

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confidence: 99%

Neutralization and Acid Dissociation of Hydrogen Carbonate Ion: A Thermochemical Approach

et al. 2013

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A laboratory inquiry into the thermochemical relationships in the reaction between aqueous solutions of NaHCO3 and NaOH is described. The enthalpy change for this reaction, Δr H, and that for neutralization of strong acid and NaOH(aq), Δn H, are determined calorimetrically; the explanation for the difference is the basis for the student inquiry. The contribution of acid dissociation of the hydrogen carbonate ion to the overall reaction is considered by students as a possible explanation for the difference. Using Hess’s law, students propose a positive value for the acid dissociation enthalpy change Δd H. Then, they are required to show experimental evidence of the positive Δd H. Examination of the temperature dependence of the acid dissociation constant K a is performed by students through pH measurements of the solution at the half-neutralization point of the reaction between aqueous solutions of NaHCO3 and NaOH at different temperatures. This provides a second means of predicting the sign of Δd H; then, through introduction of the van’t Hoff equation, a numerical value for Δd H can be calculated. The goal of the inquiry activity is to verify Hess’s law using the evaluated experimental values of Δr H, Δn H, and Δd H. This lab activity is appropriate for advanced chemistry courses at high schools or general chemistry courses at colleges. Further, calculations of the Gibbs energy change Δd G and entropy change Δd S of acid dissociation of the hydrogen carbonate ion from the student data for the temperature dependence of K a can be applied in an advanced lab activity.

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Comparison of different methods for calculation of the stoichiometric dissociation constant of acetic acid from results of potentiometric titrations at 298.15 K in aqueous sodium or potassium chloride solutions

Partanen

Juusola

2000

Fluid Phase Equilibria

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The Modern Student Laboratory: Determination of the Thermodynamic Dissociation Constant of a Weak Acid by Potentiometric Acid-Base Titration: A Three-Hour Laboratory Experiment

Cited by 3 publications

References 1 publication

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Physicochemical Properties of Buffers Used in Simulated Biological Fluids with Potential Application for In Vitro Dissolution Testing: A Mini-review

Neutralization and Acid Dissociation of Hydrogen Carbonate Ion: A Thermochemical Approach

Comparison of different methods for calculation of the stoichiometric dissociation constant of acetic acid from results of potentiometric titrations at 298.15 K in aqueous sodium or potassium chloride solutions

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