Ka and Kb from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise

Nyasulu, Frazier; Moehring, Michael; Arthasery, Phyllis; Barlag, Rebecca

doi:10.1021/ed100132m

Cited by 10 publications

(18 citation statements)

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“…The general fundamentals of this technique are collected in Gelhaus and Lacourse (2005) [74] and Gzybkoski (2002) [75]. Its importance in the educational literature has been highlighted [76,77] and many examples have been recently published in the Journal of Chemical Education i.e., studies on sulfate determination [78]; the identification and quantification of an unknown acid [79], electrolyte polymers [80,81], acid and basic constants determinations [82], its use in general chemistry [83], microcomputer interface [84] and conductometric-potentiometric titrations [85]. An accurate method of determining conductivity in acid-base reactions [86], the acid-base properties of weak electrolytes [87], and those of polybasic organic acids [88] have also been recently subject of s tu dy.…”

Section: Application To Experimental Systemmentioning

confidence: 99%

Intersecting Straight Lines: Titrimetric Applications

Martín¹,

Martin²,

Asuero³

2017

Advances in Titration Techniques

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Plotting two straight line graphs from the experimental data and determining the point of their intersection solve a number of problems in analytical chemistry (i.e., potentiometric and conductometric titrations, the composition of metal-chelate complexes and binding interactions as ligand-protein). The relation between conductometric titration and the volume of titrant added leads to segmented linear titration curves, the endpoint being defined by the intersection of the two straight line segments. The estimation of the statistical uncertainty of the end point of intersecting straight lines is a topic scarcely treated in detail in a textbook or specialized analytical monographs. For this reason, a detailed treatment with that purpose in mind is addressed in this book chapter. The theoretical basis of a variety of methods such as first-order propagation of variance (random error propagation law), Fieller's theorem and two approaches based on intersecting confidence bands are explained in detail. Several experimental systems described in the literature are the subject of study, with the aim of gaining knowledge and experience in the application of the possible methods of uncertainty estimation. Finally, the developed theory has been applied to the conductivity measurements in triplicate in the titration of a mixture of hydrochloric acid and acetic acid with potassium hydroxide.

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Section: Application To Experimental Systemmentioning

confidence: 99%

Intersecting Straight Lines: Titrimetric Applications

Martín¹,

Martin²,

Asuero³

2017

Advances in Titration Techniques

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“…The study of the conductivity of electrolyte solutions is important for the development of electrochemical devices, 1,2 for the characterization of the dissociation equilibrium of weak electrolytes, [2][3][4] and for the fundamental understanding of charge transport by ions. 5 Therefore, experiments in general chemistry and physical chemistry laboratories are widespread in undergraduate chemistry courses, and are subject to many educational developments, from the development of conductivity measuring apparatus to the preparation and study of specific electrolytes.…”

Section: Introductionmentioning

confidence: 99%

“…5 Therefore, experiments in general chemistry and physical chemistry laboratories are widespread in undergraduate chemistry courses, and are subject to many educational developments, from the development of conductivity measuring apparatus to the preparation and study of specific electrolytes. 1,2 Typically, the conductivity of electrolyte solutions is measured for electrolyte solutions with concentrations in the range of 10 -3 to 10 -1 mol L -1 , as solutions in this range of concentrations can be easily prepared. 2,5,6 The molar conductivity (Λ m ) of strong electrolyte solutions can be nicely fit by the Kohlrausch equation, 7 (1) where is the molar conductivity at infinite dilution and c is the concentration of the solution.…”

Section: Introductionmentioning

confidence: 99%

“…1,2 Typically, the conductivity of electrolyte solutions is measured for electrolyte solutions with concentrations in the range of 10 -3 to 10 -1 mol L -1 , as solutions in this range of concentrations can be easily prepared. 2,5,6 The molar conductivity (Λ m ) of strong electrolyte solutions can be nicely fit by the Kohlrausch equation, 7 (1) where is the molar conductivity at infinite dilution and c is the concentration of the solution. K is an empirical proportionality constant to be obtained from the experiment.…”

Section: Introductionmentioning

confidence: 99%

“…The molar conductivity of weak electrolytes, on the other hand, is dependent on the degree of dissociation of the electrolyte. At the limit of very dilute solutions, the Ostwald dilution law is expected to be followed, (2) where C A is the analytical concentration of the electrolyte and K d is the dissociation constant.…”

Section: Introductionmentioning

confidence: 99%

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Measuring the Conductivity of Very Dilute Electrolyte Solutions, Drop by Drop

Martı́nez¹

2018

Quim. Nova

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Undergraduate experiments on ionic conductivity are common practice in general chemistry and advanced physical chemistry laboratories. Often, the conductivities are measured for solutions prepared for various salts, in a range of concentrations, and the relationship between solution conductivity and concentration is interpreted in terms of the Kohlrausch law. Contaminations can dominate the conductivity of the solutions such that students might obtain unsatisfactory results for analysis. Here, the experience of using a simple experimental procedure to obtain the concentration dependence of ionic conductivities for very dilute (sub-millimolar) electrolyte solutions in undergraduate laboratories is described. The experiment consists of measuring the conductivity of solutions of increasing concentration prepared by dropping the electrolyte solution into an initial vessel of deionized water. The range of concentrations achieved is one in which the conductivities vary linearly with the concentrations, such that the molar conductivities can be obtained directly without the use of the Kohlrausch equation. The simplicity of the experimental procedure leads the students to obtain good quality results using minimal amounts of materials. Examples are presented for the conductivities of strong electrolytes, and for the weak acetic acid electrolyte, for which the conductivity is dependent on the degree of dissociation also for dilute solutions.

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Thin Films of Copper (I) Iodide Doped with Iodine and Thiocyanate

DeSilva

Harwell

Gaquere-Parker

et al. 2017

Physica Status Solidi (a)

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It is found that thiocyanate (SCN) is an alternative dopant that greatly stabilizes the p‐type semiconducting properties of CuI. Thiocyanate doping can be achieved by a complete removal of the excess iodine and introduction of thiocyanate via suitable precursors at ambient temperature. A method of removal of iodine from CuI before casting films is described. The electrical and optical properties of thiocyanate‐doped CuI thin films are also discussed.

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K_a and K_b from pH and Conductivity Measurements: A General Chemistry Laboratory Exercise

Cited by 10 publications

References 1 publication

Intersecting Straight Lines: Titrimetric Applications

Intersecting Straight Lines: Titrimetric Applications

Measuring the Conductivity of Very Dilute Electrolyte Solutions, Drop by Drop

Thin Films of Copper (I) Iodide Doped with Iodine and Thiocyanate

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