Classification of experimental methods in solution chemistry

McCarthy, Patrick

doi:10.1021/ed063p339

Cited by 3 publications

(2 citation statements)

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“…The method of continuous variation, or Job’s method as it is commonly called, has been commonly used in laboratory experiments in instrumental analysis classes to determine metal-to-ligand ratios in complex formation reactions. − In the technique, the total amount of ligand and metal are held constant in a series of solutions of constant volume, whereas the individual amounts of ligand and metal are varied continuously. A physical property, such as the absorbance of the colored complex, is measured for every solution.…”

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The Method of Continuous Variation: A Laboratory Investigation of the Formula of a Precipitate

2013

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The method of continuous variation is applied to the reaction between barium chloride and diammonium hydrogen phosphate in neutral, acidic, and basic conditions. Depending on the medium, barium dihydrogen phosphate, barium hydrogen phosphate, or barium phosphate is precipitated. The precipitates are washed, dried, and weighed. Construction of a continuous variation plot for each condition leads to the deduction of the molecular formula of the phosphate precipitated. This experiment demonstrates the concept of stoichiometric relationships between ions in the formation of compounds and serves to give students practice in calculations involving limiting reagents.

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The Method of Continuous Variation: A Laboratory Investigation of the Formula of a Precipitate

2013

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“…Finally, the concept of mapping experimental paths onto a composition grid forces students to consider the sequence of compositional changes that relate to procedures carried out on a system . The redox paths shown in this paper that correspond to cell discharges form paths that angle across the grid with negative slopes.…”

Section: Some Additional Teaching Points With Nernst Surfacesmentioning

confidence: 99%

Why Batteries Deliver a Fairly Constant Voltage until Dead

2012

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Two characteristics of batteries, their delivery of nearly constant voltage and their rapid failure, are explained through a visual examination of the Nernst equation. Two Galvanic cells are described in detail: (1) a wet cell involving iron and copper salts and (2) a mercury oxide dry cell. A complete description of the wet cell requires a three-dimensional Nernst surface because the potential is a function of two variables: the activities of both the oxidized and reduced forms in each redox couple. Dry cell potentials, which utilize solid or pure liquid species, are functions of only one variable and can be described by a pair of traces in a traditional plot. Plots of the Nernst potential are relatively flat for most activities, but they exhibit cliffs under extreme conditions. The flat spots are responsible for the fairly constant voltage that batteries deliver; the cliffs explain why batteries fail so quickly.

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Discriminating Influence of α‐ and Methylated β‐Cyclodextrins on Complexation and Polymerization of Diacrylate and Dimethacrylate Monomers

Sarvothaman¹,

Ritter²

2004

Macromol. Rapid Commun.

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Summary: Host‐guest complexes of α‐cyclodextrin (α‐CD) and methylated β‐cyclodextrin (Me‐β‐CD) with diacrylates and dimethacrylates of butan‐1,4‐diol and hexan‐1,6‐diol at varying stoichiometries were studied. The complexes were analyzed by means of 1H NMR, two‐dimensional ROESY spectroscopy and Job's curves, which clearly revealed the discriminating influence of the two hosts towards complex formation. The corresponding polymers were obtained using a redox initiator system in water. Thermal analysis and IR measurements of the polymers provided evidence for the existence of a polyrotaxane architecture.Proposed structure of the cross‐linked polymers obtained by the redox polymerization of the Me‐β‐CD complexed monomers.imageProposed structure of the cross‐linked polymers obtained by the redox polymerization of the Me‐β‐CD complexed monomers.

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Classification of experimental methods in solution chemistry

Abstract: The objective of this paper is to classify the various methods used to study solution chemistry within a unified framework that clearly demonstrates the relationships and distinctions among the various techniques.

Cited by 3 publications

References 5 publications

The Method of Continuous Variation: A Laboratory Investigation of the Formula of a Precipitate

The Method of Continuous Variation: A Laboratory Investigation of the Formula of a Precipitate

Why Batteries Deliver a Fairly Constant Voltage until Dead

Discriminating Influence of α‐ and Methylated β‐Cyclodextrins on Complexation and Polymerization of Diacrylate and Dimethacrylate Monomers

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