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Related Concept Videos

Extraction: Advanced Methods00:56

Extraction: Advanced Methods

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Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is...
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Complexometric Titration: Ligands00:43

Complexometric Titration: Ligands

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Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
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Composition of Polyprotic Acid Solutions as a Function of pH01:19

Composition of Polyprotic Acid Solutions as a Function of pH

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Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of...
739
Complexation Equilibria: Factors Influencing Stability of Complexes01:09

Complexation Equilibria: Factors Influencing Stability of Complexes

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In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
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Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

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In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
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Qualitative Analysis03:46

Qualitative Analysis

23.4K
For solutions containing mixtures of different cations, the identity of each cation can be determined by qualitative analysis. This technique involves a series of selective precipitations with different chemical reagents, each reaction producing a characteristic precipitate for a specific group of cations. Metal ions within a group are further separated by varying the pH, heating the mixture to redissolve a precipitate, or adding other reagents to form complex ions.
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High Resolution Physical Characterization of Single Metallic Nanoparticles
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Polyoxometalates in solution: speciation under spotlight.

Nadiia I Gumerova1, Annette Rompel

  • 1Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstr. 14, 1090 Vienna, Austria. annette.rompel@univie.ac.at.

Chemical Society Reviews
|September 29, 2020
PubMed
Summary
This summary is machine-generated.

Understanding polyoxometalates (POMs) in solution is key for their application. This review details POM speciation, stability, and transformations, providing essential data for researchers.

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Area of Science:

  • Inorganic Chemistry
  • Materials Science
  • Solution Chemistry

Background:

  • Polyoxometalates (POMs) are anionic metal-oxo clusters with versatile structures.
  • Aqueous POM solutions contain numerous, highly charged species, complicating activity determination.
  • Identifying individual speciation profiles is crucial for successful POM application.

Purpose of the Study:

  • To review and summarize species in aqueous isopoly- and heteropolyvanadate, -niobate, -molybdate, and -tungstate solutions.
  • To present comprehensive ion-distribution diagrams across a wide pH range.
  • To provide a reference for understanding POM solution composition and guiding targeted applications.

Main Methods:

  • Literature review of existing studies on POM speciation.
  • Compilation and presentation of stability and transformation data for various POMs.
  • Generation of ion-distribution diagrams illustrating species equilibrium at different pH values.

Main Results:

  • Detailed summary of POM species present in aqueous solutions of vanadates, niobates, molybdates, and tungstates.
  • Presentation of ion-distribution diagrams showing species stability and transformations over a broad pH range.
  • Examples of how speciation studies have elucidated POM roles in various applications.

Conclusions:

  • Accurate POM speciation data is essential for understanding and optimizing their use in diverse fields.
  • The presented diagrams serve as a valuable resource for chemists and material scientists.
  • Encourages further speciation studies to advance POM applications in catalysis, nanochemistry, and medicine.