Name: solvent partitioning in chemical extraction
Uploaded: 2024-04-04T10:51:24.000Z
Duration: 1 min 14 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

Matter and Its Interactions

CHEM1.PS1.7

extraction-partition-and-distribution-coefficients

Extraction: Partition and Distribution Coefficients

על פי חוק ההתפלגות של נרנסט, בטמפרטורה קבועה, S המומס יפיץ את עצמו בין שני ממסים בלתי ניתנים להפרכה כמתואר על ידי מקדם החלוקה שלו KD.
KD של מומס שווה למקדם ההתפלגות שלו, D, אם המומס קיים בצורה כימית אחת הן בשלב הממס המימי והן בשלב הממס האורגני.
נניח שהמומס קיים בשתי צורות כימיות, A ו-B, כאשר רק A מתחלק בין שני השלבים אז, KD מבוטא כיחס הריכוז של, A בין שתי שכבות הממס. 
לעומת זאת, D שווה לריכוז של A בפאזה האורגנית חלקי הריכוז של A ו-B בפאזה המימית.
KD הוא קבוע שיווי משקל תרמודינמי עבור חלוקה מומסת ספציפית בין שני ממסים.
D תלוי pH ומשתנה בהתאם לכמות היחסית של המומס בתמיסה.
גם KD וגם D קשורים לכמות המומס העוברת משלב ממס אחד למשנהו וממלאים תפקיד חשוב בכרומטוגרפיה.

מיצוי: מקדמי חלוקה וחלוקה

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חוק ההפצה או חוק הפילוג של נרנסט הוא החוק המסדיר את חלוקתו של מומס בין שני ממסים שאינם ניתנים לערבב. חוק זה, המכונה גם חוק החלוקה, קובע שאם מוסיפים מומס לתערובת של שני ממיסים בלתי מתערבים בטמפרטורה קבועה, המומס מתחלק בין שני הממיסים באופן שהיחס בין ריכוזי המומסים בממסים נשאר קבוע בשיווי משקל.

להפקת מומס מפאזה מימית לפאזה אורגנית, ניתן לבטא מתמטית את חוק ההפצה של נרנסט כמשוואה בין מקדם החלוקה (K_D) לבין היחס בין ריכוז המומסים בפאזה האורגנית חלקי זה שבפאזה המימית. מקדם החלוקה שווה ליחס החלוקה (D) אם המומס קיים רק בצורה כימית אחת בכל שלב ממס. עם זאת, ל-K_D ול-D יש ערכים שונים אם המומס קיים ביותר מצורה כימית אחת בכל אחד משלבי הממס.

מכיוון שמקדם החלוקה הוא קבוע שיווי משקל תרמודינמי, יש לו ערך קבוע לחלוקת מומס מסוים בין שני שלבים, ללא קשר לכמות בכל שלב. לעומת זאת, ערך ההתפלגות, D, משתנה ככל שכמות המומסים בכל שלב משתנה. מקדמי החלוקה והחלוקה משפיעים על ההפרדה של מומסים בטכניקות כמו כרומטוגרפיה, שבה נדרשת חלוקה נכונה בין שני שלבים כדי להפריד את מרכיב העניין משאר התערובת.
</div>

חוק ההפצה או חוק ההפצה של נרנסט הוא החוק המסדיר את חלוקת המומס בין שני ממיסים בלתי ניתנים להפרעה. החוק הזה, גם...

Education

JoVE Core

Analytical Chemistry

כימיה אנליטית

Unit 1

יחידה 1

Introduction to Separation Methods

מבוא לשיטות הפרדה

KEY TERMS AND CONCEPTS

מונחי מפתח ומושגים

solvent partitioning in chemical extraction

Solvent partitioning in chemical extraction describes how a solute spreads between two immiscible solvents. Immiscible solvents do not mix, such as an aqueous phase and an organic phase. The distribution law, also called Nernst's distribution law or the partition law, explains how that solute is shared at a constant temperature and equilibrium.

At equilibrium, the ratio of solute concentrations in the two solvents stays constant. For extraction from water into an organic solvent, this relationship is written with the partition coefficient, K D, as the concentration in the organic phase divided by the concentration in the aqueous phase. The partition coefficient equals the distribution ratio, D, when the solute exists in only one chemical form in each phase.

K D and D can differ when the solute is present in more than one chemical form in either solvent phase. The partition coefficient is a thermodynamic equilibrium constant, so it has a fixed value for a specific solute between two phases. The distribution value, D, can change as the amount of solute in each phase changes.

These coefficients matter in separation methods such as chromatography. In chromatography, proper partitioning between two phases helps separate the component of interest from the rest of the mixture. Understanding partition and distribution coefficients helps explain why some substances move more easily into one solvent than another.

Solvent Partitioning in Chemical Extraction

solvent-partitioning-in-chemical-extraction

states of matter and phase changes

Heating and Cooling During Phase Changes

Heating and cooling can change a substance from one state of matter to another. These phase changes depend on internal energy, which is the total kinetic energy of particles and the potential energy from their interactions. In the condensed phases, stronger intermolecular forces and the pressure on the substance affect that internal energy. The internal energy is highest in the gaseous state, lowest in the solid state, and in between for the liquid state. Phase transitions happen when...

distillation: vapor&ndash;liquid equilibria

Distillation and Boiling Point Changes

Distillation separates a miscible liquid mixture by using differences in boiling points. It works best when the two liquids have a significant boiling point gap, usually at least 20°C. In this process, the mixture is heated until the more volatile component reaches its bubble point and begins to vaporize. The vapor then rises into a condenser. A condenser is a glass tube with separate inner and outer sections. Cold water flows through the outer section and cools the vapor in the inner section,...

filtration

Filtration Setup and Filtrate Collection

Filtration separates a solid from a liquid by passing a suspension through a porous medium. The solid stays on the filter, and the liquid, called the filtrate, passes through. This makes filtration a physical separation process, not a chemical change. The filtering medium is chosen for the purpose of the separation, the amount of material, and the nature of the precipitate. A good filter medium should be inert, mechanically strong, nonabsorbent toward dissolved materials, and able to let...

centrifugation

Centrifugation for Separating Particles

Centrifugation separates particles in a liquid by using differences in size and density. The sample is placed in centrifugation tubes and spun at high angular velocity. This creates centrifugal force, which makes the different components move at different rates. After spinning, the supernatant, or liquid above the settled material, is decanted. In some cases, the pellet is kept for further purification. In other cases, the supernatant is kept and may be spun again for additional processing. <br...

sublimation

Sublimation in Separation and Purification

Sublimation is the direct change of a solid into a gas. It skips the liquid state. A common example is solid carbon dioxide, or dry ice, which turns into gaseous carbon dioxide at standard pressure and room temperature. The phase diagram shows when sublimation can happen. This process occurs at the solid-gas boundary. It is not seen above the triple point of a substance. The reverse process is deposition, which is when a gas changes directly into a solid. Sublimation and deposition can help...

recrystallization: solid&ndash;solution equilibria

recrystallization-solidsolution-equilibria

Recrystallization for Purifying Solid Compounds

Recrystallization is a way to purify solid compounds by using differences in solubility. It does not involve a chemical reaction. Instead, it relies on physical properties of the desired compound and the impurities. The process is based on solid-solution equilibrium, also called solubility equilibrium. In this equilibrium, a component is split between the solid phase and the solution phase. At equilibrium, the chemical potential of that component is the same in both phases. To begin...

crystal growth: principles of crystallization

crystal-growth-principles-of-crystallization

Crystal Formation Through Supersaturation

Crystal formation through supersaturation begins when a solution contains more dissolved solute than it can normally hold. In crystallization, atoms or molecules line up into a rigid crystal lattice so the system can lower its energy. To start the process, the solute concentration and the solution temperature must be adjusted so the supersaturation ratio, S, is greater than one. Supersaturation can be increased in two main ways. One method is to concentrate the solution by evaporating the...

precipitation and co-precipitation

Selective Ion Separation by Precipitation

Selective ion separation by precipitation is used to isolate ions from a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent can be separated by using differences in their solubility products. A solubility product is the limit at which an ionic solid begins to form from dissolved ions. One example is the separation of Cu(II) and Fe(II) ions as insoluble sulfides. Copper(II) sulfide is first precipitated by adding acidic H2S. The acid...

coagulation

Wastewater Cleanup by Coagulation

Coagulation helps remove colloidal particles from wastewater. Colloids are tiny solid particles suspended in a liquid. They are usually negatively charged, so they attract a compact first layer of positive ions. More counterions gather around them and form an electrical double layer. This charge barrier keeps the particles apart and stabilizes the colloid. These suspended solids can be a problem because they may contain toxins that are hard to remove. Coagulation is used to make the particles...

electrodeposition

Electrodeposition for Metal Ion Separation

Electrodeposition separates metal ions from a solution by using an electric current and an electrolytic cell. The cell has an anode and a cathode. When current flows, oxidation happens at the anode. At the cathode, metal ions gain electrons, undergo reduction, and deposit on the large metal surface. This method works well when metals have very different reduction potentials. Copper and nickel in the same solution can be separated this way. First, the solution is made acidic. Then current is...

extraction: partition and distribution coefficients

Solvent partitioning in chemical extraction describes how a solute spreads between two immiscible solvents. Immiscible solvents do not mix, such as an aqueous phase and an organic phase. The distribution law, also called Nernst's distribution law or the partition law, explains how that solute is shared at a constant temperature and equilibrium. At equilibrium, the ratio of solute concentrations in the two solvents stays constant. For extraction from water into an organic solvent, this...

extraction: effects of ph

pH Control in Liquid Extraction

pH control in liquid extraction changes how amines and acids move between organic and aqueous phases. The pH of the aqueous phase affects the charge on acidic and basic solutes. The charged form is usually more soluble in the aqueous phase. For a weak base such as an amine, the neutral form is called B. Its partition coefficient, K, describes how the neutral molecule distributes between the two liquids. If the conjugate acid of the amine is soluble only in the aqueous phase, while the base...

extraction: advanced methods

Chelate Extraction for Metal Ion Separation

Chelate extraction is a way to separate metal ions by using an organic ligand, or chelating agent, to form an uncharged metal complex. The chelating agent needs hydrophobic groups, and it must act as a weak acid so it can lose a proton and bind to the metal. Most organic ligands used for this method are not stable in water or are insoluble in the aqueous phase. For that reason, the chelating agent is first placed in the organic phase. It then moves into the aqueous phase, where the...

chromatography: introduction

Chromatography: Separation by Polarity

Chromatography separates compounds by how they divide between a stationary phase and a mobile phase. The stationary phase is the material that holds the compounds for a time. The mobile phase is the solvent that carries the solutes to be analyzed. In column chromatography, a mixture flows through the stationary phase. The compounds separate based on their structure and polarity. Solutes that interact weakly with the stationary phase move faster through the column and exit first. Solutes that...

dialysis

Dialysis Separation by Diffusion

Dialysis separates small molecules from larger ones by diffusion through a semipermeable membrane. It is a purification method used to remove unwanted ions or small organic molecules from a sample while keeping larger analytes in place. The membrane is usually made of cellulose acetate or cellulose nitrate. Its pores are typically about 1 to 5 nm wide. Molecules such as chloride, sodium, and glucose can pass through these pores. Larger molecules, including proteins, hormones, and enzymes, are...

volatilization

Mass Loss in Gravimetric Analysis

Volatilization gravimetry is a way to measure mass loss in a sample by driving off a volatile substance. It helps estimate how much volatile material is present. In this method, a known amount of sample is heated to a high temperature in a crucible or another suitable vessel. As the sample heats, the volatile substance evaporates. The vapor is then completely removed from the crucible, either by continued heating or by bubbling an inert gas through the vessel. The non-volatile part stays...

ion exchange

Ion Exchange Resins and Charged Molecules

Ion exchange chromatography separates charged molecules from a solution by swapping them with mobile, or active, ions on a stationary phase. It is used to separate ions, soften and deionize water, and purify solutions. The method depends on a solid column made of high-molecular-weight, chemically stable polymers that are crosslinked to make them porous and essentially insoluble. These polymers are functionalized with either acidic or basic groups. When acidic groups are present, the resin is a...

key terms and concepts

Learn how partition and distribution coefficients describe solute movement between immiscible solvents and why they matter in extraction and chromatography.

Solvent Partitioning in Chemical Extraction | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

formula-mass-and-mole-concepts-of-compounds

Formula Mass and Mole Concepts of Compounds

Formula Mass of Covalent Compounds

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Determining the Mass Percent Composition in an Aqueous Solution

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Stoichiometry, Product Yield, and Limiting Reactants

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...

Understand and be prepared to use values specific to chemical processes: the mole, molar mass, molarity, and percent composition. EXPLANATION: During the early and mid-1800s, a tremendous amount of early research poured into building an understanding of the way that atoms combine. This work required analysis of the percent composition of different substances. Joseph Proust's work with tin oxides led him to publish his law of definite proportions noting that a given pure substance will have a constant ratio for the combination of elements making up the substance. Building on Proust's work, John Dalton published his law of multiple proportions and atomic theory noting that multiple patterns exist for the way that atoms combine, yet the combining atoms are invariable. Meanwhile Amedeo Avogadro hypothesizes that given equal pressures and temperatures, two equal volumes of gas will contain equal numbers of atoms. Acknowledging that the exact number of atoms was unknown in these gaseous volumes, the Latin word "mole" was used. "Mole" translates to "lump" recognizing the ambiguous quantity of gas. A number of attempts have been undertaken historically to quantify the mole. Robert Millikan's oil drop experiment revealed the change of a single electron, which could then be divided into Faraday's Constant for the charge of a mole of electrons. Dividing the charge of a mole of electrons by the charge of a single electron yields the number of electrons in a mole, $6.022\times10^{\wedge}23$. Students should be familiar with how to translate between the given quantities. Student's first use atomism/Dalton's atomic theory in third grade noting that matter is made up of particles too small to be seen. This the first time where students will undertake the process of counting these invisible particles. Electrolysis of water provides a tangible experience to demonstrate the constituent parts of water, though the definite proportions of water may not be easily seen due to the solubility of the gasses produced. The concept of relative mass can be explored by comparing small groups of like items. For example, relative masses of beans can be compared with pinto, white, and black beans. If bags are created with equal numbers of like beans, students can develop a concept of why the smallest bean will have a relative mass of 1, analogous to hydrogen.

CHEM1.PS1.1

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Demonstrate that atoms, and therefore mass, are conserved during a chemical reaction by balancing chemical reactions. EXPLANATION: Standard 7.PS1.4 explores the idea that chemical reactions are rearrangements of atoms, and students undertake the process of balancing chemical reactions with that standard in seventh grade. The introduction of molar masses in high school makes an explicit connection between the number of atoms, as previously investigated, and the actual masses of the atoms, permitting the collection of more concrete evidence for the conservation of mass in chemical reactions.

CHEM1.PS1.2

Reaction Yield

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Limiting Reactant

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Chemical Equilibria: Systematic Approach to Equilibrium Calculations

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Perform stoichiometric calculations involving the following relationships: mole- mole; mass-mass; mole-mass; mole- particle; and mass- particle. Show a qualitative understanding of the phenomenon of percent yield, limiting, and excess reagents in a chemical reaction through pictorial and conceptual examples. (states of matter liquid and solid; excluding volume of gasses). EXPLANATION: This standard builds on the idea that balancing chemical reactions provides evidence for conservation of mass and that the behavior of atoms follows predictable patterns. Students now have the opportunity to utilize this understanding as they perform and evaluate chemical reactions. (The concepts of limiting reagent and percent yield are presented; however, students are not expected to determine these values algebraically. Use of molar volume in stoichiometric processes is beyond the scope of this standard.)

CHEM1.PS1.3

Predicting Reaction Outcomes

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Introduction to Chemical Reactions

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Chemical Reactions in Aqueous Solutions

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Precipitation Reactions

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Oxidation-Reduction Reactions

Oxidation&ndash;Reduction Reactions

Earth&rsquo;s atmosphere contains about 20% molecular oxygen, O2, a chemically reactive gas that plays an essential ...

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Acids, Bases and Neutralization Reactions

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to ...

Synthesis and Decomposition Reactions

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Types of Chemical Reactions: Exchange and Reversible

An exchange reaction is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical ...

Use the reactants in a chemical reaction to predict the products and identify reaction classes (synthesis, decomposition, combustion, single replacement, double replacement). EXPLANATION: Chemical reactions are rearrangements of atoms that follow predicable patterns. There are patterns both at the macroscopic level in the behavior of some of the reaction classes, as well as patterns in the rearrangements of the atoms underlying the reaction. Students should be able to predict the products of the reactions, which also requires the ability to recognize the general patterns for each type of reaction.

CHEM1.PS1.4

kinetic-molecular-theory-gas-laws-explain-properties-gas

Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

The test of the kinetic molecular theory (KMT) and its postulates is its ability to explain and describe the behavior of a gas. The various gas laws ...

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Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision

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Ideal Gas Law

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Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law

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Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

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Applications of the Ideal Gas Law: Molar Mass, Density, and Volume

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Conduct investigations to explore and characterize the behavior of gasses (pressure, volume, and temperature), develop models to represent this behavior, and construct arguments to explain this behavior. Evaluate the relationship (qualitative and quantitatively) at STP between pressure and volume (Boyle's Law), temperature and volume (Charles' Law), temperature and pressure (Gay-Lussac Law) and moles and volume (Avogadro's Law), and evaluate and explain these relationships with respect to kinetic molecular theory. Be able to understand, establish, and predict the relationships between volume, temperature, and pressure using combined gas law both qualitatively and quantitatively. EXPLANATION: When exploring the behavior of gasses, it is important to consider experimental design. Experiments used to show the relationships between these sets of variables should include one independent and one dependent variable. Other variables should be held constant. Pressure should serve as the dependent variable because it cannot be manipulated directly. Avogadro's Law can be used to relate the amount of gas in two different containers in lieu of knowing actual number of gas particles in an individual container. Individual demonstrations can be performed to explore each of the different gas laws.

CHEM1.PS1.5

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Use the ideal gas law, PV = nRT, to algebraically evaluate the relationship among the number of moles, volume, pressure, and temperature for ideal gases. EXPLANATION: If students have collected data during investigations for CHEM1.PS1.5, these data can then be used to linearize. With pressure assigned as the dependent variable and plotted against (moles) (temperature)/volume, the slope of the graph will be the gas constant, yielding the ideal gas law. After developing the mathematical model, this model can be used to make predictions for other systems.

CHEM1.PS1.6

Separation of Mixtures via Precipitation

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Filtration

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Centrifugation

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...

Sublimation

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Electrodeposition

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Analyze solutions to identify solutes and solvents, quantitatively analyze concentrations (molarity, percent composition, and ppm), and perform separation methods such as evaporation, distillation, and/or chromatography and show conceptual understanding of distillation. Construct argument to justify the use of certain separation methods under different conditions. EXPLANATION: In seventh grade, students developed an understanding that chemical and physical properties of a sample of matter could be used to identify a substance. Building on this understanding, students now explore the use of these physical and chemical properties to separate mixtures. Analysis of the substances is performed to aid in further discussion and facilitate further quantitative analysis.

Solvent Partitioning in Chemical Extraction

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