Name: how solubility depends on free energy
Uploaded: 2023-04-30T18:28:32.000Z
Duration: 2 min 21 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

CHEM1.PS2.3

Chemical and Solubility Equilibria

נזכיר כי היווצרות תמיסה מווסתת על ידי אנטרופיה של ערבוב, ערבוב Δ S. האנרגיה החופשית המשויכת לערבוב, ערבוב ΔG, מבוטאת על ידי החלפת ערבוב ΔS במשוואת האנרגיה החופשית של גיבס.
מכיוון שערבוב ΔS אינו תלוי באינטראקציות בין-מולקולריות, שינויי האנרגיה הקשורים לאינטראקציות אלה מוזנחים, והערך של ערבוב ΔH במשוואה הוא 0. לפיכך, ערבוב ΔG שווה לערבוב T שלילי כפול ΔS.
שינוי האנרגיה החופשית הקשור להמסת מומס בליטר ממס נקרא האנרגיה החופשית של תמיסה, תמיסת ΔG. מבחינה מתמטית, הוא מבוטא כסכום האנרגיה החופשית של ערבוב, ערבוב ΔG, והאנרגיה החופשית של אינטראקציה, אינטראקציה ΔG, בין החלקיקים המרכיבים.
אם יחסי הממס-מומס אינם יכולים להתגבר על אינטראקציות המומס-מומס והממס-ממס, האינטראקציה ΔG גדולה מ-0.
אם אינטראקציית Δ G גדולה מספיק, פתרון ΔG גדול מאפס. ככל שתמיסת ΔG גדלה, כמות המומס שמתמוססת בממס פוחתת.
לעומת זאת, אם אינטראקציית ΔG זניחה, תמיסת ΔG הכוללת שווה לערבוב ΔG, והמומס מתמוסס לחלוטין בממס.
שקול להמיס פנטאן בהקסאן. אטרקציות הקסאן-פנטאן בתמיסה מחליפות חלק מהאטרקציות פנטאן-פנטאן והקסאן-הקסאן בנוזל הטהור. מכיוון ששתי המולקולות הן מאותו סוג, אינטראקציית Δ G קרובה ל-0, ערבוב ΔG שולט, ונוצרת תמיסה.
היווצרות התמיסה תלויה באיזון בין אינטראקציית ΔGוערבוב ΔG. פתרון יכול להיווצר גם אם אינטראקציה ΔG היא חיובית, בתנאי שהיא לא גבוהה מדי.
בקיצור, היווצרות תמיסה היא חיובית אם פתרון ΔG קטן מ-0, ואילו הוא שלילי אם פתרון ΔG גדול מ-0.

שיווי משקל כימי ומכפלת מסיסות

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 שינוי האנרגיה החופשית הקשור להמסת מומס בליטר ממס נקרא האנרגיה החופשית של תמיסה, Δ
 
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 הכולל מתבטא כאיזון של Δ
 
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 מול האנרגיה החופשית המועדפת תמיד של ערבוב, Δ
 
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 mixing
 
 . היווצרות תמיסה מועדפת אם Δ
 
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 קטן מאפס, ואילו Δ
 
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 אינו מועדף אם Δ
 
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 גדול מאפס. בקיצור, כדי שייווצר תמיסה ופירוק מוחלט יתרחש, שינוי האנרגיה של גיבס חייב להיות שלילי. הכמות שאליה מומס מתמוסס בממס נשלטת על ידי עוצמת הכוחות הבין-מולקולריים בין הרכיבים. תכונה זו של פירוק מכונה מסיסות.
 
 
 בנוסף לאנרגיה החופשית של ערבוב, אינטראקציות לא קוולנטיות תורמות גם להיווצרות תמיסה. חומרים היוצרים קשרי מימן נקראים חומרים קוטביים. במקרים כאלה, המשיכה של דיפול-דיפול של חלקיקים מומסים עם חלקיקי ממס היא חזקה כמו זו שבין מולקולות במומס טהור או ממס. לפיכך, שני סוגי המולקולות מתערבבים בקלות. כמו כן, נוזלים לא קוטביים מתערבבים זה עם זה מכיוון שאין הבדל ניכר בחוזקות של משיכה בין מולקולרית של מומס-מומס, ממס-ממס ומומס-ממס. אם לזוג מומס וממסים יש משיכה בין-מולקולרית דומה לזו בנוזל טהור, Δ
 
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 הכולל היא זניחה. Δ
 
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 הכולל שווה ל- Δ
 
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 , והמומס מתמוסס לחלוטין בממס. עם זאת, אם מערבבים שני חומרים שונים באופן משמעותי, ההסתברות להיווצרות תמיסה תלויה באיזון בין Δ
 
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 interaction
 
 ל- Δ
 
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 mixing
 
 . הם יכולים ליצור תמיסה גם אם Δ
 
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שינוי האנרגיה החופשית הקשור להמסת מומס בליטר ממס נקרא האנרגיה החופשית של תמיסה, ΔGsolution. בסך הכל ...

Education

JoVE Core

Organic Chemistry

כימיה אורגנית

Unit 1

יחידה 1

Thermodynamics and Chemical Kinetics

תרמודינמיקה וקינטיקה כימית

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

how solubility depends on free energy

Solubility depends on free energy changes when a solute dissolves in a solvent. The free energy change for this process is called the free energy of solution, ΔGsolution. When ΔGsolution is less than zero, solution formation is favorable. When it is greater than zero, solution formation is unfavorable.

For complete dissolution to happen, the Gibbs energy change must be negative. This means the balance of forces in the mixture must favor solution formation. The amount a solute dissolves in a solvent is called its solubility. It depends on the strength of intermolecular forces between the solute and the solvent.

Non-covalent interactions also help determine whether a solution forms. Polar substances can form hydrogen bonds. In these cases, dipole-dipole attractions between solute particles and solvent particles are about as strong as those in the pure substances, so the two kinds of molecules mix easily. Nonpolar liquids are also miscible with each other because the solute-solute, solvent-solvent, and solute-solvent attractions do not differ much.

When a solute and solvent have intermolecular attractions similar to those in a pure liquid, ΔGinteraction is negligible. Then the overall ΔGsolution equals ΔGmixing, and the solute dissolves completely in the solvent. If two very different substances are mixed, solution formation depends on the balance between ΔGinteraction and the always-favorable ΔGmixing. A solution can still form even when ΔGinteraction is positive, as long as it is not too large.

How Solubility Depends on Free Energy

chemical reactions

Stoichiometry, Rates, and Equilibrium

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entropy and solvation

Hydrophobic Effects in Solvation

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gibbs free energy and thermodynamic favorability

gibbs-free-energy-and-thermodynamic-favorability

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chemical and solubility equilibria

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rate law and reaction order

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effect of temperature change on reaction rate

effect-of-temperature-change-on-reaction-rate

Arrhenius Equation in Reaction Speed

The Arrhenius equation connects activation energy, temperature, and the rate constant, k, for many chemical reactions. It helps explain why some reactions move slowly while others happen faster. In this equation, R is the ideal gas constant, with a value of 8.314 J/mol·K. T is the temperature in kelvin, Ea is the activation energy in joules per mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor, A, describes how often reacting molecules collide and how well...

multi-step reactions

Reaction Mechanisms and Rate-Determining Steps

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bond dissociation energy and activation energy

bond-dissociation-energy-and-activation-energy

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energy diagrams, transition states, and intermediates

energy-diagrams-transition-states-and-intermediates

Reaction Coordinate Diagrams in Chemical Reactions

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predicting reaction outcomes

How Temperature Changes Reaction Rate

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key terms and concepts

Explore how free energy, intermolecular forces, and mixing determine solubility. Learn why some polar and nonpolar substances dissolve more easily than others.

How Solubility Depends on Free Energy | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Minnesota Academic Standards in Science

9-12

3.2.1 9C.3.2.1.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Chemical Bonds


Atoms participate in a chemical bond formation&#160;to acquire a completed valence-shell electron configuration similar to that of the noble gas nearest ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Draw, identify, and contrast graphical representations of chemical bonds (ionic, covalent, and metallic) based on chemical formulas. Construct and communicate explanations to show that atoms combine by transferring or sharing electrons. EXPLANATION: This standard resumes discussions of interactions between atoms from 7.PS1. In seventh grade, students observed patterns within the periodic table that related the physical and chemical properties of substances to the location of the constituent elements on the periodic table. Revisiting general trends is likely to be necessary however a focus should be placed on the transfer of electrons underlying differences in the differences in properties. It is beneficial to show that electrostatic interactions occur even between two non-conductors. Demonstrations can be carried out by using static charge to hold a balloon against a wall or showing that oppositely charged pieces of invisible tape are attracted not only to each other but also to a neutral conductors and non-conductors such as foil strips or paper.

CHEM1.PS2.1

intermolecular-forces-and-physical-properties

Intermolecular Forces and Physical Properties



Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

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Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Understand that intermolecular forces created by unequal distribution of charges result in the varying degrees of attraction between molecules. Compare and contrast the intermolecular forces (hydrogen bonding, dipole-dipole bonding and London dispersion forces) within different types of simple substances (only those following the octet rule) and predict and explain their effect on chemical and physical properties of those substances using models or graphical representations. EXPLANATION: This standard resumes where students left off in 7.PS1. Students' first exposure to all three phases of matter was in third grade, by fifth grade students were investigating phase changes in matter. These discussions have not included a mechanism to explain why states of matter are dependent on temperature and pressure. Students should consider this standard in conjunction with CHEM1.PS2.1 to explore differences in intermolecular attractions within molecular and ionic compounds and the behavior of electrons leading to these differences.

CHEM1.PS2.2

Solution Formation

There is no one solvent that can dissolve every type of solute. Some substances that readily dissolve in a certain solvent might be insoluble in a ...

Energetics of Solution Formation

The formation of a solution is an example of a spontaneous process, which is a process that occurs under specified conditions without energy from some ...

The free energy change associated with dissolving a solute in a liter of solvent is called the free energy of a solution, &#916;Gsolution. The overall ...

Entropy and Solvation

The process of surrounding a solute with solvent is called solvation. It involves evenly distributing the solute within the solvent. The rule of thumb for ...

Solubility Equilibria: Overview

Consider a saturated solution of sparingly soluble salt calcium fluoride with excess solid calcium fluoride. The already dissolved calcium fluoride has ...

Physical Properties Affecting Solubility

Solutions of Gases in Liquids
As for any solution, the solubility of a gas in a liquid is affected by the attractive intermolecular forces between solute ...

solubility-equilibria-ionic-product-of-water

Solubility Equilibria: Ionic Product of Water

Water is a weak electrolyte and undergoes a small amount of self-ionization.
At any given temperature, the concentration of undissociated water is ...

Construct a model to explain the process by which solutes dissolve in solutes, and develop an argument to describe how intermolecular forces affect the solubility of different chemical compounds. EXPLANATION: A similar task and standard exist in the fifth grade (5.PS1.3). At that time, students performed an investigation (which is again mentioned in CHEM1.PS2.4) into factors affecting solubility. However, student background knowledge was not sufficient to explore any explanation of their results. Explorations into intermolecular attractions in the previous standard (CHEM1.PS2.2) have introduced students to the existence of forces between molecules in a substance. Students can now apply these attractions to form explanations for how solute-solute, solute-solvent, and solvent-solvent attractions all interact as substances dissolve. (Solubility constants and saturation of solutions are beyond the scope of this standard.)

Temperature Dependence on Reaction Rate

The Collision Theory
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Predicting Reaction Outcomes

Kinetics describes the rate and path by which a reaction occurs. In contrast, thermodynamics deals with state functions and describes the properties, ...

Conduct an investigation to determine how temperature, surface, and stirring affect the rate of solubility. Construct an argument to explain the relationship observed in experimental data using collision theory. EXPLANATION: This standard is nearly identical to a fifth grade standard which explores factors affecting the solubility of a compound. Though collision theory is more closely related to rates of reaction, in this case the application of collision theory explores how the same factors underlying collision theory for how reactions also facilitate solvation processes.

CHEM1.PS2.4

How Solubility Depends on Free Energy

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