Name: raoult's law and lower vapor pressure
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 3 min 28 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

Matter and Its Interactions

CHEM1.PS1.15

Vapor Pressure Lowering

Some properties of a solution depend on the type of solute. An aqueous solution of hydrochloric acid turns a pH paper red, while a sodium hydroxide solution turns it blue.
Other properties of a solution depend only on the concentration or the number of particles of the solute rather than the type of solute. These are called colligative properties.
One such property is the vapor pressure of a solution. The vapor pressure of a liquid is the pressure of the gas above the liquid resulting from evaporation when the liquid and the gas are in a dynamic equilibrium in a closed container.
The vapor pressure of the solution is always less than that of the pure solvent.
Consider a solution made when a non-volatile solute, that is one with no measurable vapor pressure, is added to a volatile solvent.
In a pure solvent, the entire surface of the liquid is solvent particles. Some of these particles escape into the gaseous state to create vapor, while some of the gas molecules above condense back into a liquid state.
When the rate of vaporization equals the rate of condensation, a dynamic equilibrium is reached.
In a solution, the liquid surface has both solute and solvent particles. So, a smalle

vapor pressure lowering

The equilibrium vapor pressure of a liquid is the pressure exerted by its gaseous phase when vaporization and condensation are occurring at equal rates: <img alt="Chemical equation diagram: 2H&#8322; + O&#8322; &#8594; 2H&#8322;O, illustrating water formation from hydrogen, oxygen." src="/files/ftp_upload/11367/11367_Equation_1.png" style="height: 50px;" data-altupdatedat="1761830439000" data-alt="Eq1" />Dissolving a nonvolatile substance in volatile liquid results in a lowering of the liquid&#8217;s vapor pressure. This phenomenon can be explained by considering the effect of added solute molecules on the liquid's vaporization and condensation processes. To vaporize, solvent molecules must be present at the surface of the solution. The presence of solute decreases the surface area available to solvent molecules and thereby reduces the rate of solvent vaporization. Since the rate of condensation is unaffected by the presence of solute, the net result is that the vaporization-condensation equilibrium is achieved with fewer solvent molecules in the vapor phase (i.e., at a lower vapor pressure).While this interpretation is useful, it does not account for several important aspects of the colligative nature of vapor pressure lowering. A more rigorous explanation involves the property of entropy. For purposes of understanding the lowering of a liquid's vapor pressure, it is adequate to note that the more dispersed nature of matter in a solution, compared to separate solvent and solute phases, serves to effectively stabilize the solvent molecules and hinder their vaporization. A lower vapor pressure results, and a correspondingly higher boiling point.The relationship between the vapor pressures of solution components and the concentrations of those components is described by Raoult&#8217;s law: The partial pressure exerted by any component of an ideal solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the solution. <img alt="Chemical equilibrium; equation K = [Products]/[Reactants]; reaction diagram; equilibrium concept." src="/files/ftp_upload/11367/11367_Equation_2.png" style="height: 50px;" data-altupdatedat="1761830439000" data-alt="Eq2" />where PA is the partial pressure exerted by component A in the solution, P&#186;A is the vapor pressure of pure A, and XA is the mole fraction of A in the solution.Recalling that the total pressure of a gaseous mixture is equal to the sum of partial pressures for all its components (Dalton&#8217;s law of partial pressures), the total vapor pressure exerted by a solution containing i components is <img alt="Genetic code chart for amino acid translation, diagram, essential for protein synthesis understanding." src="/files/ftp_upload/11367/11367_Equation_3.png" style="height: 50px;" data-altupdatedat="1761830439000" data-alt="Eq3" />A nonvolatile substance is one whose vapor pressure is negligible (P&#186; &#8776; 0), and so the vapor pressure above a solution containing only nonvolatile solutes is due only to the solvent: <img alt="Chromatography diagram; sample injection, separation columns, detector output flowchart; analysis." src="/files/ftp_upload/11367/11367_Equation_4.png" style="height: 50px;" data-altupdatedat="1761830439000" data-alt="Eq4" />This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/11-4-colligative-properties?query=vapor%20pressure&#38;target={">Openstax, Chemistry 2e, Section 11.4: Colligative Properties.</a>

The equilibrium vapor pressure of a liquid is the pressure exerted by its gaseous phase when vaporization and condensation are occurring at equal rates:
...

Education

JoVE Core

Solutions and Colloids

KEY TERMS AND CONCEPTS

raoult's law and lower vapor pressure

Raoult’s law explains why a solution with a nonvolatile solute has a lower vapor pressure than the pure liquid. Vapor pressure is the pressure from a liquid’s gas phase when vaporization and condensation happen at equal rates. When a nonvolatile substance dissolves in a volatile liquid, the liquid’s equilibrium vapor pressure drops.

One reason for this drop is at the surface of the solution. Solvent molecules must be at the surface to vaporize, and added solute molecules reduce the surface area available to them. As a result, solvent vaporization slows down. The rate of condensation does not change, so equilibrium is reached with fewer solvent molecules in the gas phase.

A more complete explanation uses entropy, which describes how spread out matter is. In a solution, matter is more dispersed than in separate solvent and solute phases. That dispersed arrangement helps stabilize the solvent molecules and makes it harder for them to escape into the vapor. The lower vapor pressure also leads to a higher boiling point.

Raoult’s law links vapor pressure to concentration. For an ideal solution, the partial pressure of a component equals the vapor pressure of the pure component multiplied by its mole fraction in the solution. In a mixture, the total pressure equals the sum of the partial pressures, which follows Dalton’s law of partial pressures. A nonvolatile substance has a vapor pressure that is nearly zero, so the vapor pressure above a solution with only nonvolatile solutes comes from the solvent alone.

Raoult's Law and Lower Vapor Pressure

solution formation

Why Some Substances Dissolve Better

Some substances dissolve easily in one solvent but not in another. A quick way to predict solubility is the idea that "like dissolves like." Polar substances, such as salt and sugar, dissolve well in polar solvents like water. Non-polar substances are more soluble in non-polar solvents such as carbon tetrachloride. This selective solubility depends on intermolecular forces, which are the attractions within and between molecules. Stronger forces between solute and solvent molecules lead to...

intermolecular forces in solutions

How Solutions Form Without Energy Change

A solution can form as a spontaneous process. That means it happens under the right conditions without energy from an outside source. When the attraction between solute and solvent particles is about the same as the attraction in the separate substances, the solution forms with no energy change. A solution like this is called an ideal solution. Mixtures of ideal gases are one example, and helium and argon behave close to that model. These gases do not have significant intermolecular...

enthalpy of solution

Dissolution and Heat Changes

Dissolution and heat changes help explain why some solutions form on their own. Two factors can favor the spontaneous formation of a solution. One is a decrease in internal energy, which happens in an exothermic change. The other is increased dispersal of matter, which means the solute spreads evenly through the solvent. When a substance dissolves, the internal energy often changes as heat is absorbed or released. This does not happen in every case, but it is common. A solution forms when...

aqueous solutions and heats of hydration

How Water Dissolves Ionic Compounds

Water dissolves ionic compounds because its polar molecules attract ions. This attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. It helps explain why many ionic solids can separate in water and form aqueous solutions. When an ionic compound dissolves, its ions separate and spread out evenly through the solution. Water molecules surround the ions and solvate them, which lowers the strong electrostatic forces between the ions. This separation is a...

solution equilibrium and saturation

Saturation Limits in Solutions

Saturation limits in solutions describe how much solute can dissolve in a solvent under given conditions. As sugar is added to water and stirred, it dissolves at first. More sugar can be added until the solution reaches its natural limit. That limit depends mainly on the relative strengths of three attractions: solute-solute, solute-solvent, and solvent-solvent forces. When no more sugar dissolves, even after long stirring, undissolved sugar stays behind. The concentration of sugar in the...

physical properties affecting solubility

Gas Solubility in Liquids

Gas solubility in liquids depends on the attractive forces between the gas and the liquid. When a gas dissolves, there is no strong solute-solute attraction to break apart first. Gas particles are already far apart, so their internal interactions are negligible. That makes solute-solvent interactions the main energetic factor that controls how much gas can dissolve. Examples show how these interactions matter. Oxygen is about three times more soluble in water than helium because oxygen has...

expressing solution concentration

Measuring Solution Strength

Solution strength can be described with terms like dilute and concentrated, and it can also be measured with several scientific units. A solute is the part of a solution present at a lower amount than the solvent. Different units are useful in different situations, especially in chemistry. Molarity, written as M, is a common unit for concentration. It tells how many moles of solute are in one liter of solution. Because solution volume changes with temperature, molarity can change too when the...

Raoult’s law explains why a solution with a nonvolatile solute has a lower vapor pressure than the pure liquid. Vapor pressure is the pressure from a liquid’s gas phase when vaporization and condensation happen at equal rates. When a nonvolatile substance dissolves in a volatile liquid, the liquid’s equilibrium vapor pressure drops. One reason for this drop is at the surface of the solution. Solvent molecules must be at the surface to vaporize, and added solute molecules reduce the surface...

ideal solutions

Raoult's Law in Real Solutions

Raoult's law describes how vapor pressure changes in a solution. For a solvent, the partial vapor pressure equals the vapor pressure of the pure solvent multiplied by its mole fraction in the solution. This relationship works best for ideal solutions. An ideal solution is one in which solvent-solute attractions are just as strong as solvent-solvent and solute-solute attractions. In that case, both components need about the same amount of energy to escape into the vapor phase as they do in...

freezing point depression and boiling point elevation

freezing-point-depression-and-boiling-point-elevation

Colligative Effects in Solutions

Colligative effects in solutions include boiling point elevation and freezing point depression. These properties depend on how many solute particles are present, not on the solute’s chemical identity. Because of that, a solution can behave differently from the pure solvent even when only a nonvolatile solute is added. Boiling point elevation happens because the vapor pressure of a solution is lower than the vapor pressure of the pure solvent. The boiling point is the temperature at which vapor...

osmosis and osmotic pressure of solutions

osmosis-and-osmotic-pressure-of-solutions

Semipermeable Membranes and Reverse Osmosis

Semipermeable membranes let some molecules pass while blocking others. They are found in biological cell membranes and in dialysis tubing used to remove metabolic wastes from blood. These examples show how selective permeation depends on factors such as size, shape, polarity, and charge. Osmosis is the net movement of solvent through a semipermeable membrane. In a U-shaped setup, pure solvent and a solution are separated by a membrane that allows only solvent molecules to pass. Solvent...

electrolytes: van't hoff factor

Electrolyte Ions and the van't Hoff Factor

Electrolyte ions affect colligative properties because these properties depend on the number of dissolved particles, not their identity. The concentration terms used for freezing point depression, boiling point elevation, and osmotic pressure include every solute species present in the solution. Nonelectrolytes dissolve without dissociation, so each molecule that enters solution counts as one particle. Electrolytes behave differently because they can form ions in water. If sodium chloride were...

colloids

Colloids and Everyday Mixtures

Colloids are mixtures with particles between the size of a solution and a suspension. They stay dispersed instead of settling out, even though their particles are larger than most simple molecules. This makes colloids different from cloudy suspensions like mud and water, flour and water, or tempera paint. It also makes them different from solutions, where dissolved molecules or ions are invisible and do not settle. Colloidal systems can be made in two main ways. In dispersion methods, larger...

key terms and concepts

Learn how nonvolatile solutes lower a liquid’s vapor pressure, why the boiling point rises, and how Raoult’s law links pressure to mole fraction.

Raoult's Law and Lower Vapor Pressure | JoVE K12

chemistry

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Virginia  Standards of Learning

HIgh School

CH.5

CH.5.b

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

Formula Mass and Mole Concepts of Compounds

Formula Mass of Covalent Compounds

Chemical formulas represent the elemental makeup of substances. For covalent compounds, the formula represents the ...

Expressing Solution Concentration

A solute is a component of a solution that is typically present at a much lower concentration than the solvent. Solute concentrations are often described ...

determining-the-mass-percent-composition-in-an-aqueous-solution

Determining the Mass Percent Composition in an Aqueous Solution

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Determining the composition of a solution is an important ...

Solutions and Concentrations

Source: Laboratory of Dr. Michael Evans &#8212; Georgia Institute of Technology
A solution is a homogeneous mixture containing some components in small ...

Reaction Stoichiometry

A balanced chemical equation provides a great deal of information in a very succinct format. Chemical formulas provide the identities of the reactants and ...

stoichiometry-product-yield-and-limiting-reactants

Stoichiometry, Product Yield, and Limiting Reactants

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas.
...

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

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

 Balancing Redox Equations

Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or ...

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

The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The ...

A balanced chemical equation provides the information of chemical formulas of the reactants and products involved in the chemical change. A ...

Limiting Reactant

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in ...

chemical-equilibria-systematic-approach-to-equilibrium-calculations

Chemical Equilibria: Systematic Approach to Equilibrium Calculations

In systems with multiple equilibria, the equilibrium calculations use a systematic approach involving a series of steps to make sure there are as many ...

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

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

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

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Oxidation Numbers

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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

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

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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 ...

basic-postulates-kinetic-molecular-theory-particle-size-energy

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

The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For ...

Ideal Gas Law

Derivation of the Ideal Gas Law
Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their ...

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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

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Kinetic Theory of an Ideal Gas

A mole is defined as the amount of any substance that contains as many molecules as there are atoms in exactly 12 grams of carbon-12. An Italian scientist ...

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

The volume occupied by one mole of a substance is its molar volume. The ideal gas law, PV = nRT, &nbsp;suggests that the volume of a given quantity of gas ...

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

Ideal Gas Equation

The ideal gas equation is an equation of state that relates the state variables pressure, volume, temperature, and the number of moles of a hypothetical ...

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
The ideal gas law describes the behavior ...

real-gases-effects-intermolecular-forces-molecular-volume-deriving

Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

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chemical-stoichiometry-gases-using-ideal-gas-law-to-determine

Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles

Chemical stoichiometry describes the quantitative relationships between reactants and products in chemical reactions.

In addition to measuring quantities ...

pV-Diagrams

The pV diagram, which is a graph of pressure versus volume of the gas under study, is helpful in describing certain aspects of the substance. When the ...

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

Source: Laboratory of Dr. Ana J. Garc&#237;a-S&#225;ez &#8212; University of T&#252;bingen
Most samples of interest are mixtures of many different ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

Distillation: Vapor&ndash;Liquid Equilibria

Distillation is a separation technique that takes advantage of the boiling point properties of disparate elements in a mixture. To perform distillation, ...

Filtration

Filtration is the physical separation of solids from a fluid using a filtration medium.
The filtration medium is chosen depending on the purpose of ...

Centrifugation

Centrifugation is a method of separating suspended particles from a liquid by spinning in a centrifuge at a high number of revolutions per minute.
...

Sublimation

Sublimation is the direct phase transformation from the solid to the gaseous phase, bypassing the liquid state.
For example, solid carbon dioxide, or dry ...

recrystallization-solidsolution-equilibria

Recrystallization: Solid&ndash;Solution Equilibria

Recrystallization is a purification technique used to separate impurities from solid compounds. In this technique, no chemical reactions occur. Instead, ...

Precipitation and Co-precipitation

Precipitation and coprecipitation techniques can be applied to separate a mixture of ions.
When different ions form sparingly soluble salts with the same ...

Electrodeposition

During electrodeposition, ions are separated from a solution by deposition on an electrode in an electrolytic cell.
While reduction occurs at the cathode ...

extraction-partition-and-distribution-coefficients

Extraction: Partition and Distribution Coefficients

The distribution law or Nernst&#39;s distribution law is the law that governs the distribution of a solute between two immiscible solvents. This law, also ...

Extraction: Effects of pH

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While organic bases are usually more ...

Extraction: Advanced Methods

Metal ions can be separated by complexation with organic ligands to form uncharged chelates.
The chelating agent must contain hydrophobic groups and ...

Chromatography: Introduction

Chromatography is a technique used to separate compounds based on differences of partitioning between two phases, the stationary phase and the mobile ...

Dialysis

Dialysis separates desired analyte ions or molecules from unwanted molecules, or &#39;interferents&#39;, by allowing the sample solution to diffuse ...

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.

CHEM1.PS1.7

Acids and bases play several important roles in biology. The pH of a biological system can significantly impact the function of biological molecules, ...

Bronsted-Lowry Acids and Bases

The acid-base reaction class has been studied for quite some time. In 1680, Robert Boyle reported traits of acid solutions that included their ability to ...

Lewis Acids and Bases

In 1923, G. N. Lewis proposed a generalized definition of acid-base behavior in which acids and bases are identified by their ability to accept or to ...

acidbase-strengths-and-dissociation-constants

Acid/Base Strengths and Dissociation Constants

The relative strength of an acid or base is the extent to which it ionizes when dissolved in water. If the ionization reaction is essentially complete, ...

Identify acids and bases as a special class of compounds with a specific set of properties. EXPLANATION: The concept of pH is first introduced in seventh grade as a chemical property of matter. Students should be introduced to multiple explanations of acid and base behavior to permit classification of common substances (e.g. baking soda, ammonia, carbon dioxide) as acids or bases. To further develop discussions of solubility, qualitative discussions of the differences between strong and weak acids are appropriate. (Calculations of pH or ion concentrations are beyond the scope of this standard. Discussions of pOH are beyond the scope of this standard. Conjugate pairs are beyond the scope of this standard.)

CHEM1.PS1.8

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Draw models (qualitative models such as picture or diagrams to demonstrate understanding of radioactive stability and decay.) Understand and differentiate between fission and fusion reactions. Use models (graphs or tables) to explain the concept of half-life and its use in determining the age of materials (such as radiometric dating). EXPLANATION: To build an understanding of nuclear processes, students should attribute the existence of the nucleus and nuclear stability to neutrons and the strong nuclear force. The process of fusion is facilitated when two nuclei are forced near one another to the point where strong nuclear forces exceed repulsive electromagnetic forces. Due the random movements of nucleons, decay processes are also random but can be charted exhibiting consistent patterns. These patterns are useful in radiometric dating on varying scales.

CHEM1.PS1.9

Raoult's Law and Lower Vapor Pressure

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