Chemistry
Mixtures and Solutions
Mixtures are combinations of two or more substances that are not chemically bonded and can be separated by physical means. Solutions are homogeneous mixtures where one substance (the solute) is dissolved in another substance (the solvent). Solutions can be liquid, solid, or gas and are commonly found in everyday life, such as saltwater or air.
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12 Key excerpts on "Mixtures and Solutions"
eBook - ePub- Barron's Educational Series, Loris Chen(Authors)
- 2020(Publication Date)
- Barrons Educational Services(Publisher)
Chapter 5 Mixtures MixturesMixtures are two or more substances that have been combined in such a way that they retain their individual chemical characteristics. Substances in a mixture can be separated by ordinary mechanical means using physical properties such as magnetism, density, mass, and particle size. Processes such as boiling, evaporation, and condensation can also be used to separate substances in a mixture.Figure 5–1. Homogeneous vs. heterogeneousIf the substances are so well mixed they appear to be a single substance, they are said to be homogeneous. If the substances appear to be separate components, they form a heterogeneous mixture.Solutions are homogeneous mixtures. In solutions the substance that is in the highest concentration is the solvent. The minority substances are solutes. The solvent dissolves the solutes.When a solid or gas substance dissolves, it is said to be soluble. If a solid or gas substance does not dissolve, it is said to be insoluble.If two liquids completely mix into a solution, they are miscible. If two liquids do not mix completely into a solution, they are immiscible.Examples of mixturesSolvent Solute Example Appearance Gas Gas Nitrogen, oxygen, argon, and other gases in dry air Homogeneous Gas Liquid Fog—liquid water in gases of air Homogeneous Gas Solid Microscopic particulate matter mixed in air Homogeneous Liquid Gas Oxygen dissolved in water Homogeneous Liquid Liquid Vinegar and waterOil and water HomogeneousHeterogeneous Liquid Solid Salt mixed in waterPepper mixed in oil HomogeneousHeterogeneous Solid Gas Oxygen trapped in ice Heterogeneous Solid Solid Particles of rocks mixed as sandMetal alloys such as bronze (copper and tin) HeterogeneousHomogeneous Solid Liquid Silver and mercury in dental fillings Homogeneous PAINLESS TIPThe solvent pulls the solute into solution.
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
(Section 7.3) 4 Calculate solution concentrations in units of molarity, weight/weight percent, weight/volume percent, and volume/ volume percent. (Section 7.4) Elnur/Shutterstock.com Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Solutions and Colloids 199 EARLIER, homogeneous matter was classified into two categories—pure substances and mixtures (see Figure 1.8). Since then, the discussion has been limited to pure substances. We now look at homogeneous mixtures called solutions and their distant relatives, colloidal suspensions. Solutions and colloidal suspensions are very important in our world. They bring nutrients to the cells of our bodies and carry away waste products. The ocean is a solution of water, sodium chloride, and many other substances (even gold). Many chemical reactions take place in solution—including most of those discussed in this book. 7.1 Physical States of Solutions Learning Objective 1 Classify mixtures as solutions or nonsolutions based on their appearance. Solutions are homogeneous mixtures of two or more substances in which the components are present as atoms, molecules, or ions. These uniformly distributed particles are too small to reflect light, and as a result liquid solutions are transparent (clear); light passes through them. In addition, some solutions are colored. The component particles are in constant motion (remember the kinetic theory, Section 6.2) and do not settle under the influence of gravity. In most solutions, a larger amount of one substance is present compared to the other components.
eBook - ePubGeneral Physics
Mechanics and Molecular Physics
- L D Landau, A. I. Akhiezer, E.M. Lifshitz(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
CHAPTER XSOLUTIONS
Publisher Summary
Solutions are mixtures of two or more substances in which the substances are mixed on the molecular scale. The relative amounts of the various substances in the mixture may vary over a more or less wide range. If one substance is present in greater quantity than the others, it is called the solvent and the other substances are called solutes. The composition of a solution is described by its concentration that gives the relation between the quantities of the substances in the mixture —the components of the mixture as they are called. The concentration can be defined in various ways. Physically, the most informative is the molar concentration, that is, the ratio of the numbers of molecules or the ratio of the quantities expressed in moles. Alternatively, one may use concentrations by weight, volume, and so on. The mutual solubility of two substances usually has definite limits; no more than a certain amount of solute can dissolve in a given quantity of solvent. A solution containing the maximum possible quantity of solute is said to be saturated. If further solute is added to such a solution, it will not dissolve. Therefore, it can be said that a saturated solution is one that is in thermal equilibrium with the pure solute. The concentration of the saturated solution is a measure of the ability of a given substance to dissolve in the solvent concerned and is simply called the solubility of the substance. The solubility in general depends on the temperature.§77. Solubility
Solutions are mixtures of two or more substances in which the substances are mixed on the molecular scale. The relative amounts of the various substances in the mixture may vary over a more or less wide range. If one substance is present in greater quantity than the others, it is called the solvent , and the other substances are called solutes
- Frederick Bettelheim, William Brown, Mary Campbell, Shawn Farrell(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
168 Solutions and Colloids 6 CONTENTS 6.1 Introduction to Mixtures 6.2 The Most Common Types of Solutions 6.3 The Distinguishing Characteristics of Solutions 6.4 Factors Affecting Solubility 6.5 The Most Common Units for Concentration 6.6 Water as a Good Solvent 6.7 Colloids 6.8 Colligative Properties 6.1 Introduction to Mixtures In Chapter 2, we discussed pure substances—compounds made of two or more elements in a fixed ratio. Such systems are the easiest to study, so it was convenient to begin with them. In our daily lives, however, we more fre-quently encounter mixtures—systems consisting of more than one compo-nent. Air, smoke, seawater, milk, blood, and rocks, for example, are mixtures (Section 2.2C). Recall that the molecular level is the aspect at which the interactions be-tween molecules becomes significant. If a mixture is uniform throughout at the molecular level, it is called a homogeneous mixture or, more commonly, a solution. Filtered air and seawater, for example, are both solutions. They are clear and transparent. In contrast, in most rocks we can see distinct re-gions separated from each other by well-defined boundaries. Such rocks are heterogeneous mixtures. Another example is a mixture of sand and sugar. We can easily distinguish between the two components; the mixing does not occur at the molecular level (Figure 2.3). Thus, mixtures are classified on the basis of how they look to the unaided eye. Some systems, however, fall between homogeneous and heterogeneous mixtures. Cigarette smoke, milk, and blood plasma may look homogeneous, but they do not have the transparency of air or seawater. These mixtures are classified as suspensions. We will deal with such systems in Section 6.7. Although mixtures can contain many components, we will generally re-strict our discussion to two-component systems, with the understanding that everything we say can be extended to multicomponent systems.
eBook - ePub- Britannica Educational Publishing, Erik Gregersen(Authors)
- 2010(Publication Date)
- Britannica Educational Publishing(Publisher)
CHAPTER 5 LIQUID SOLUTIONS AND SOLUBILITYT he ability of liquids to dissolve solids, other liquids, or gases has long been recognized as one of the fundamental phenomena of nature encountered in daily life. The practical importance of solutions and the need to understand their properties have challenged numerous writers since the Ionian philosophers and Aristotle. Many physicists and chemists have devoted themselves to a study of solutions.A solution is a mixture of two or more chemically distinct substances that is said to be homogeneous on the molecular scale—the composition at any one point in the mixture is the same as that at any other point. This is in contrast to a suspension (or slurry), in which small discontinuous particles are surrounded by a continuous fluid. Although the word solution is commonly applied to the liquid state of matter, solutions of solids and gases are also possible. Brass, for example, is a solution of copper and zinc, and air is a solution primarily of oxygen and nitrogen with a few other gases present in relatively small amounts.The ability of one substance to dissolve another depends always on the chemical nature of the substances, frequently on the temperature, and occasionally on the pressure. Water, for example, readily dissolves methyl alcohol but does not dissolve mercury; it barely dissolves benzene at room temperature but does so increasingly as the temperature rises. While the solubility in water of the gases present in air is extremely small at atmospheric pressure, it becomes appreciable at high pressures where, in many cases, the solubility of a gas is (approximately) proportional to its pressure. Thus, a diver breathes air (four-fifths nitrogen) at a pressure corresponding to the pressure around him, and, as he goes deeper, more air dissolves in his blood. If he ascends rapidly, the solubility of the gases decreases so that they leave his blood suddenly, forming bubbles in the blood vessels. This condition (known as the bends) is extremely painful and may cause death; it can be alleviated by breathing, instead of air, a mixture of helium and oxygen because the solubility of helium in blood is much lower than that of nitrogen.
eBook - ePubLiquid-State Physical Chemistry
Fundamentals, Modeling, and Applications
- Gijsbertus de With(Author)
- 2013(Publication Date)
- Wiley-VCH(Publisher)
11 Mixing Liquids: Molecular SolutionsSo far, we have discussed pure liquids with increasing complexity. In this chapter we start with solutions and, in particular, with molecular solutions. We first deal briefly with some basic aspects, including molar and partial quantities, perfect, and ideal solutions. Thereafter, nonideal behavior is discussed, based on a treatment of the regular solution model. Finally, some possible improvements are indicated.11.1 Basic Aspects
In this section we iterate and extend somewhat on some of the basic aspects that were introduced in Chapter 2 . The content of a system is defined by the amount of moles nα of chemical species α in the system, often denoted as components, which can be varied independently. A mixture is a system with more than one component. A homogeneous part of a mixture, that is, with uniform properties, is addressed as a phase, while a multicomponent phase is labeled a solution. The majority component of a solution is the solvent, while solute refers to the minority component. We restrict ourselves from the outset to binary Mixtures and Solutions and use, apart from nα for the number of moles, Nα for the number of molecules and xα for the mole fraction of component α. The label 1 refers always to the solvent (e.g., x1 or 1 − x), while the label 2 indicates the solute (e.g., x2 or x). As usual, NA denotes Avogadro's constant.11.1.1 Partial and Molar Quantities
We refer for an arbitrary extensive quantity Z of a mixture to molar quantities Zm defined by Zm = Z/Σα nα or for single, pure component α by . For solutions, it is also useful to discuss the situation with respect to extensive quantities Z in terms of partial (molar) quantities Zα ≡ (∂Z/∂nα )P,T,n′, where n′ indicates all components except for the component α. Generally, for Z = Z(P,T,nα
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
Steve Cole/Exactostock/SuperStock M ost substances we encounter in our daily lives are mixtures. Often they are homogeneous mixtures, which are called solutions. Some so- lutions we commonly encounter are shampoo, soft drinks, and wine. Blood plasma is a complex mixture composed of compounds and ions dissolved in water and proteins suspended in the solution. These solutions all have water as a main component, but many common items, such as air, gasoline, and steel, are also solutions that do not contain water. Brass, a solid solution of zinc and copper, is used to make musical instru- ments like the trumpet in the photo above. What are the necessary components of a solution? Why do some substances dissolve, while others do not? What effect does a dissolved substance have on the properties of the solution? Answering these questions is the first step in understanding the solutions we encounter in our daily lives. Solutions C H A P T E R O U T L I N E 14.1 General Properties of Solutions 14.2 Solubility 14.3 Rate of Dissolving Solids 14.4 Concentration of Solutions 14.5 Colligative Properties of Solutions 14.6 Osmosis and Osmotic Pressure 14 14.1 • General Properties of Solutions 313 14.1 General Properties of Solutions List the properties of a true solution. The term solution is used in chemistry to describe a system in which one or more sub- stances are homogeneously mixed or dissolved in another substance. A simple solution has two components: a solute and a solvent. The solute is the component that is dissolved or is the least abundant component in the solution. The solvent is the dissolving agent or the most abundant component in the solution. For example, when salt is dissolved in water to form a solution, salt is the solute and water is the solvent. Complex solutions containing more than one solute and/or more than one solvent are common.
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Photodisc M ost substances we encounter in our daily lives are mixtures. Often they are homogeneous mixtures, which are called solutions. Some solutions we commonly encounter are shampoo, soft drinks, and wine. Blood plasma is a complex mixture composed of compounds and ions dissolved in water and proteins suspended in the solution. These solutions all have water as a main component, but many common items, such as air, gasoline, and steel, are also solutions that do not contain water. What are the neces- sary components of a solution? Why do some substances dissolve, while others do not? What effect does a dissolved substance have on the properties of the solution? Answering these questions is the first step in understanding the solutions we encounter in our daily lives. 14.1 General Properties of Solutions 14.2 Solubility 14.3 Rate of Dissolving Solids 14.4 Concentration of Solutions 14.5 Colligative Properties of Solutions 14.6 Osmosis and Osmotic Pressure SOLUTIONS C H A P T E R 14 Brass, a solid solution of zinc and copper, is used to make musical instruments and many other objects. C H A P T E R O U T L I N E 306 CHAPTER 14 • Solutions 14.1 GENERAL PROPERTIES OF SOLUTIONS List the properties of a true solution. The term solution is used in chemistry to describe a system in which one or more substances are homogeneously mixed or dissolved in another substance. A simple solution has two com- ponents: a solute and a solvent. The solute is the component that is dissolved or is the least abundant component in the solution. The solvent is the dissolving agent or the most abundant component in the solution. For example, when salt is dissolved in water to form a solution, salt is the solute and water is the solvent. Complex solutions containing more than one solute and/or more than one solvent are common.
eBook - PDF- David A. Ucko(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
The solubility of most solids in water increases with increasing temperature. 13.4 A solution is saturated when it contains the maximum possible amount of dissolved solute under normal conditions at a particular temperature. At this point, the rate at which solute dissolves exactly equals the rate at which solute returns from the solution. 13.5 Liquids that mix completely in any proportion are said to be miscible. Immiscible liquids do not mix. All gases can mix to form solutions. The solubility of a gas in a liquid increases with increasing pressure but decreases with increasing temperature. 13.6 Solvents serve as a medium in which substances react and form products. Solvents are also used as cleaners, to deposit coatings, and in industrial processing. 13.7 The concentration of a solution describes the amount of solute present in any given quantity of solvent or solution. Concentration can be expressed as a percentage based on the ratios of solute and solution in terms of weight to volume, weight to weight, or volume to volume. 13.8 Molarity is defined as the number of moles of solute per liter of solution. Two solutions with the same molarity contain equal numbers of moles of solute per liter. However, they generally contain different masses of solute. 13.9 Solutions are often prepared by diluting a portion of an existing stock solution. Dilution calculations can be made using the relationship Mi x Vi = M 2 x V 2 , or by using the conversion factor method. 13.10 When a reaction takes place in aqueous solution, some of the reactants and products are often present as ions. The net ionic equation expresses the reaction in simplified form. Spectator ions, those that do not participate in the reaction, do not appear in a net ionic equation. 13.11 Colligative properties are properties that depend only on the number of solute particles in a solution. Colligative properties include 440
eBook - PDFBasic Physical Chemistry
The Route to Understanding
- E Brian Smith(Author)
- 2012(Publication Date)
- ICP(Publisher)
10 Mixtures and Solutions Many chemical experiments are carried out in solution and it is therefore very important that we are able to understand the behaviour of substances in solution. The simplest model of a mixture is the ideal solution . Such a solution is formed when the components have molecular interactions which are virtually identical. It is a severe approximation, but it provides the platform from which all real solutions are approached. 10.1 The ideal solution Consider the process where two very similar, but distinct, substances are mixed. The mixing leads to an increase in entropy which arises because, whereas the interchange of molecules in a pure compound does not produce a different microstate, the exchange of molecules in a mixture does. If we assume the components are sufficiently similar to mix randomly, then W mix = (n 1 + n 2 ) ! n 1 ! n 2 ! (see Section 7.4). However, since S = k ln W and Stirling’s approximation, when N is large, gives ln N ! = N ln N − N , we obtain, for the entropy arising from the mixing process, mix S = k [ (n 1 + n 2 ) ln (n 1 + n 2 ) − (n 1 + n 2 ) − n 1 ln n 1 − n 2 ln n 2 + n 1 + n 2 ] . This can be rearranged to give, mix S = k (n 1 + n 2 ) − n 1 (n 1 + n 2 ) ln n 1 (n 1 + n 2 ) − n 2 (n 1 + n 2 ) ln n 2 (n 1 + n 2 ) . 231 232 | Basic Physical Chemistry The mole fraction of component one is x 1 = n 1 /(n 1 + n 2 , ) , that of component two is x 2 = n 2 /(n 1 + n 2 ) and ( n 1 + n 2 ) = N , so we obtain mix S = − Nk(x 1 ln x 1 + x 2 ln x 2 ) and, for one mole, when N = N A , mix S = − R(x 1 ln x 1 + x 2 ln x 2 ). x i < 1 and so mix S > 1 and the entropy change on mixing is positive. We assume that, since the molecules making up the mixture are very similar, mix H = 0 . And, since mix G = mix H − T mix S , we obtain, for an ideal solution, mix G = RT (x 1 ln x 1 + x 2 ln x 2 ). mix G < 1 and mixing occurs with a negative free energy change and, therefore, is a spontaneous process.
eBook - PDFChemistry
The Molecular Nature of Matter
- James E. Brady, Neil D. Jespersen, Alison Hyslop(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Lawrence Lawry/Photo Researchers Mixtures at the Molecular Level: Properties of Solutions Chapter Outline 12.1 | Intermolecular Forces and the Formation of Solutions 12.2 | Heats of Solution 12.3 | Solubility as a Function of Temperature 12.4 | Henry’s Law 12.5 | Concentration Units 12.6 | Colligative Properties 12.7 | Heterogeneous Mixtures The value of gemstones lies in their beauty and rarity. However, as chemists, we can think of them as solutions: solid solutions with the solute that gives them their colors. Chromium in aluminum oxide for rubies, chromium in beryllium aluminosilicate for emeralds, iron and titanium in aluminum oxide for sapphires, and copper in copper phosphoaluminate for turquoise—these metals are dissolved in the solids. 12 575 576 Chapter 12 | Mixtures at the Molecular Level: Properties of Solutions I n Chapter 4 we discussed solutions as a medium for carrying out chemical reactions. Our focus at that time was on the kinds of reactions that take place in solution, and in particular, those that occur when water is the solvent. In this chapter we will examine how the addition of a solute affects the physical properties of the mixture. In our daily lives we take advantage of many of these effects. For example, we add ethylene glycol (antifreeze) to the water in a car’s radiator to protect it against freezing and overheating because water has a lower freezing point and higher boiling point when solutes are dissolved in it. Here we will study not only aqueous solutions, but also solutions involving other solvents. We will concentrate on liquid solutions, although solutions can also be gaseous or solid. In fact, all gases mix completely at the molecular level, so the gas mixtures we examined in Chapter 10 were gaseous solutions. Solid solutions, called alloys, include such materials as brass and bronze.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
life. The relative amounts of iron, carbon, nickel, and other elements in steel (a mixture known as an “alloy”) determine its physical strength and resistance to corrosion. The relative amount of the active ingredient in a medicine determines its effectiveness in achieving the desired pharmacological effect. The relative amount of sugar in a beverage determines its sweetness (see Figure 3.14). This section will describe one of the most common ways in which the relative compositions of mixtures may be quantified. FIGURE 3.14 Sugar is one of many components in the complex mixture known as coffee. The amount of sugar in a given amount of coffee is an important determinant of the beverage’s sweetness. (credit: Jane Whitney) Solutions Solutions have previously been defined as homogeneous mixtures, meaning that the composition of the mixture (and therefore its properties) is uniform throughout its entire volume. Solutions occur frequently in nature and have also been implemented in many forms of manmade technology. A more thorough treatment of solution properties is provided in the chapter on solutions and colloids, but provided here is an introduction to some of the basic properties of solutions. The relative amount of a given solution component is known as its concentration. Often, though not always, a solution contains one component with a concentration that is significantly greater than that of all other components. This component is called the solvent and may be viewed as the medium in which the other components are dispersed, or dissolved. Solutions in which water is the solvent are, of course, very common on our planet. A solution in which water is the solvent is called an aqueous solution. 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 with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
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