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Chapter

Cover Elements of Physical Chemistry

Solutions  

This chapter examines solutions. Chemistry is concerned with liquid solutions as well as gaseous mixtures, so for thermodynamic discussion of their properties it is necessary to have an expression for the chemical potential of solutes and solvents. The key to setting up an expression for the chemical potential of a solute is the work done by the French chemist François Raoult. Raoult's law states that the partial vapour pressure of a substance in a liquid mixture is proportional to its mole fraction in the mixture and its vapour pressure when pure. An ideal solution is one in which both components obey Raoult's law over the entire composition range. Meanwhile, Henry's law states that the vapour pressure of a volatile solute B is proportional to its mole fraction in a solution. An ideal–dilute solution is one in which the solute obeys Henry's law.

Chapter

Cover Atkins’ Physical Chemistry

The properties of solutions  

This chapter applies the concept of chemical potential to the discussion of the effect of a solute on certain properties of a solution. These properties include the lowering of the vapour pressure of the solvent, the elevation of its boiling point, the depression of its freezing point, and the origin of osmotic pressure. It is possible to construct a model of a certain class of non-ideal solutions called ‘regular solutions’, which have properties that diverge from those of ideal solutions. The chapter then looks at the colligative properties, which all stem from the reduction of the chemical potential of the liquid solvent as a result of the presence of solute. A colligative property depends only on the number of solute particles present, not their identity.

Chapter

Cover Biological Science

Ratio and Proportion  

This chapter focuses on the expression and comparison of ratio and proportion. The ideas of ratio and proportion can be expressed using a variety of symbols. Their notation is often used interchangeably when describing these ideas. A part-to-whole ratio is often expressed as a fraction, especially since a diagram can be a helpful way to visualise ratio. The chapter also considers the notions of probability and the term concentration in relation to the notion that solutions can be expressed as the mass of a substance per volume. It then considers the dilution of a solution which is carried out to make the concentration ten times less.

Chapter

Cover Biological Science

Ratio and Proportion  

This chapter focuses on the expression and comparison of ratio and proportion. The ideas of ratio and proportion can be expressed using a variety of symbols. Their notation is often used interchangeably when describing these ideas. A part-to-whole ratio is often expressed as a fraction, especially since a diagram can be a helpful way to visualise ratio. The chapter also considers the notions of probability and the term concentration in relation to the notion that solutions can be expressed as the mass of a substance per volume. It then considers the dilution of a solution which is carried out to make the concentration ten times less.

Chapter

Cover Organic Chemistry

Acids and Bases  

This chapter begins by outlining definitions of acids and bases based on Johannes N. Brønsted and Gilbert N. Lewis. Substances that taste sour have long been known as acids. Bases, on the other hand, are compounds which counteract or neutralize acids. The chapter then reviews the dissociation of a Brønsted acid in aqueous solution. It also presents the two important properties of buffer solutions. First, they allow us to prepare an aqueous solution of a desired pH using a weak acid and its conjugate base (a salt of the acid). The second important property of a buffer solution is that its pH will remain approximately constant if relatively small amounts of a further acid or base are added. Next, the chapter focuses on the factors which affect acid and base strengths. It also analyzes the basicity of organic compounds and the solvent effects on acid-base reactions.

Chapter

Cover f-Block Chemistry

Coordination chemistry  

This chapter begins by discussing coordination chemistry in aqueous solution, and then moves on to the more varied coordination chemistry that is seen in non-aqueous solution. It covers the complexes of f-elements, excluding those with Ln- or An-carbon bonds. The chapter also highlights the importance of chelating and macrocyclic ligands in f-element coordination chemistry, particularly in aqueous solution. Both lanthanoids and actinoids are generally considered as hard Lewis acids, and so their coordination chemistry is dominated by hard O and N donor ligands. Bonding is highly ionic in most cases, resulting in labile complexes that can have highly irregular coordination geometries dictated by ligand steric factors. Large ionic radii result in high coordination numbers, except where ligands are exceptionally sterically demanding.

Chapter

Cover Physical Chemistry for the Life Sciences

The thermodynamic description of aqueous solutions  

This chapter turns to the thermodynamic description of aqueous solutions. In order to assess the energy requirements of a particular process, it is necessary to develop a framework for assessing the thermodynamic stability of the components in a solution. As a first step, this chapter considers only homogeneous mixtures, or solutions, in which the composition is uniform throughout. The component in smaller abundance is called the ‘solute’ and that in larger abundance is the ‘solvent’. Most of the chapter focuses on aqueous solutions, as these are of great importance in biochemistry, but the concepts transfer with little change to more general systems. Except in one case, the chapter focuses on non-electrolyte solutions, where the solute is not present as ions, for example a solution of glucose in water.

Chapter

Cover Making the Transition to University Chemistry

Acid–base Equilibrium  

This chapter explains the acid-base equilibrium. This involves the transfer of protons in line with the Brønsted–Lowry theory. A strong acid or strong base is fully ionized in an aqueous solution, while weak acids or bases are only partially ionized in an aqueous solution. Acid-base titrations measure the unknown concentration of one solution by reaction with another standard solution with a familiar concentration. The chapter also notes how indicators are typically water-soluble weak organic acids with varying colours at different pH values. It explores the alternative theory of acid-base reactions proposed by Gilbert Lewis: a Lewis acid is an electron-pair acceptor, while a Lewis base is an electron-pair donor.

Chapter

Cover Electrode Potentials

Migration of ions  

This chapter covers fully dissociated electrolytes, which are known as strong electrolytes in contrast with weak electrolytes that are largely undissociated in aqueous solution. It refers to the cations which move to the negative electrodes, while anions move towards the positive electrode in the zone of the solution between the electrodes. It also analyses the movement of the ions which constitutes the flow of current in the bulk of the solution. The chapter probes the nature of the current flow at electrode/solution interfaces. It emphasizes that the conductivity is a property of the chemical nature and composition of the electrolyte which implies that the resistance to current flow increases with greater distance between the electrodes and the smaller electrode area.

Chapter

Cover Chemistry3

Analytical chemistry  

This chapter talks about analytical chemistry, which is concerned with determining which substances are in a sample (qualitative analysis) and how much of each substance is present (quantitative analysis). A great deal of interesting and exciting scientific discovery has gone into advancing analytical chemistry and the chapter brings together a number of topics from across all branches of the subject. The chapter describes the chemical principles behind a range of analytical methods and show how they can be used. It lists some of the methods used in analytical chemistry, such as titrations and gravimetric analysis. It deals with instrumental chemical analysis and shows how this covers a wide range of concentrations. It also shows how to calculate the concentrations of analyte solutions given the appropriate calibration data using calibration curves or the standard addition method as appropriate.

Chapter

Cover Core Maths for the Biosciences

Molarity and dilutions  

This chapter sets out the calculations required to work effectively with materials in solutions. It explains that a solution consists of a certain amount of solid or liquid chemical, called solutes, dissolved in a volume of liquid, called the solvent, which for biological purposes is usually water. It also defines the molar mass of a substance as the mass (in grams) of one mole of the substance, noting that the mass of a substance can help determine the number of moles and molecules present. The chapter points out that, as each molecule is made up of atoms, the mass required for one mole can easily be determined by addition of the masses of the individual atoms that make up the molecule. It discusses the concept of moles, which determines the concentration of solutions in terms of how many moles of a substance are contained in a solution; this is called molarity of the solution.

Book

Cover The Heavier d-Block Metals
The Heavier d-Block Metals addresses the chemistry of the second- and third-row d-block metals. Chapter 1 looks at the metals and summarizes occurrence, physical properties, and uses. Chapter 2 considers periodic trends in properties. Chapter 3 considers aqueous solution chemistry, species present (with comparisons of the first-row metal ions), and redox properties. Chapter 4 surveys structure. Chapter 5 looks at electronic spectra and magnetic properties, making comparisons with the first row the main objective of the chapter. Chapter 6 considers metal-metal bonding, and the classes of compound that contain triple and quadruple bonds, and the role of bridging ligands is introduced. Chapter 7 looks at selected clusters with a pi donor ligands (e.g. metal halo species) in which metal-metal bonding is important. Chapter 8 introduces the area of polyoxometalates, closing with a short discussion of the wide range of applications.

Chapter

Cover Essentials of Inorganic Chemistry 1

Orbitals to oxidation state  

This chapter examines atomic orbitals. An atomic orbital is the wavefunction of an electron in an atom; its square gives the probability of finding the electron at that point. The Schrödinger solution defines the wave equation for the electron in the hydrogen atom as a product of a radial and angular part. The chapter then looks at organometallic compounds before considering the oxidation state, which is a formal device for partitioning electrons in a molecule in a chemically intelligent way. The oxidation state of an atom in a compound is the charge which would result if the electrons in each bond to that atom were assigned to the more electronegative atom.

Chapter

Cover Applications of Artificial Intelligence in Chemistry

Genetic algorithms  

This chapter talks about genetic algorithms (GA), which are considered an optimization technique. This is, in other words, an intelligent way to search for the optimum solution to a problem hidden in a wealth of poorer ones. It explains that a GA works with a ‘population’ of individuals. It also clarifies how the individuals ‘mate’ with each other, ‘mutate’, and ‘reproduce’ in order to evolve through successive generations toward an optimum solution. The chapter discusses what characteristic of evolution acquires the ability to provide the inspiration for solving numerical problems and how its power can be harnessed in a most effective and intriguing way. It mentions the similarities of GA with other optimization and search methods in which any computational task involves mating, mutation, and reproduction.

Chapter

Cover Elements of Physical Chemistry

Acid–base equilibria of salts in water  

This chapter studies the acid–base equilibria of salt solutions. The ions that a dissolved salt provide are themselves either acids or bases, sometimes both. Acidity constants can be used to predict the pH of solutions, and that information in turn can be used to account for the variation of pH during the course of a titration. That information is also helpful as a guide to the selection of solutes that stabilize the pH of solutions. The chapter looks at acid–base titrations, explaining how the pH of a mixed solution of a weak acid and its conjugate base is given by the Henderson–Hasselbalch equation. It then considers the buffer action, examining the buffer solution and differentiating between an acid buffer and a base buffer.

Chapter

Cover Drug Design and Development

Combinatorial Chemistry and High Throughput Screening  

This chapter explores combinatorial chemistry and high throughput screening. During the 1980s, a rapid increase in molecular biology techniques had resulted in the development of rapid, efficient drug testing systems, known as high throughput screening (HTS). These techniques were able to provide accurate results on extremely small quantities (μg) of test substances. However, in order to be used economically, HTS requires rapid production of very large numbers of test substances which could not be met by traditional synthesis. Combinatorial chemistry was developed to provide new test molecules in sufficient numbers to meet this need. The chapter investigates solid phase synthesis, solution phase synthesis, and polymer-assisted solution phase synthesis. It also considers chemical tagging, deconvolution, purification, combinatorial libraries, and chemogenomics.

Chapter

Cover Biological Science

Solutions  

Managing, Conserving, and Restoring Ecosystems

This chapter looks into solutions to the threats to ecosystems. Solutions addressing the threats can be largely grouped under the following: protection, management, conservation, and restoration of ecosystems. The chapter explains how conservation can either occur in capacity or the wild. It clarifies that ecological management is not only about conservation as it involves managing ecological problems, such as a pest or disease damaging other species or human livelihoods. The key aspects of restoration ecology include recreating habitats, rewilding landscapes, and reintroducing species. The chapter also acknowledges the importance of other landscape-scale conservation approaches, such as working with farmers.

Chapter

Cover Making the Transition to University Chemistry

Thermochemistry  

This chapter focuses on thermochemistry. It starts with enthalpy change which is the heat added to a system at constant pressure. The reaction is considered endothermic if heat is taken, while it would be exothermic if heat is given out. As the chapter shows, a calorimeter can be used to measure enthalpy changes. According to Hess's law, the standard enthalpy change for a reaction is independent of the route taken from reactants to products. Atomization enthalpy, on the other hand, is the standard enthalpy change accompanying the formation of a gaseous atom from either a solid or a gas containing molecule. Finally, the chapter explains bond enthalpy, solution enthalpy, and hydration enthalpy as well.

Chapter

Cover Atkins’ Physical Chemistry

Activities  

This chapter describes how the extension of the concept of chemical potential to real solutions involves introducing an effective concentration called an ‘activity’. In certain cases, the activity may be interpreted in terms of intermolecular interactions; an important example is a solution containing ions. Such solutions often deviate considerably from ideal behaviour on account of the strong, long-range interactions between the charged species. The chapter shows how a model can be used to estimate the deviations from ideal behaviour when the solution is very dilute, and how to extend the resulting expressions to more concentrated solutions. It looks at the Margules equations, the Debye–Hückel theory, and the Debye–Hückel limiting law.

Chapter

Cover Interfacial Science

The gas-liquid interface: adsorption; films and foams; aerosols  

This chapter describes some of the most obvious and dramatic effects of adsorption that can be seen at the air-solution interface. It talks about liquid drops that change their shape, foams that can be formed on liquids that otherwise will not foam, and the rise of liquids in capillaries that is reduced. It also analyses the enhanced spreading of liquids over solid surfaces, the reduction of the ability of light winds to ruffle the surface of water in a pond, and soils that are wetted more readily by water. The chapter deals with the measurement of adsorption by analysis of the surface or by change in bulk phase concentration that is usually not feasible as the area of a gas-liquid interface is usually small and sample collection is often difficult. It explains how adsorption is normally determined from surface tension data using the Gibbs equation.