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Chapter

Cover Thermodynamics of Chemical Processes

Equilibrium in chemical reactions  

This chapter applies the concept of Gibbs energy to describe the factors that govern chemical equilibrium. It determines how far a reaction will go before it comes to equilibrium and how to find the equilibrium yield and make predictions about the effect that changed the experimental conditions on equilibrium. It also discusses the Gibbs energy of the system which changes throughout a reaction, depending on the proportions of reactants and products. The chapter mentions an equilibrium reaction with straightforward stoichiometry, such as the reaction of dinitrogen tetroxide to form nitrogen dioxide. It points out how adding or removing one of the components of a reaction affects the activity of the other components in the equilibrium mixture, since it will change the mole fractions.

Book

Cover Making the Transition to University Chemistry

Michael Clugston, Malcolm Stewart, and Fabrice Birembaut

Making the transition to university chemistry aims to help students make the significant step from school to university, setting them up to be confident and successful in their chemistry studies. The book begins by looking at the basic atomic structure, bonding, and molecular shape. There is a chapter on moles. The text turns to the different states of matter after that. There are also chapters on thermochemistry, chemical equilibrium, and acid-base equilibrium. The middle of the book moves on to look at redox reactions, spontaneous change, entropy, and Gibbs energy. The periodic table is also examined, as are the halogens and transition metals. Hydrocarbons are considered. Towards the end, the text moves on to aldehydes and ketones, carboxylic acids and their derivatives, polymers, and instrumental analysis.

Chapter

Cover Statistical Thermodynamics

From molecule to mole: the canonical partition function  

This chapter discusses the canonical partition function (Q). It notes that the molecular partition function contains all the thermodynamic information about a system of independent particles at equilibrium. Additionally, the chapter highlights the molecular partition function as being the number of energy states accessible to the system at a given temperature. The chapter notes the system wherein energy states are no longer constant and fluctuate over time. The canonical partition function Q does not rely on the premise of individual particles interacting with each other. Additionally, Q provides a major tool that can be used when looking at increasingly complex situations such as understanding the relationship between the molecular partition function and the canonical partition function.

Chapter

Cover Electrode Potentials

Allowing for non-ideality: activity coefficients  

This chapter reviews the development of the relationship between activity and concentration, illustrating the chemical potential of an ideal solution that depends on whether it deals with the concentrations or mole fractions. It shows how the enthalpy of mixing is zero for ideal solutions, which can be interpreted in the terms that the intermolecular forces between the molecules in the mixture are equal to those in the pure liquids. It also points out that the equality of interaction forces is considered as an alternative way of describing an ideal solution. The chapter emphasizes that non-ideality must arise from grossly dissimilar inter-particular forces. It considers that electrodes and their potentials must use activities rather concentrations when opting for the Nernst equation.

Chapter

Cover Making the Transition to University Chemistry

Moles  

This chapter explores different types of formulae in chemistry: empirical formula and molecular formula. It defines empirical formula as the simplest whole-number ratio of atoms of each element in a compound. Molecular formula can be defined as the whole-number multiple of the empirical formula. The chapter also explains the value of the Avogadro constant, which is the number of atoms per mole. It notes the strategies for solving mass-to-mass calculations, ideal gas models, molar concentration, and molar volume. Molar mass is defined as the mass per mole of a substance. A solution is mostly expressed through mass concentration. This specifies the mass of the solute dissolved per cubic decimetre of the solution.

Chapter

Cover Atkins’ Physical Chemistry

The thermodynamic description of mixtures  

This chapter evaluates the thermodynamic description of mixtures. It develops the concept of chemical potential as an example of a partial molar quantity and explores how the chemical potential of a substance is used to describe the physical properties of mixtures. The key idea is that at equilibrium the chemical potential of a species is the same in every phase. By making use of the experimental observations known as Raoult's and Henry's laws, it is possible to express the chemical potential of a substance in terms of its mole fraction in a mixture. The chapter looks at the Gibbs–Duhem equation, as well as ideal–dilute solutions.

Book

Cover Chemistry for the Biosciences
Chemistry for the Biosciences explores all of the essential chemical concepts that students of biology need to know and understand. It starts by looking at atoms as the foundations for life, and how chemical bonding brings together atoms to form molecules and compounds. It also considers the interactions that operate between molecules, and what the chemical and biological implications of these interactions are. After considering a range of quantitative concepts relevant to the study of biology – moles, concentrations, and dilutions – it discusses the molecular basis of organic chemistry by considering hydrocarbons and functional groups. The text moves on to consider isomerism, molecular shape and structure, and the structure and function of key biological macromolecules. After explaining why metals have an important role in biological systems, it goes on to explore what happens during chemical reactions, and introduces oxidation, and reduction. It then explores concepts from the field of physical chemistry that are vital our understanding of life: energy, equilibria, and kinetics. After exploring acids, bases and buffers and their importance to biological systems, it concludes with a review of how we can use chemical analysis to better understand biological molecules.

Chapter

Cover Chemistry for the Biosciences

Moles, concentrations, and dilutions: making sense of chemical numbers  

This chapter details the language of measuring chemical quantities, focusing on one quantity in particular: the mole. The mole is a convenient way of scaling down large numbers: one mole of atoms represents 6 × 1023 atoms. The molar mass is the mass of one mole of a substance. The concentration of a solution tells us how much of a substance is present in a particular volume of that solution. When preparing solutions according to percentage by weight, one uses a mass of substance that equates to a certain percentage of the volume of the final solution. The chapter then looks at dilutions, explaining how the number of moles of the solute remain the same after dilution, but the total volume increases, so the concentration decreases. The chapter also highlights some of the tools for measuring concentrations, including titrations, UV-visible spectroscopy, atomic emission spectroscopy, and fluorescence spectroscopy.