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Chapter

Cover Elements of Physical Chemistry

Partial molar quantities  

This chapter discusses partial molar quantities. When a substance is a component of a mixture, it makes a contribution to the properties of the mixture that depends on the composition. For a general description of the thermodynamics of mixtures, it is necessary to introduce other ‘partial’ properties. A partial molar property is the contribution (per mole) that a substance makes to an overall property of a mixture. The easiest partial molar property to visualize is the partial molar volume. The chapter then considers how the concept of a partial molar quantity can be applied to other state functions. The most important is the partial molar Gibbs energy, which is the chemical potential of a component. The chapter also looks at spontaneous mixing.

Chapter

Cover Biomedical Science Practice

Preparing and measuring reagents  

Ian Graham

This chapter details the process of preparing and measuring reagents, which are essential and fundamental skills for all biomedical scientists. The use of balances for weighing and pipettors and other volume measurement methods for volume delivery are key techniques in the production of solutions and their dilution. For correct operation, balances must be appropriately sited and calibrated. Burettes, pipettes, and volumetric flasks provide high levels of accuracy if used correctly. However, pipettors are the volume measurement tool of choice for highly accurate and precise work. They use disposable tips for convenience, require calibration, and, being precision instruments, must be used with care. The chapter then looks at molar concentrations and alternative ways of expressing concentration.

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

Thermodynamic aspects of phase transitions  

This chapter examines how thermodynamic arguments explain the appearance of phase diagrams and can be used to make predictions about the effect of pressure on phase transitions. They provide insight into the properties that account for the behaviour of matter under different conditions. The effect of temperature and pressure on the chemical potential of a substance in each phase depends on its molar entropy and molar volume, respectively. The chemical potential of a substance decreases with increasing temperature in proportion to its molar entropy; it increases with increasing pressure in proportion to its molar volume. Meanwhile, the vapour pressure of a condensed phase increases when pressure is applied. The chapter then looks at the Clapeyron equation, which is an exact expression for the slope of a coexistence curve. The Clausius–Clapeyron equation is an approximate expression for the coexistence curve of a condensed phase and its vapour.