tailieunhanh - Modern Analytical Cheymistry - Chapter 6

Equilibrium Chemistry 186 6. Multilayer Structures 6 Multilayer Structures Fig. Multilayer dielectric slab structure. Higher-order transfer functions of the type of Eq. () can achieve broader reflectionless notches and are used in the design of thin-film antireflection coatings, dielectric mirrors, and optical interference filters [615–677,737–770], and in the design of broadband terminations of transmission lines [805–815]. They are also used in the analysis, synthesis, and simulation of fiber Bragg gratings [771–791], in the design of narrow-band transmission filters for wavelength-division multiplexing (WDM), and in other fiber-optic signal processing systems [801–804]. They are used routinely in making acoustic tube models. | Chapter Equilibrium Chemistry egardless of the problem on which an analytical chemist is working its solution ultimately requires a knowledge of chemistry and the ability to reason with that knowledge. For example an analytical chemist developing a method for studying the effect of pollution on spruce trees needs to know or know where to find the structural and chemical differences between p-hydroxybenzoic acid and p-hydroxyacetophenone two common phenols found in the needles of spruce trees Figure . Chemical reasoning is a product of experience and is constructed from knowledge acquired in the classroom the laboratory and the chemical literature. The material in this text assumes familiarity with topics covered in the courses and laboratory work you have already completed. This chapter provides a review of equilibrium chemistry. Much of the material in this chapter should be familiar to you but other ideas are natural extensions of familiar topics. 135 36 Modern Analytical Chemistry OH OH a b Figure Structures of a p-hydroxybenzoic acid and b p-hydroxyacetophenone. Time Figure Change in mass of undissolved Ca2 and solid CaCO3 over time during the precipitation of CaCO3. equilibrium A system is at equilibrium when the concentrations of reactants and products remain constant. -6A Reversible Reactions and Chemical Equilibria In 1798 the chemist Claude Berthollet 1748-1822 accompanied a French military expedition to Egypt. While visiting the Natron Lakes a series of salt water lakes carved from limestone Berthollet made an observation that contributed to an important discovery. Upon analyzing water from the Natron Lakes Berthollet found large quantities of common salt NaCl and soda ash Na2CO3 a result he found surprising. Why would Berthollet find this result surprising and how did it contribute to an important discovery Answering these questions provides an example of chemical reasoning and introduces