TAILIEUCHUNG - Ebook General chemistry principles and modern applications (10th edition): Part 2
(BQ) Part 2 book "General chemistry principles and modern applications" has contents: Chemistry of the living state, reactions of organic compounds, structures of organic compounds, nuclear chemistry, complex ions and coordination compounds, the transition elements,.and other contents. | 7 Thermochemistry CONTENTS 7-1 7-2 7-3 7-4 7-5 7-6 7-7 7-8 7-9 Getting Started: Some Terminology Heat Heats of Reaction and Calorimetry Work The First Law of Thermodynamics Heats of Reaction: *U and *H Indirect Determination of *H: Hess s Law Standard Enthalpies of Formation Fuels as Sources of Energy Potassium reacts with water, liberating sufficient heat to ignite the hydrogen evolved. The transfer of heat between substances in chemical reactions is an important aspect of thermochemistry. N Thermochemistry is a subfield of a larger discipline called thermodynamics. The broader aspects of thermodynamics are considered in Chapters 19 and 20. * atural gas consists mostly of methane, CH 4. As we learned in Chapter 4, the combustion of a hydrocarbon, such as methane, yields carbon dioxide and water as products. More important, however, is another product of this reaction, which we have not previously mentioned: heat. This heat can be used to produce hot water in a water heater, to heat a house, or to cook food. Thermochemistry is the branch of chemistry concerned with the heat effects that accompany chemical reactions. To understand the relationship between heat and chemical and physical changes, we must start with some basic definitions. We will then explore the concept of heat and the methods used to measure the transfer of energy across boundaries. Another form of energy transfer is work, and, in combination with heat, we will define the first law of thermodynamics. At this point, we will establish the relationship between heats of reaction and changes in internal energy and enthalpy. We will see that the tabulation of the change in internal energy and change in enthalpy can be used to calculate, directly or indirectly, energy changes during chemical and physical changes. Finally, concepts introduced in this chapter will answer a host of practical questions, such as 241 242 Chapter 7 Thermochemistry why natural gas is a better fuel than coal and why .
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