Thermodynamics

Thermodynamics - Chemical Thermodynamics David A Katz...

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Chemical Thermodynamics David A. Katz Department of Chemistry Pima Community College Tucson, AZ 85709, USA
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irst Law of Thermodynamics First Law of Thermodynamics • The First Law of Thermodynamics was expressed in the study of thermochemistry. It is commonly known as the Law Conservation of Energy: he total energy of the universe is a The total energy of the universe is a constant. Energy cannot be created nor destroyed. Energy can be converted from one form to another or transferred from a system to the surroundings or vice versa.
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pontaneous Processes Spontaneous Processes • Spontaneous processes are ose that once started can those that, once started, can proceed without any outside intervention. • The term “spontaneous” has nothing to do with the time or rate f the process of the process. • In the diagram, when the valve is opened, the gas in flask B will spontaneously effuse into flask A , but once the gas is in both flasks, will ot pontaneously go back it will not spontaneously go back to one flask
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pontaneous Processes Spontaneous Processes • Diamond is ermodynamically favored thermodynamically favored to convert to graphite, but not kinetically favored. Paper burns — a product- favored reaction. Also kinetically favored once reaction is begun.
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pontaneous Processes Spontaneous Processes Processes that are pontaneous in one spontaneous in one direction are onspontaneous in the nonspontaneous in the reverse direction. In this example, an iron nail, in contact with the ir will rust air, will rust. To reverse the process omething must be done something must be done to the system.
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pontaneous Processes Spontaneous Processes • Processes that are spontaneous at one temperature may be nonspontaneous at other temperatures. • Above 0 C it is spontaneous for ice to melt. • Below 0 C the reverse process is spontaneous.
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pontaneous Processes Spontaneous Processes In general, spontaneous reactions are exothermic. Fe 2 O 3 (s) + 2 Al(s) 2 Fe(s) + Al 2 O 3 (s) H rxn = - 848 kJ (This is known as the (This is known as the Thermite Thermite reaction) reaction)
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The Thermite Reaction The thermite reaction was discovered in 1893 and patented in 1895 by German chemist Hans Goldschmidt. Goldschmidt was originally interested in producing very pure gy p g y p metals by avoiding the use of carbon in smelting, but he soon realized the value in welding. The first commercial application was the welding of tram tracks pp g in Essen, in 1899.
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eversible Processes Reversible Processes Nicolas Léonard Sadi Carnot (1796 – 1832) In an 1824 book Réflexions sur la puissance motrice du feu ("Reflections on the Motive Power of Fire"), he discussed the relation between heat and mechanical energy and presented an idealized steam engine that could be used to understand and clarify the fundamental principles that are of general applicability to all heat engines, independent of the particular design choices that might be made.
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eversible Processes Reversible Processes
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This note was uploaded on 12/07/2011 for the course CHEM 152 taught by Professor Staff during the Spring '08 term at Pima CC.

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Thermodynamics - Chemical Thermodynamics David A Katz...

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