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BSC. -II PHYSICAL CHEMISTRY THERMODYNAMICS-II
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It does not give information concerning feasibility of a thermodynamic process. NOT EXPLAINED BY FIRST LAW
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It tells that work obtained is equal to heat absorbed but in actual heat absorbed can not be completely converted into work. Limitations motivating second law
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5 The second law of thermodynamics It will arouse changes while the heat transfers from low temp.substance to high temp. one.
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All spontaneous processes are thermodynamically irreversible..
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The complete conversion of heat into work is impossible without leaving its effects somewhere. SOME AMOUNT OF HEAT MOVES TO SURROUNDING
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Without the use of any external agency,heat can not by itself pass from a colder body to a hotter body HOT BODY COLD BODY HEAT TRANSFER EXTERNAL AGENCY
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Sadi Carnot devised a technique, called Carnot Cycle. Carnot chose a reversible heat engine,.known as carnot engine, consisting of one mole of ideal gas, fitted with frictionless piston,insulated on all sides except bottom. This engine is having 2 heat reservoirs, one at higher temperature T 2 and the other at a lower temperature T 1. The Carnot Cycle consists of 4 different operations: 1.Isothermal expansion 2.Adiabetic expansion 3.Isothermal compression 4.Adiabetic compression
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ISOTHERMAL(T 2 ) ISOTHERMAL(T 1 ) ADIABETIC I II III IV PRESSURE VOLUME
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State 1 T 2 State 2 T 2 State 4 T 1 State 3 T 1 isothermal adiabatic isothermal q=0, W 4 =C v T q=0, w 2 =-C V T w 1 = -RT 2 ln(V2/V1) q 2 =-w w 3 = RT 1 ln(V4/V3) -q 1 =w 3
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State 1 T hot State 2 T hot State 4 T cold State 3 T cold isothermal adiabatic isothermal q=0, w=C V T q=0, w=-C V T w= -nRT hot ln(V2/V1) q=-w w= -nRT cold ln(V4/V3) q=-w
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114 The second law of thermodynamics It will arouse changes while the heat transfers from low temp.substance to high temp. one.
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121 The second law of thermodynamics It will arouse changes while the heat transfers from low temp.substance to high temp. one.
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