6. Thermochemistry - Thermochemistry Chapter 6 Energy is...

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Thermochemistry Chapter 6
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Energy is the capacity to do work Radiant energy comes from the sun and is earth’s primary energy source Thermal energy is the energy associated with the random motion of atoms and molecules Chemical energy is the energy stored within the bonds of chemical substances Kinetic energy is the energy stored in a moving object Potential energy is the energy available by virtue of an object’s position
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Heat is the transfer of thermal energy between two bodies that are at different temperatures. Energy Changes in Chemical Reactions Temperature is a measure of the thermal energy . 90 0 C 40 0 C greater thermal energy Temperature = Thermal Energy
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Thermochemistry is the study of heat change in chemical reactions. The system is the specific part of the universe that is of interest in the study. open Exchange: closed energy isolated nothing SYSTEM SURROUNDINGS
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Exothermic process is any process that gives off heat – transfers thermal energy from the system to the surroundings. Endothermic process is any process in which heat has to be supplied to the system from the surroundings. 2H 2 ( g ) + O 2 ( g ) 2H 2 O ( l ) + energy H 2 O ( g ) H 2 O ( l ) + energy energy + 2HgO ( s ) 2Hg ( l ) + O 2 ( g ) energy + H 2 O ( s ) H 2 O ( l )
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Exothermic Endothermic
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Enthalpy (H) is used to quantify the heat flow into or out of a system in a process that occurs at constant pressure. H = H (products) – H (reactants) H = heat given off or absorbed during a reaction at constant pressure H products < H reactants H < 0 H products > H reactants H > 0
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Thermochemical Equations H 2 O ( s ) H 2 O ( l ) H = 6.01 kJ Is H negative or positive? System absorbs heat Endothermic H > 0 6.01 kJ are absorbed for every 1 mole of ice that melts at 0 0 C and 1 atm.
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CH 4 ( g ) + 2O 2 ( g) CO 2 ( g) + 2H 2 O ( l ) H = -890.4 kJ Is H negative or positive? System gives off heat
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This note was uploaded on 04/10/2010 for the course CHM CHM101 taught by Professor Woljaong during the Fall '07 term at Multimedia University, Cyberjaya.

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6. Thermochemistry - Thermochemistry Chapter 6 Energy is...

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