ch6notes - Chapter 6 Thermochemistry 2010 Donald L. Siegel,...

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©2010 Donald L. Siegel, All Rights Reserved Chapter 6 Chapter 6 Thermochemistry
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©2010 Donald L. Siegel, All Rights Reserved What is What is thermochemistry thermochemistry ? ? W Chemical equations tell us what and how much reacts W There is more to chemical reactions Some reactions release energy Some reactions require energy W The study of the relationship between energy and chemical reactions is thermochemistry
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©2010 Donald L. Siegel, All Rights Reserved The 1 The 1 st st Law of Law of Thermodynamics Thermodynamics W Thermochemistry is all about transfers of energy W Thermodynamics is the study of energy transfers W The first law of thermodynamics is conservation of energy Energy can neither be created nor destroyed “You can’t win.”
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©2010 Donald L. Siegel, All Rights Reserved Energy transfers Energy transfers W Energy transfers are directional System is whatever we are considering Surroundings are everything else W Types of energy kinetic energy potential energy electrical W We are only considering kinetic energy W Random motion due to kinetic energy called thermal motion
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©2010 Donald L. Siegel, All Rights Reserved Energy and Work Energy and Work W Total energy contained in a system is called the internal energy U We can only measure changes in U, U U=q+w q is heat absorbed by the system w is work done to the system W Sign of q and w only matters when used with a state function W Most of these problem are unit conversions w might be in L atm U usually in J
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©2010 Donald L. Siegel, All Rights Reserved Energy and work Energy and work W Energy represents the ability to do work W w = F × s W P = F/A W P × V = F/A ×V = F×s=w kg m -1 s -2 ×m 3 = kg m 2 s -2 = J W Mostly, we are concerned with PV work W That means w = -P Δ V, in terms of work done to the system
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©2010 Donald L. Siegel, All Rights Reserved
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©2010 Donald L. Siegel, All Rights Reserved State functions State functions W A function that only depends on the initial and final states is called a state function W A function that DOES depend on how it got from point A to point B is called a path function W Examples of state functions altitude bank balance distance between 2 places W Examples of path functions distance travelled q total amount spent each month
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©2010 Donald L. Siegel, All Rights Reserved
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©2010 Donald L. Siegel, All Rights Reserved
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©2010 Donald L. Siegel, All Rights Reserved Ways Compounds Absorb Energy Ways Compounds Absorb Energy W Amount of energy required to increase temperature is called heat capacity W In ideal gases, three ways to absorb energy Translations: move the whole molecule Rotations: rotate the molecule about an axis Vibrations: change the orientation of the atoms to each other in the molecule
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©2010 Donald L. Siegel, All Rights Reserved Another vibration
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©2010 Donald L. Siegel, All Rights Reserved What is heat?
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This note was uploaded on 03/08/2011 for the course CHEM 161 taught by Professor Vacillian during the Fall '08 term at Rutgers.

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ch6notes - Chapter 6 Thermochemistry 2010 Donald L. Siegel,...

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