Popular in Principles of Chemistry II
Barbi Della Polla
verified elite notetaker
Popular in Chemistry
This 4 page Class Notes was uploaded by Barbi Della Polla on Friday February 13, 2015. The Class Notes belongs to CHM 112 at University of Miami taught by Vanessa Falcao in Spring2015. Since its upload, it has received 29 views. For similar materials see Principles of Chemistry II in Chemistry at University of Miami.
Reviews for Classes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/13/15
Class 0128 Chapter 17 Free Energy and Thermodynamics The Energy Tax every energy transition results in a loss of energy Conversion of energy to heat which is lost by heating up the surroundings Heat Tax fewer steps generally results in a lower total heat tax Heating with natural gas few steps Heating with electricity Thermodynamics and Spontaneity Thermodynamics predicts whether a process will occur under the given conditions Processes that will occur are called spontaneous Nonspontaneous processes require energy input to go Enthalpy in not the only factor which determines if a reaction is spontaneous or not Spontaneity is determined by comparing chemical potential energy of the system before the reaction with the free energy of the system after the reaction If a system after reaction has less potential energy the reaction is thermodynamically favorable Spontaneity is not equal to fast or slow Reversibility of Process Any spontaneous process is irreversible because there is a net release of energy when it proceeds in that direction It will proceed in only one direction A reversible process will proceed back en forth between the two conditions Reversible process is at equilibrium This results in no change in free energy If a process is spontaneous in one direction it must be nonspontaneous in the opposite direction De carro nuevo a oxidado es espontaneo y de oxidado a nuevo no es espontaneo Comparing Potential Energy the direction of spontaneity can be determined by comparing the potential energy of the system at the start and the end Ex the guy pulling the rope is doing some work therefore there is a high potential energy The direction of spontaneous change will be the opposite Ex 2 dissolving a salt is an endothermic and spontaneous reaction The chemical potential of the salt is high so when Class 0128 dissolving the direction of the spontaneous change will be low dissolved ions Diamond Graphite graphite is more stable than diamond so the conversion of diamond into graphite is spontaneous slow rate Spontaneous Processes Occur because they release energy from the system Exothermic from syst higher potential energy lower potential energy Endothermic from syst of lower potential energy syst of higher potential energy 0 Combustion is always spontaneous Melting Ice 0 When a solid melts the particles have more freedom of movement 0 More freedom of movement increases the randomness of the system Entropy when the systems become more random energy is released Entropy is in uenced by temperature Entropy increase from solid to liquid to gas Decrease from gas liquid solid Water Evaporating endothermic Increasing entropy from a more organized structure to a less one liquid to gas Factors Affecting Whether a Reaction is Spontaneous 1 Enthalpy change AH is the difference in the sum of the internal energy and PV work energy of the reactants to the products 2 Entropy change AS is the difference in randomness of the reactants compared to the products Enthalpy Change kJmol Stronger bonds more stable molecules Exothermic negative AH AS is favorablefinal condition is more random than the initial positive Endothermic positive AH AS is unfavorable nal condition more ordered than initial negative Class 0128 Entropy is a thermodynamic function that increases as the numbers of energetically equivalent ways of arranging the components increases S S jmol S k in W K Boltzman constant 138x103923JK W is the number of energetically equivalent unitless Random systems require less energy than ordered ones W energetically equivalents states for the expansion of gas One of these states are more probable than the other two Review micro and macrostates PPT Change in Entropy AS A522 S nal 39 Entropy change is favorable when the result is a more random system AS is positive Changes that increase the entropy Reactions whose products are in a more random state Solid more ordered than liquid liquid more ordered than gas Reactions that have larger numbers of product molecules than reactant molecules Increase in temperature Solid dissociating into ions upon division For processes where the nal condition is more random than the initial AS system is positive and the entropy change is favorable for the process to be spontaneous For processes where the nal condition is more ordered than the initial AS system is negative and the entropy change is unfavorable for the process to be spontaneous A Ssystem A I r Sreaction 2 Im Entropy change in state change When the materials change state the numbers of macrostates it can have changes as well Class 0128 The more degrees of freedom the molecules have the more macrostates are possible Solids have fewer macrostates than liquids which have fewer macrostates than gases Less macro more micro Ssolid lt Sliquid lt Sgas Second Law of Thermodynamics The total entropy change of the universe must be positive for a process to be spontaneous For reversible process A Sumverse 0 For irreversible spontaneous process A Suniversegt 0 If the entropy of the system decreases the entropy of the surroundings must increase by a larger amount When A Ssystem is negative A Ssurroundings must be positive and big for a spontaneous process A Suniverse A r A Ssystem
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'