Class Note for CHEM 112 at UMass(36)
Class Note for CHEM 112 at UMass(36)
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This 14 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Massachusetts taught by a professor in Fall. Since its upload, it has received 16 views.
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Date Created: 02/06/15
Turn on Camtasia Recording The exams were dropped off to be graded Wednesday morning The data are not yet back We are starting chapter 19 the cocktail party chapter What does your room look like Perfectly orderly Afewthinvs out of lace Pretty messy A complete disaster A tornado hit NUDE 2nd Law of Thermodynamics The universe tends to greater and greater disorder a quot A H aMolecules are like undergraduates They like to leave theiro tionso en 1 w p p a a lodge m flue A reaction is spontaneous if disorder entropy for the universe is positive WWI equilibrium W e results in the dispersal of energy 3 ll 2nd Law of Thermodynamics The universe tends to greater and greater 0 disorder a m 4 H H a Molecules are like undergraduates They like ll m39 lj Hodxw39llwmt a eave elr up one upen a Wm M Areaclion is spontaneous il disorder entropy for the universe is positive my Wye 1w Wlh d lWII resulls in me dispersal amen Why does Entropy exist There are so many ways to be Es and only one way to be tidy Place for everything and everything in it s place I Why does Entropy exlmad There are so many ways to be messy and only one way to betidy ordinal Place for everything and everything in its place mot wz o Statistics 51 4 9w 6 10 Poker cards Directionality of Reactions Probability suggests that a spontaneous reaction will result in the dispersal Ofm or of or W Matter Dispersal Due last night in OWL 15139 Law of Thermodynamics What is lost by me is gained by you Energy is neither created or destroyed The law of conservation of energy Change in the internal energy of the system is the sum of the heat transferred to or from the system and the work done on or by the system What is the definition of system TWUQP Endothermic System Surroundings Exothermic Enthalpy State Function 5 Gives off heat Consumes heat Heat of formation at constant pressure Part of the universe we are studying The rest of the universe Function that is only determined by the initial and final states but is independent of path What is the definition of Exothermic TWUQP System Surroundingy Exothermic 3 Endothermic 4 Enthalpy State Function 5 6 AM Gives off heat Consumes heat Heat of formation at constant pressure Part of the universe we are studying The rest of the universe Function that is only determined by the initial and final states but is independent of path 10 What is the de nition of State Function A System 1 Gives off heat B Surroundings 2 Consumes heat c Exothermic 3 Heat of formation at constant pressure D39 EndOtherm39C 4 Part of the universe we are E Enthalpy studying F State Function 5 The rest of the universe 6 Function that is only determined by the initial and final states but is independent of path 11 QB M MAL disorder A A 33 quot02quot it W WV 361 WP AG 1A8 12 Spontaneous Tells us about the drive to equilibrium Tells us nothing about the rate a A chemical system at equilibrium will never spontaneously change in a way that results in the system no longer being in equilibrium 13 Directionolity of Reactions How probable is it that reactant molecules will react PW suggests that a spontaneous reaction will result in the dispersal of energy or of matter or ofenergy amp matter 14 Directionali ty of Reactions Probability suggests that a spontaneous reaction will result in the dispersal of energy or of matter or both Energy Dispersal 15 Directionali ry of Reactions 39 Energy Dispersal Exothermic reactions involve a release of stored chemical potential energy to the surroundings The stored potential energy starts out in a few molecules but is finally dispersed over a great many molecules The final state with energy dispersed is more probable and makes a reaction spontaneous 15 J and A 0 M Aims is W015 wow 122215 q 9 a 5 169 w 25 E Q 9 0 EXZESZQUXEEESB c 13 2 4 2 3 4 3394 53 A 6 6quantaof 5 energy 2 lt2 4 3 gt 3 O O 2 1 0 o o 18 ENERGY QUANTA mewbmm Wcsol 42H 8 MWVVESW i Number of different ways to achieve this arrangement 4 o 4 12a 12 12 24 6 396 4 919 0 20 Ell ERGY LEVELS Gas expands into a new container with twice the volume Energy levels for a gas in a container Shading indicates the total energy available EHERGY LEVELS Energy levels for a gas in a new container with twice the volume More energy states are now available with the same total energy The states are closer together 21 22 En39rr39opy S S JlKmol H20iq 6995 HZOgas 1888 S gases gt Squuids gt Ssolids 23 En rr opy and S ra res of Ma r rer S Br2 liq lt S Br2 gas S H20 sol lt S H20 liq 24 Entropy S Entropy of a substance increases with temperature Molecular motions Molecular motions of of heptane C7H16 heptane at different temps Wmnc w a m K g 5quot 21Jx m 25 Entropy S 5v JK moi Increase in molecular complexity generally 1353 leads to increase in S 2292 Y J ethane Meme ne CH4 2703 a J pinpane 25 Entropy S Entropies of ionic solids depend on coulombic attractions so JIKmol MgO 269 NaF 515 M92 amp02 Na amp F39 27 Entropy S Entropy usually increases when a pure liquid or solid dissolves in a solvent a lean alan Dado aco no9 z
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