Weekly Notes 9.21 - 9.25
Weekly Notes 9.21 - 9.25 CHE140
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This 6 page Class Notes was uploaded by Brittany Notetaker on Friday September 25, 2015. The Class Notes belongs to CHE140 at Illinois State University taught by Dr. Chris Hamaker in Summer 2015. Since its upload, it has received 61 views. For similar materials see General Chemistry I in Chemistry at Illinois State University.
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Date Created: 09/25/15
CHE140 Notes 9212015 9252015 Sept 21 Lecture I C102aq I I 139aq I 9 I 12aq I I C139aq Break apart the equation into half equations we ll do the Cl equation rst then the 1 and put them together C102aq 9 C139 C1 4 C1 1 O 2 Difference of 5 electrons from the left side to the right side 4 1 5 Balance the oxygen by adding water then balance the hydrogen 4H C102 9 C139 2H20 Add the difference in electrons 5e39 4H C102 9 C139 2H20 11 10 Balance the equation 2139 9 12 No oxygen so no need to add water or hydrogen Add the difference of electrons 2139 9 12 2e39 Multiply the two equations to make the number of electrons on each side equal Multiply the C1 equation by 2 and the I equation by 5 Set them equal to each other and cancel out what s possible 8H 2C102 10139 9 2Cl39 512 4H20 Thermochemistry 0 The study of energy changes in chemical reactions 0 the capacity to transfer heat or to do work Potential Energy PE mgh mass x gravity x height 0 Potential energy is a state function 0 Doesn t matter how the object got Where it did the potential energy stays the same Kinetic Energy KE 12 mu2 0 Energy of motion 0 Temperature is a measure of average kinetic energy Electrostatic Energy Eel QQ Q are charges d is distance d Systems 0 A system is a specific process you are looking at Surroundings are everything else neither energy nor matter is exchanged with the surroundings 0 Perfect thermos o heat can be exchanged with the surroundings but not matter 0 A jar of peanut butter 0 heat and matter can be exchanged with the surroundings o Pouring coffee into a cup Endothermic processes gain heat from their surroundings q system gt O Exothermic processes lose heat to their surroundings q system lt 0 Sept 23 Lecture evaporatiun 339 rc n ensatin its Internal Energy 0 The sum of kinetic energy and potential energy in a systemAA 0 Is a state function same energy no matter how you get there Energy Units 0 Calorie cal the amount of heat energy required to raise 1 g of water from 145 C to 155 C or just a degree C o A nutritional calorie is abbreviated Cal 0 The 81 metric system unit of energy is the Joule J o 1cal 41845 AB q W q is heat W is work 0 Can either have work done Q the system by the surroundings that increases the intern energy wgt0 0 Or have work done by the system on the surroundings that decreases the internal energy wlt0 AE gt0 the system gains internal energy 9 endothermic lt0 the system loses internal energy 9 exothermic qgt0 system gains heat qlt0 system loses heat Enthalpy H and Enthalpy Change AH AH AE PAV 0 enthalpy the ow of energy into or out of a system at constant pressure 0 AHgt0 endothermic o AHlt0 exothermic Heating and Cooling Curves o Molar heat capacity Cp is the amount of energy required to heat one mole of a substance 1 C 0 For temperature changes q n X Cp X AT 0 n moles of a substance 0 AT temperature change 1 How much energy is needed to heat 241 g water from 100 C to 75 0 C H20l Cp 753Jmol x C AT 650 C 241 g 1mol 753 650 C 1802g mol X C 655 x 1031 q Sept 25 Lecture Temperature Changes qnXCpXAT ATq nXCp Phase Change q AHtransition X n AHqu S 6 9 L Fusion For H20 601kJm01 AHvap L 6 9 G Vaporization For H20 4067 kJmol AHsub S 6 9 G Sublimation 1 How much energy is required to melt 521g of water 521g 1 mol H20 601kJ 1802g H20 1 mol 171kJ Cp H20s 371 Jm01X OC Cp H201 753 Jm01X OC Cp H20g 336 Jm01X OC Heating Curves Heating Curve 35 25 15 05 qadded N w 1 Tb Tf From 01 the solid is heating From 11 the solid is melting From 12 the liquid is heating From 22 the liquid is vaporizing From 23 the gas is heating Endothermic reaction Cooling Curve Cooling Curve 6 5 5 5 4 4 q lost From 65 the gas is cooling From 55 the gas is condensing From 54 the liquid is cooling From 44 the liquid is solidifying From 43 the solid is cooling Exothermic reaction Solid heatcool q n X Cps X AT Meltingfreezing q n X AHfus Liquid heatcool q n X Cpl X AT Vaporizingcondensing q n X AHVap Gas q n X Cpg X AT 0 Calculate q for each step and add together for total energy 0 All heating curves Will be positive all cooling curves Will be negative V w Tb Tr Heat Transfer 0 Two systems in contact With each other Will exchange heat until their temperatures are the same 0 This is thermal equilibrium 0 qlost 39qgained How do we determine Cp values 0 Calorimetry calorimeter qcalorimeter Ccalorimeter X AHreaction Standard EnthalpV formation AHOf of standard condition 0 Standard enthalpy formation is the enthalpy of change at a constant pressure When one mole of a substance is produced from its elements AHOf for elements in their standard state is ZERO AHOf 02g OkJmol AHOf Hgl OkJmol
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