Note for CH 104 with Professor Woski at UA-Study Guide Exam 3
Note for CH 104 with Professor Woski at UA-Study Guide Exam 3
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This 4 page Study Guide was uploaded by an elite notetaker on Friday February 6, 2015. The Study Guide belongs to a course at University of Alabama - Tuscaloosa taught by a professor in Fall. Since its upload, it has received 20 views.
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Date Created: 02/06/15
Exam 3 Outline CH 104 F all 2009 You need to bring a pencil a calculator and your ACT card ALL 0th er materials must be left at th e front of the classroom in an unsecured area ALL cellphones must be turned off during exam Chapter 7 Chemical Reactions Energy Rates and Equilibrium 1 Energy in chemical reactions enthalpy changes sections 72 amp 73 Heat of reaction AH describes the heat released negative AH exothermic or heat absorbed positive AH endothermic in a reaction Activation energy is the barrier that must be overcome for any reactions to proceed and represents the energy of breaking bonds in the reactants Energy diagrams pp 194196 can be used to represent the energy changes in a reactionibe able to interpret these diagrams Heat can be considered a reactant in a balanced chemical reaction 0 Coefficient of heat is 1 this can be used to relate the heat to the molar quantities coefficients of the other reactants and products 2 Free energy section 74 Free energy change AG depends on enthalpy heat change entropy change in disorder and temperature in Kelvins Entropy is the amount of disorder in a system 0 AS positive then disorder increases more favorable 0 AS negative then disorder decreases o Gases are more disordered than liquids which are more disordered than solids AG AH TAS The AGs for spontaneous processes are negative exergonic while those for non spontaneous are positive endogonic 3 Rates sections 75 amp 76 Reactions proceed when collisions occur with enough energy to overcome the activation energy Rates depend on activation energies the barriers that must be overcome for any reaction to proceed that represents the energy of breaking bonds in the reactants Energy diagrams p 194 can be used to represent the energy changes in a reactioni be able to interpret these diagrams T temperatures andor concentrations increase reaction rates Catalysts increase rates by lowering activation energies and are not consumed in reaction 4 Equilibrium sections 7779 o Reversible reactions section 77 0 Both forward and reverse reactions occur 0 Equilibrium eXists when reactants are consumed at the same rate they are formed 0 Equilibrium constant K section 78 0 Ratio of concentrations of products over reactants equals a constant at equilibrium 0 Concentration of each product and reactant is raised to the power of its coefficient in a balanced reaction Be able to write equilibrium expressions Be able to calculate K when given equilibrium concentrations Reactions where K gtgt I favor products 0000 Reactions where K ltlt I favor reactants 0 Le Chatelier s Principle section 79 Be able to identi result of change I o Stressing a system in equilibrium will shift the equilibrium to relieve the stress 0 Adding compounds pushes the reaction in the opposite direction 0 Adding reactants pushes equilibrium to products 0 Adding products pushes equilibrium to reactants o Removing compounds pulls the reaction in the opposite direction 0 Removing reactants pulls equilibrium to reactants o Removing products pulls equilibrium to products 0 Heat can act like a reagent endothermic reaction or a product exothermic reaction Chapter 8 Gases Liquids amp Solids 0 Be able to define the properties that describe a gas liquid or solid sections 12 amp 81 0 Gas Takes shape of container variable volume compressible no intermolecular interactions 0 Liquid Takes shape of container constant volume moderate intermolecular interactions 0 Solid Definite shape constant volume strong intermolecular interactions 5 Gas Laws 0 0 You do not need to know the individual gas laws covered in 8386 Variables 0 V volume usually in liters o P pressure usually in atmospheres I 1 atm 760 torrmm Hg 0 T temperature given in kelvins or 0C must use K in calculations 0 n amount usually in moles or grams The combined gas law section 87 O P1V1 P2V2 T1 T2 Any variable that does not change can be dropped out of the equation Molar volume 0 Volume of 1 mole of any gas at STP is 224 L o STP 273 K and 1 atm The ideal gas equation section 89 0 PV nRT o R the gas constant 00821 L atmmole K Partial pressures section 810 o In a mixture of gases each gas exerts the same partial pressure as if it were in the container alone 0 The total pressure is the sum of the partial pressure of each gas Plum P1 P2 P3 Intermolecular Forces 0 Hydrogen bonding section 811 o This is the only force between molecules that you need to know 0 Hydrogen bonding is a dipoledipole interaction between and electronegative atom usually F O N and a hydrogen bonded to an electronegative atom usually F O N for example 70 H70 0 Increases the melting and boiling points of substances due to increased attraction between molecules 6 Changes of state sections 815 Temperatures do not change during changes of state Solidlt gtLiquid 0 Heat absorbed to melt solid and heat removed to freeze a liquid is the heat of fusion Heat of fusion for water is 80 calg Heat AHmsiun X mass Liquidlt gtGas o Liquids boil when their vapor pressures equal the atmospheric pressure 0 Heat absorbed to vaporize a liquid and heat removed to condense a gas is the heat of vaporization 0 Heat of vaporization of water is 540 cal g 0 Heat AHvapurizanun X mass Total heat absorbed or released by heating or cooling a substance can be determined by adding the heats for any changes in temperature of a substance in a given state to the heats of the changes in state Remember from chapter 2 Speci c Heat section 210 0 Speci c Heat SH is the amount of heat required to raise the temperature of exactly 1 g of a substance by exactly 1 OC Speci c heat of water 10 cag C Heat equation Heat SH X mass X AT 0 Be able to do problems calculating the heat involved in temperature changes or the temperature change resulting from the addition or loss of heat
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