Chapter 6 Notes
Chapter 6 Notes General Chemistry 0110
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This 4 page Class Notes was uploaded by Grace Lee on Wednesday March 11, 2015. The Class Notes belongs to General Chemistry 0110 at University of Pittsburgh taught by in Fall2014. Since its upload, it has received 145 views. For similar materials see General Chemistry 1 in Chemistry at University of Pittsburgh.
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Date Created: 03/11/15
General Chemistry 110 Chapter 6 Notes Thermodynamics science of relationships between heat and other forms of energy A Energy and its Units a Energy potential or capacity to move matter property of matter i Different forms are interconverted b Kinetic Energy energy associated with an object by virtue of its motion i E 12mvquot2 ii KE depends on both mass and speed iii SI unit of energy kg x mquot2squot2 iv Joule SI unit of energy c Calorie cal non SI unit of energy commonly used by chemists originally de ned as the amount of energy required to raise the temperature of one gram of water by one degree Celsius i 1 cal 4184 Joules d Potential Energy energy an object has by virtue of its position in a eld of force i E mgh e Internal Energy sum of kinetic and potential energies of particles making up a substance i E total KE PE U 1 U is internal energy f Law of conservation of energy energy may be concerted from one form to another but total quantity of energy remains constant i Conserved B First Law of Thermodynamics Work and Heat a Thermodynamic System substance or mixture of substances that we single out for study in which a change occurs b Surroundings everything in the vicinity of the thermodynamic system c Work energy transfer energy ow into or out of a thermodynamic system whose effect on the surroundings is equivalent to moving an object through a eld of force i W is positive when work is done on system ii W is negative when work is done by system d Heat q energy transfer into or out of a thermodynamic system that results from a temperature difference between the system and its surroundings e f g i Flows as long as system and surrounding in contact equilibrium ii Absolute temperature of a gas is directly proportional to average kinetic energy 1 Add heat l increase internal energy 2 Increase in internal energy means energy distributed over molecules in sample depends on size of gas sample 3 System absorbs heat energy added 4 System evolves heat energy taken away Change in internal energy extensive property depends on amount of substance in system State function property of a system that depends only on its present state which is determined by variables such as temperature and pressure and which is independent of any previous history of the system First law of Thermodynamics change in internal energy of a system U equals qw heat plus work C Heat of Reaction Enthalpy of Reaction a an Heat of reaction heat q is absorbed or evolved from a reaction system to retain a xed temperature of the system under the conditions speci ed for the reaction i Exothermic Process chemical reaction or a physical change in which heat is evolved q is nega ve ii Endothermic Process chemical reaction or physical change in which heat is absorbed q is positive Pressurevolume work w negative of the pressure times the change in volume of system i W PV ii Negative because w is de ned from perspective of system iii Positive when system expands and does work on surroundings loses energy w F x h PA x VA PV Enthalpy internal energy plus pressure times volume I HUPV Enthalpy of Reaction change in enthalpy delta h for a reaction at a given temperature and xed pressure Thermochemical equation chemical equation for a reaction in which the equation is given a molar interpretation and the enthalpy of reaction for these molar amounts is written directly after the equation i When a thermochemical equation is multiplied by any factor the value of delta H for the new equation is obtained by multiplying the value of H in the original equation by same factor ii When a chemical equation is reversed the value of delta H is reversed in sign D Applying Stoichiometry to Heats of Reaction a Convert grams to molar mass of A then K per mole in reaction to heat E Measuring Heats of Reaction a Heat Capacity quantity of heat needed to raise the temperature of the sample of substance one degree Celsius or one Kelvin L qCt ii Heat capacity directly proportional to amount of substance 1 Molar Heat capacity of substance is heat capacity of one mole Speci c Heat Capacity quantity of heat required to raise temperature of one gram of a substance by one degree Celsius at constant pressure i Q s x m x t Calorimeter device used to measure the heat absorbed or evolved during a physical or chemical change i Heat of reaction in constantpressure calorimeter equals enthalpy of reaction F Hess s Law a Hess39s law of heat summation for a chemical equation that can be written as the sum of two or more steps the enthalpy change for the overall equation equals the sum of the enthalpy changes for the individual steps i Enthalpy change for overall chemical change is the same ii Multiply by coefficients and cancel out G Standard Enthalpies of Formation a b C d Standard State standard thermodynamic conditions chosen for substances when listing or comparing thermodynamic data 1 atm pressure and the speci ed temp of 25C Delta H standard enthalpy formation i Elements exist in different states Allotrope one of two or more distinct forms of an element in same physical state Reference Form stablest form physical state and allotrope of the element under standard thermodynamic conditions e Standard enthalpy of formation Standard Heat of formation enthalpy change for the formation of one mole o the substance in its standard state from its elements in their reference form and in their standard states i Use table to standard enthalpies of formation ii Delta H sumn coefficient of product summ coefficient of reactant f Enthalpies of formation can be de ned for ions H Fuels foods commercial foods and rocket fuels a Fuel any substance that is burned or similarly reacted to provide heat and other energy i Supply substances for growth and repair of tissue substances for synthesis of compounds in regulation of body and energy b Same process as combustion c Fats contain more than twice the fuel per gram as carbs
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