Details Title: 14B Thermodynamics Description: Scerri's reader Total Flash Cards: 46 Created: 04/29/2008 16:24:13		New Users: To study from this flashcard set, or to create your own your own study flash cards, REGISTER HERE. Existing Users: CLICK HERE. Additional Chemistry Flashcards
Cards in this set: Term thermodynamics Definition the study of heat and energy Term mechanical equivalent of heat Definition calorie -> energy Term what is heat? Definition not a mechanical object but a mechanism for the transfer of energy Term electrical current Definition flows if there is a difference in electrical potential Term heat flows Definition if there is a difference in thermal potential (thermal energy) Term chemical reactions occur Definition if there is a difference in chemical potential [dG] Term intensive property Definition independent of quantity [T,P, ...] Term extensive property Definition scales with quantity [E,V,mass] Term E=3/2 RT Definition for 1 mole of ideal gas Term Energy remains constant Definition provided that temp remains constant Term 1st law of thermo Definition energy is neither created nor destroyed but only redistributed as heat or work. dE = q + w Term How is constant Temp maintained? Definition Only if the heat entering the system is equal to the work done by he system Term what does dE not depend on? Definition How the change in E is made. [fast/slow] Term gradual change allows Definition the system to remain in equilibrium. It ensures that Pext = Psys Term state functions Definition energy, entropy, enthalpy, free energy Term entropy macroscopic equation Definition dS = qrev/T Term 1st law can be applied to different experimental conditions - Definition 1. expansion or contraction at fixed P [dE=q-PdV] 2. if V is kept constant during some change in T or P or both [dE = q at constant V] Term Hess' Law Definition the enthalpy change for the direct process is equal to the sum of the enthalpy changes for all the indirect steps Term what direction does a spontaneous process occur Definition the direction that maximizes the associated number of microstates Term how can crystals exist if nature favors high disorder? Definition By minimizing energy through interatomic/intermolecular forces. There is a balance between minimizing energy and maximizing disorder. Term S = S1 + S2 Definition entropy is an extensive property which must increase as the sum of the entropies of two or more systems Term W = W1 x W2 Definition the number of microstates of the combined system must be given by the product of the number of microstates of the systems. Term why is dS>= q/T Definition q is less then q reversible because more work is done when the process is reversible Term phase changes Definition we are at equilibrium so we have reversibility Term phase changes Definition we are at equilibrium so we have reversibility Term change in enthalpy Definition q at constant pressure Term 2nd law of thermo Definition entropy increases until a maximum is reached when equilibrium is attained Term spontaneous change and entropy of the universe Definition spontaneous change occurs only if the entropy of the universe increases Term dH - and dS + Definition always spontaneous Term dH + and dS - Definition never spontaneous Term dH and dS + Definition spontaenous at high temperature Term dH and dS - Definition spontaneous at low temp Term steric factor Definition p, denotes the fraction of molecules with correct orientation Term frequency factor Definition z, maximum rate of reactin cannot exceed frequency of collisions Term entropy increases why does dG decrease Definition dG =-TdS -- connected to dSuniv and the second law Term relationship between Go and K Definition dGo=-RTlnK dG - k>1 products dG + k<1 reactants Term 3rd law of thermo Definition the entropy of any pure substance approaches 0 at the absolute zero of temperature. the entropy of any pure substance is assumed to be zero at 0K Term speed of a rxn depends on Definition 1. number of collisions/sec 2. energy/collision 3. proper orientation Term 3 conditions for a succesful rxn Definition 1. collision must occur 2. collisions must possess a minimum Ea 3. correct orientations must exist Term # of collisions/sec Definition maximized by high concenrations Term energy per collision Definition due to high temps Term proper orientation Definition governed by state of matter Term dependence of rate on concentrations Definition in general, the greater the conc of a substance, the larger the rate of rxn Term ex of 1st order process Definition radio active decay Term what is rate determined by Definition # of correctly oriented particles (a) and Ea Term catalyst Definition a catalyst increases the rate of reaction but not the yield, is not changed in the course of a reaction