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35 Cards in this Set
- Front
- Back
first of thermodynamics
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expression of the universal law of conservation of energy, and identifies heat transfer as a form of energy transfer.
The increase in the internal energy of a thermodynamic system is equal to the amount of heat energy added to the system minus the work done by the system on the surroundings. dU = Q-W du = inc in the internal enery of system by James Prescott Joule |
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endothermic
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absorb heat from warmer sys to cooler system
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exothermic
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release heat from warmer sys to cooler system
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heat
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q= mcT(f-i)
c=specific heat measured in the same unit as energy (calories or joules) |
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entropy (S)
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measure of the disorder or randomness of a system
greater the disorder = inc in entropy state function Dealta S = Sfinal - Sinitial |
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entropy btw phases
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gas>liquid>solid
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delta S (state function)
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dealta S = q/T
q = heat added to a sys |
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Second law of thermodynamics
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all spontaneous processesin an isolated system lead to inc in entropy
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delta S universe
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= delta Ssys + delta Ssurrounding >0
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Enthalpy (H)
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heat content of a system
heat change at constant P |
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delta H
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= Activation E foward - activation E reverse
=Eproduct -Ereactant =Hproduct-Hreactant equal to the heat absorbed or evolved by the systme at constant P |
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delta H = +
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endothermic
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delta H = -
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exothermic
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standard heat of formation
delta Hf |
at STP (1atm, 273K)
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standard head of rxn
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the hypotheical enthalpy change that would occur if the exn were carried out under standard conditions
=(sum of del Hf of product) - (sum of del Hf of reactant) |
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Hess law
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states that if rxn can be broken down into a series of steps the enthahpy change for the overall net reaction is just the sum of the enthalpies ofeach step
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bond dissociation energy
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average of the engergy required to break a particular type of bond in one mole of gaseous molecules
deltal H rxn = (H of vond broken)+(H of bonds formed or = energy input - energy output |
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Gibbs Free Energy (G)
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=dH-TdS
describe overall spontaneity of a exn represents maximum energy of enery released by a process occuring at STP |
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dG = -
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rxn is spontaneous
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dG = +
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rxn is not spontaneous
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dG = 0
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equalibrium
and dH=TdS |
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dH = -
dS = + |
spontaneous at all temp
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dH = +
dS = - |
nonspontaneous at all temp
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dH = +
dS = + |
spontaneous only at high temp
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dH = -
dS = - |
spontaneous at low temp
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dGrxn
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= (sum of dGf of product)-
(sum of dGf of reactant) |
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conduction
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heat transfered directly through vibration of atoms and molecule of materials
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radiation
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E transfered via electromagnetic waves
no medium, occur in vaccum |
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convection
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transfered by the bulk movement of fluids, known as convection current
warm air rise and cool air falls due to difference in density |
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when system can't exchange energy or matter with the surrounding as with an insulated bomb reactor
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isolated system
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when system cannot exchange energy but not matter with the surrounding, as with steam radiator
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closed system
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when syste can exchange both matter and energy with the surrounding as with pot of boiling water
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open system
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isothermal
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constant temp
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adiabatic
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no heat exchange occur
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isobaric
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pressure of the system remains constant
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