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35 Cards in this Set

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first of thermodynamics
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
endothermic
absorb heat from warmer sys to cooler system
exothermic
release heat from warmer sys to cooler system
heat
q= mcT(f-i)

c=specific heat

measured in the same unit as energy
(calories or joules)
entropy (S)
measure of the disorder or randomness of a system

greater the disorder = inc in entropy

state function
Dealta S = Sfinal - Sinitial
entropy btw phases
gas>liquid>solid
delta S (state function)
dealta S = q/T

q = heat added to a sys
Second law of thermodynamics
all spontaneous processesin an isolated system lead to inc in entropy
delta S universe
= delta Ssys + delta Ssurrounding >0
Enthalpy (H)
heat content of a system

heat change at constant P
delta H
= Activation E foward - activation E reverse

=Eproduct -Ereactant

=Hproduct-Hreactant

equal to the heat absorbed or evolved by the systme at constant P
delta H = +
endothermic
delta H = -
exothermic
standard heat of formation

delta Hf
at STP (1atm, 273K)
standard head of rxn
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)
Hess law
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
bond dissociation energy
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
Gibbs Free Energy (G)
=dH-TdS
describe overall spontaneity of a exn

represents maximum energy of enery released by a process occuring at STP
dG = -
rxn is spontaneous
dG = +
rxn is not spontaneous
dG = 0
equalibrium

and dH=TdS
dH = -
dS = +
spontaneous at all temp
dH = +
dS = -
nonspontaneous at all temp
dH = +
dS = +
spontaneous only at high temp
dH = -
dS = -
spontaneous at low temp
dGrxn
= (sum of dGf of product)-
(sum of dGf of reactant)
conduction
heat transfered directly through vibration of atoms and molecule of materials
radiation
E transfered via electromagnetic waves

no medium, occur in vaccum
convection
transfered by the bulk movement of fluids, known as convection current

warm air rise and cool air falls due to difference in density
when system can't exchange energy or matter with the surrounding as with an insulated bomb reactor
isolated system
when system cannot exchange energy but not matter with the surrounding, as with steam radiator
closed system
when syste can exchange both matter and energy with the surrounding as with pot of boiling water
open system
isothermal
constant temp
adiabatic
no heat exchange occur
isobaric
pressure of the system remains constant