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# EK Chem 3

### thermo

extensive properties properties that are proportional to the size of the system
intensive properties properties that are independent of the system
state function pathway independent, the state property going from 1 state to another is the same regardless how system was changed
heat movement of energy via conduction, convection, or radiation - always from hot to cold
convection thermal energy transfer via fluid movements
radiation thermal energy transfer via electromagnetic waves, related t T^4
conduction thermal energy transfer via molecular collisions - requires contact
PV work W = P*deltaV (constant pressure)`
1st law of thermodynamics energy of the system and surroundings is always conserved, any energy change must equal heat flow into system plus the work delta(E) = q + w (work on the system is positive)
2nd law of thermodynamics heat cannot be changed completely into work in a cyclical process entropy of isolated system will never decrease
carnot efficiency e = 1 - Tc/Th
internal energy collectve energy of molecules measured on a microscopic scale, often referred to as heat, thermal energy, state function
zeroth law of thermodynamics two bodies in thermal equilibrium share a thermodynamic property - which is a state function -- TEMPERATURE EXISTS
KEavg = =3/2*kT where k is Boltzman constant
enthalpy manmade property that accounts for extra capacity to to PV work, defined as H = U + PV, not conserved like energy, not constant (of the universe), state function
change in enthalpy at constant pressure delta(H) = delta(U) + P*delta(V)
standard enthalpy of formation change in enthalpy for rxn that creates 1 mole of a cmpd from raw elements in their standard state
if gas is not part of the rxn, the enthalpy change is... equal to the heat, which in the absense of work is equal to a change in energy
heat of rxn delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants)
Hess' law when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn
exothermic rxns have a positive or negative enthalpy negative
endothermic have a positive or negative enthalpy postive
if gas is not part of the rxn, the enthalpy change is... equal to the heat, which in the absense of work is equal to a change in energy
heat of rxn delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants)
Hess' law when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn
exothermic rxns have a positive or negative enthalpy negative
endothermic have a positive or negative enthalpy postive
if gas is not part of the rxn, the enthalpy change is... equal to the heat, which in the absense of work is equal to a change in energy
heat of rxn delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants)
Hess' law when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn
exothermic rxns have a positive or negative enthalpy negative
endothermic have a positive or negative enthalpy postive
if gas is not part of the rxn, the enthalpy change is... equal to the heat, which in the absense of work is equal to a change in energy
heat of rxn delta(Hrxn) = delta(Hf of products) - delta(Hf of reactants)
Hess' law when you add rxns, you can add their enthalpies; also, forward rxn = neg of reverse rxn
exothermic rxns have a positive or negative enthalpy negative
endothermic rxns have a positive or negative enthalpy positive
entropy nature's tendency to create the most probable situation that can occur w/in a situation, state f(x), extensivy property (increases w/ amt of substance)
delta(Suniverse) >=0 = delta(Ssystem) + delta(Ssurroundings)
entropy of system can decrease only if at the same time, the entropy of the surroundings increase by a greater or equal magnitude
ideal reactions create how much entropy change? zero - meaning they are reversible
if a rxn is unfavorable in terms of enthalpy, but increases entropy, will the rxn occur? yes, entropy is the driving force that dictates whether or not it will proceed
3rd law of thermodynamics assigns by convention a zero entropy value to any pure substance at absolute zero and in internal equilibrium
units of entropy? J/K
change in entropy related to heat eqn delta(S) = dqrev/T where dqrev is the infinitesimal change in heat per kelvin
Gibb's free energy delta(G) = delta(H) - T*delta(S) (all of the system not surroundings), extensive property, state function, represents maximum non-PV work available from rxn
when delta(G) is negative… the rxn is spontaneous
with +delta(H) and -delta(S), delta(G) will be.. positive
with -delta(H) and +delta(S), delta(G) will be… negative
what is value of gibb's free energy at equilibrium? zero
when both enthalpy and entropy are the same sign, free energy will be.. positive or negative, therefore spontaneity of rxn will depend on the temperature
Created by: miniangel918