2nd law of Thermodynamics and entropy Flashcards
2nd law of Thermodynamics
in isolated system, entropy can only increase
change of entropy
proportional to heat transferred from system to surroundings
change of entropy equation
DS>= Dq/T
Dq
change of heat (s)
T
temperature
change in entropy at equilibrium
DS=Dq/T
entropy equation depends inversely on temp
-DS=Dq/T
equation of entropy change of surroundings
DS(surr) = Dq(surr)/T
or -DS=DH(surr)/T (DH=Dq at constant pressure)
changes in exothermic reaction
entropy of system decreases
entropy of surroundings increases as energy is transferred out
changes in endothermic reaction
entropy of system increases
entropy of surroundings decreases as energy if transferred in
how to make a spontaneous reaction
total of entropy of system + surrounding must be >0
equation for a spontaneous reaction
DS(total) = DS(system) + DS(surr) >0
why does water freeze at -10 and not 10 degrees celsius
finding DS(surr) for each
temperature used in kelvin
DS(system) is -22Jk-1mol-1
find DS(total) and find which reaction occurs
Gibbs free Energy (DG)
energy from reaction that is available to generate work
equation for DG
DG = DH - TDS