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
quantities of systems
macrostate and microstate
macrostate system
temperature, pressure, volume
AKA collection of microstate
microstate system
kinetic energy, force, velocity
macrostate at equilibrium
does not change over time
microstates can be specified at anytime
entropy in the concept of system
(S) no. microstates of system
nr of microstates at given total energy
W(E)
W entropy
omega
Boltzmann contrast
Kb = 1.38064852*10 to power -23 m2kgS-2k-1
entropy equation
S = Kb*In(W)
consequences of increasing no. particles(N)
using binomial distribution
equation of particles binomial distribution - P(N,NL)
N!/ (N-NL)!NL! *1/2N
nature of equilibrium width in graph
width of distribution =total no. macrostates
gets narrower with around 1/sq root(N)
increase in size of system
better defined equilibrium value
example of 2 boxes and 4 particles on one side and when open how many will go to the other side
(labelling)
system - 2 boxes
macrostate - NL no.particles on left
microstate - W(4,NL) particular configuration of 4 particles in system
example of 2 boxes and 4 particles on one side and when open how many will go to the other side (method)
- no. particles in NL (0,1,2,3,4)
- W(4,NL) - binomial distribution
- divide W(4,NL) by W(total)
example of 2 boxes and 4 particles on one side and when open how many will go to the other side (total)
total microstate 16 - W(total)
able to be plotted on a graph( bar chart)
