4d Flashcards
what is entropy a function of
entropy is a function of state
Sa and Sb relate to what
they relate to different states
when Sa and Sb are plotted on a graph,, what are the axis
u have volume on the Y
and temperature on the X
what does Sb - Sa equal
difference in entropy
dS = dQ/T
is dQ and sQ state functions
nopeee
to think of Q.
u need to do dS = dQ/T
how to make heat a state functio, q or Q
we add temperature to the mix!!
so dS = dQ / T
what does dQ/T equal if the process is reversible
if dQ/T is reversible it will equal 0.
aka it makes a complete circle and the reaction starts and ends at the same point.
so tbh we dont rlly know if the reation occured or not.
what will dQ/T equal if the process is irreversible
if its irreversible dQ/T will be smaller than 0.
we would be able to see that the reaction took place bc it doesnt start and end at the same time
dQ/T (aka change in entropy) when the process is reversible =
0
dQ/T is the process is irreversible
< 0
smaller than 0.
for a system in an environment: entropy change of the system will be
smaller or equal to 0
aka dQ/T < 0 or equal to
for a system in an environment: entropy change of theenvironment will be
> 0
equal to 0 or positive.
in areversible reaction.. what is hard to clock
its hard to clock if the reaction actually took place.
bc dS aka dQ/T is equal to 0.
so if change is 0,, how do we know if anything actually happened.
in an irreversible system,, what is dS and what is dQ/T
dS is 0. meaning it starts and ends at the same entropy level.
dQ/T < 0 : this is change in heat exchange: which can tell us if a process has occured bc it doesnt start and end at 0.
dQ/T < 0
in an irreversible reaction,, dS = 0,, so we cant tell if a reaction takes place,, but what can we use to tell if it takes place and what equation is it
dS = 0
but yk what doesnt equal to 0.
dQ/T aka heat exchange does not equal to 0.
dQ/T < 0 !!!!
so we can use it to see if smt has acc happened.
e is used for what
to tell us were talking about the environment
what does i tell us about
tells us were talking about the internal
diS corresonds to the irreversible part which equals to
not zeroooooo
dis stands for what
internal entropy change
which doesnt equal to 0
and is the irreversible part
dS = what in terms of i and e
dS = diS + deS = 0
e =
exchange of matter and energy
entropy difference of the system
i =
entropy change related to irreversible processes within the system
diS goes from being smaller than what,,, to being bigger than what when introducing an irreversible process
diS goes from being smaller than 0
to being larger than 0
when introducing an irreversible system
what isnt exchanged in a closed system
no matter exchange.
deS = dQ/T
id diS is smaller than 0 ,, what must deS be
deS must be bigger than 0.
so if dS is equal to 0,, and diS is smaller than 0,, what must deS be
deS must be bigger than 0.
e for enormous,, aka larger than 0.
diS = incey wincey = small so smaller than 0.
diS is smaller or larger than 0
diS is smaller than 0
deS is smaller or larger than 0
deS is larger than 0
deS anddiS must do what to eachother
they should cancel eachother out
bc dS needs to be 0.
okay so in an irreverisble read=ction,, normall dS is equal to what
normal dS needs to be < dQ/T
but in an irreversible reaction §dS = what
§dS = 0
reversible reactionnnn:
dS =
§dS =
dS = dQ/T
§dS = §dQ/T = 0
in an irreverible reaction
dS =
§dS = 0
§dQ/T =
dS < dQ/T
§dS = 0
§dQ/T < 0
so if §deS = §dQ/T < 0 what does this mean
- for a system to return to its initial state
the entropy generated by irreversible processes within the system
heat must be exchanged to the exterior, increasing the entropy of the exterior
every process in nature does what
every process in nature increases entropy
what cool thing does entropy let us do
it lets us distinguish the past from the future
it can thereore help us predict the direction in which a system will evolve. direction of the process // reaction
so even if the reaction is reverisble,, it leaves a trace on the env,, so we can see the direction and acc realise if a reaction has occured or not.
what reaction is the cool one that tells us that entropy change can tell us if a reversible reaction has occured.
§deS = §dQ/T = < 0
1st law is what,, and what is the equation
1st law is conservation of energy
dU (closed system) = dQ + dw
if dS of a closed system is 0,, what does this mean
it means that the reaction is reverisble.
dS = whatttttt
dQ/T
dU in terms of temp, entropy and work
dU = TdS + dW
dU in terms of T , S , p and v
dU = TdS - pdV
what is entropy + can we use it to predict the direction of a reaction
every process increases entropy// so there must be something favourable about it
measure of disorder.
and lowkey everything loves disorder soooo
what did boltzman do
boltzman associated entropy with disorder + probability
entropy,, disorder,, probability.
S aka entropy is proportionate to whattt
ln( W)
which is the number of microstates
based on observation so no need for the super hardcore science stuff.
S in terms of boltzman
S = kB x ln(W)
entropy = boltzman constant x ln( W )
W being the number of microstates.
what remains constant in an adiabatic process
temperature remains the same in an adiabatic process!!
it means temp constant
when were thinking of S = KB x ln(w) what should we always think offff
think of a box with a barrier,, in the middle
with amount of dots in each side of the box on opp sides of the barrier!!!!!!!
in the boltzman box,, S = kb x ln(w)
what does N mean
N is the number of particles of gas on each side of the box,, on each side of the barrier.
N1 + N2. = what
N
aka N 1 = number of gas particles on one side of the boltzman box
N2 = number of particles on the other side of the boltzman box
the barrier in the boltzman box is
its permeable so an equilibrium can be met bc particles can move to opp sides of the box.
what do we need to try and max out
we want to max out S of the boltzman entropy thing
so we want to max out W. the number of microstates.
so we need to balance the number of particles on each side of the box!!!
what is W
( N1 + N2) ! // N1! N2!
so kinda like reduced mass but u add the ! to it.
a symmetric distribution of particles in the boltzman distribution is what
its wantedddd
bc it maxes out W
which maxes out S.
which is what we want
bc W = (N1 + N2)! // N1! N2!
microstates with a larger W are what
theyre more probable
if the distribution is asymmetrical,, W is reduced which means what else is redued
it means that the equilibrium state is also reduced.
the boltzman box this only occurs in what type of reaction
a irreversible entropy increase
it doesnt work in a reversible reaction bc if u want to max out W and there fore the equilibrium state and S.
once youve finally got a symmetric distribution,, why would u want to reverse that and get an asymmetric distributio again?/
the distribution that corresponds to the equilibrium is what one
the one that maxes out W and therefore S.
aka the one with the most symmetric distribution.
bc S = Kb x ln(w)
what leaves a trace on the environment in a reversible reaction
entropyyyyyy. the past and present thing we were one about to see if a reaction acc took place.
what can we use S to do
S can be used to predict the direction of a reaction.
if we have a box,, lhs and rha = what
lhs = T1
rhs = T2
T1 would be larger than T2,, meaning there is heat flux from T1 to T2 aka from the lhs to the rhs.
making dQ positive ,, making diS > 0 .
diS thereofre isss
-dQ/T1 + dQ/T2
= ( - 1/T1 + 1/T2) dQ
so diS / dT =
(-1/T1 + 1/T2) dQ/dT
meaning S depends on diff in temp!!!!
chnage in S /T
when heat flux occurs,, heat is moved from high temp to low temp,, soon the equilibrium will be established and the temp change will be 0 ,, when this occurs what happens
the rate of S will vanish and we reach the minimum equilibrium state.
plot of rate of exchange : diS/dT ,, with T1-T2 on the axis.
> 0
at equilibrium the rate function will be
at the minnnnn
aka when T1 is hotter than T2 meaning their difference is (+) and thereofore above 0.
rate of exchange is at its min.
smiley face smile
graph when S is plotted against (T1 - T2)
maxxxxxx
hill shape!!!
when the temp difference is largeu gettt
maxxx
when temp diff is small u get
minnnnn
rate =
entropy =
= min
= max
the thing that maximises the states corresponds to theee
equilibrium
non eq to equilibrium
how does W and S work
W ne < W
S ne < Se
so we want equilibrium!!!!
