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Classify each process by its individual effect on the entropy of the universe, S.

Drag the appropriate items to their respective bins: Increases S of the Universe; Does not Affect S of the Universe; Decreases S of the Universe.

• a process run infinitesimally slowly at equilibrium and reversed to its original state
• a constant composition mixture of solid and liquid water at STP (273.15 K and 1 atm)
• motion of a frictionless pendulum
• a bag of red marbles and a bag of green marbles dumped together on a table top
• ice melting to water above the melting point
• sublimation of naphthalene (mothballs)

## Answer

Entropy means disorder. Suppose random ness of the molecules increases, then entropy increases. Entropy (with the symbol S) in thermodynamics indicates the degree of system disorder Entropy, like other thermodynamic terms, can only be calculated from the initial and final changes.

The processes below have no effect on the entropy of the universe:

1. A process run infinitesimally gradually at equilibrium and reversed to its original state.
2. A constant composition mixture of solid and liquid water at standard temperature and pressure.
3. The motion of a frictionless pendulum.

Increases S of the Universe:

1. A bag of red marbles and a bag of green marbles dumped together on a table top.
2. Ice melting to water above the melting point.
3. Sublimation of naphthalene (mothballs)
Which of the following is true of the internal energy of the system and its surroundings following a process in which ΔEsys=+65kJ.
Which of the following is true of the internal energy of the system and its surroundings following a process in which .
The system and the surroundings both lose 65kJ of energy.
The system and the surroundings both gain 65kJ of energy.
The system gains 65kJ of energy and the surroundings lose 65kJ of energy.
The system loses 65kJ of energy and the surroundings gain 65kJ of energy.
The system gains 65kJ of energy and the surroundings lose 65kJ of energy.
Part A Part complete
The law of ________ states that energy that can be neither created or destroyed.potential energy
the conservation of energy
thermochemistry
the consecration of energy
kinetic energy
the conservation of energy
Which of the following statements about energy is FALSE?
Energy can be converted from one type to another.
Systems tend to change in order to lower their potential energy.
Kinetic energy is the energy associated with its position or composition.
Energy is the capacity to do work.
Kinetic energy is the energy associated with its position or composition
Identify the process that is spontaneous
Identify the process that is spontaneous
electrolysis
burning gasoline
photosynthesis
water flowing uphill
rusting of iron
rusting of iron
All of the following are examples of a spontaneous process except
All of the following are examples of a spontaneous process except
a reaction speeding up upon the addition of a catalyst.
a nail left outside in the rain starts to rust.
a book falls off a desk and drops on the floor.
water freezing when the temperature drops below 0°C.
a boulder slides down the side of a mountain.
a reaction speeding up upon the addition of a catalyst.
Which of the following is true?
Which of the following is true?
A spontaneous reaction is always a fast reaction.
A spontaneous reaction is always a slow reaction.
The spontaneity of a reaction is not necessarily related to the speed of a reaction.
The spontaneity of a reaction is not necessarily related to the speed of a reaction
In which of the following processes does the substance become more orderly?
In which of the following processes does the substance become more orderly?
salt dissolving in water
water freezing
dry ice subliming
ice melting
water evaporating
water freezing
J =
kg(m^2/s^2)
When Delta E > 0
endothermic, heat absorbed
When Delta E < 0
exothermic, heat released
Delta E =

E final – E initial

q + w
where q = mCdeltaT
C = heat capactity, specific heat
=nDeltaH
w = work (-PdeltaV)

1st law of thermodynamics
“Law of concentration of energy”
energy is neither created nor destroyed, only converted into another form
Delta E of universe =
0
Delta E system + Delta E surroundings
Delta E system =
-Delta E surroundings
change in volume quantifies ..
work
you can begin to quantify energy by
how random it is
Spontaneous process:
process that occurs with out any ONGOING input of energy ( a rxn will just go, may require EA)
most spontaneous processes are … due to …
exothermic
delta E final > delta E initial
Entropy:
S
(# of states possible)
a measure of chaosA quantity that is the driving force behind chemical and physical change in the world
2 particles with 2 quanta of energy, what are the possible arrangements
A**B A*B* AB**
3 possibilities of energy distribution
4 particles with 2 quanta of energy, what are the possible arrangements
A**BCD A*B*CD A*BC*D A*BCD*
AB**CD AB*C*D AB*CD* A*BCD*
ABC**D ABC*D*
ABCD**10 posibilities
S =

Kb*Ln*W

Kb = 1.38 *10^-23 (J/K) “Boltzman constant”
W = # of ways you can write energy distributions (# of probabilities)

Delta S =

KbLn(Wfinal/Winitial)

Qrev / T (for a reversible process of using Qrev at an irreversible T)

nRln(v2/v1)

calc change in S from 2 particles with 2 quanta energy to 4 particles with 2 quanta energy
DeltaS = KbLn(Wfinal/wInitial)
DeltaS= (1.38 * 10^-23)*Ln(10/3)
Delta S = 1.66*10^-23 (J/K)
2nd Law of thermodynamics
for a spontaneous process deltaS universe > 0
“energy spreads out”
“entropy of the universe is always increasing”
“you can’t win the game or break even”
3rd law of thermodynamics
S = 0 at 0 K for perfect crystal
b/c S = KbLn(1) = 0 (J/K)
The entropy …… during the phase change of solid to liquid is ……
increase
much smaller than the entropy increase during the phase change from liquid to gas
E =
energy
(3/2)nRt
in the rxn 2 N20(g) -> 2 N2 (g) + O2 (g)
products are …
more chaotic than reactants because 2 things become 3 things
in general deltaSrxn > 0 when
1) delta n = nproducts – nreactants
delta n > 0 (if more product than reactanant)
2) s -> l
3) l -> g
4) s -> g
5) when delta V > 0
Delta S rxn =
Qrev/T
H20 (s) -> H20 (l) at 25 C deltaH fusion = 6010 (J/mol)
@ 0C
@ 25C
@ – 10 C
@ 0C
DeltaSrxn = Qrev/T
if delta H = (q/n), q = ndeltaH * assume a mol
deltaSrxn = (nDeltaHrev/T) = ((1 mol)(6010 J/mol))/(273k) = 22.0 (K/J)
this is a reversible [email protected] 25 C
we measure deltaHsurr
that is 1st law deltaEuniverse = 0
qsys = – qsurr
deltaSsurr = (qrev/T) = (qsys/T)
deltaSsurr = (qsurr/T) = (-qsys/T)
deltaSsurr = -(6010 J/mol)( 1 mol) / (298 k)
deltaSuniv = detaSsys + deltaSsurr
deltaSuniv = (22.0 j/k) + (20.2 J/K)
deltaSuniv = 1.8 J/K
2nd law
deltaSuniv > 0 therefor this is a spontaneous [email protected] C
deltasys = qsys/T = (6010 J/mol)/(273K) = 22 J/K at rev temp
deltaSsurr = -qsys/T = (-6010 J/mol)/(263k) = -22.9 j/k
deltaSuniv = deltaSsys + deltaSsurr = (22.0j/k) + (-22.9 j/k) = -0.9 j/k
delta S univ < 0 there for not spontanrous b/c 2nd law

1.0 L of gas at 298 K, 1.0 atm expands isothermally to 2.0 L. what is the entropy change of the system?
DeltaS = nRtLn (v2/v1)
PV = nRt
n = (PV)/(RT) = ((1.0 atm) * (1.0 L))/((0.082057 l*atm/mol*K)(298 K)
n = 4.46*10^-2 mol
deltas = nRtln(V2/v1) = (4.46 * 10 ^-2 mol)(8.3145 J/molK)ln(2.0L/1.0L) = 0.257 J/K
DeltaSuniverse =
deltaSsys + deltaSsurr
qrxn/T + -qrxn/T
(for a revT) (at a temp given)
deltaSsys – (deltaHsys/T)
S* STP [ ] =
1 M
deltaS* =
= S*products – S*reactants
Calc the delta Srxn for the rxn
CO (g) + 2H2 (g) -> CH3OH (l) @ STP
pg 2 notes
delta Ssurr =
Qsurr/T
Qsurr =
-qsys
what is the deltaH*rxn for
CO (g) + 2H2 (g) -> CH3OH (l) @ STP
pg 3 notes
is the rxn CO (g) + 2H2 (g) -> CH3OH (l) @ STP spontaneous?
pg 3 notes
is the rxn C12H22O11 (S) + 12O (g) -> 12 CO2 (g) +11 H2O (g) @ 37C 1 atm
pg 3 and 4 of notes
deltaH*rxn =
deltaH*products-deltaH*reactants

Consider a system consisting of a cylinder with a movable piston containing 106 gas molecules at 298 K at a volume of 1 L. Consider the following descriptions of this system:

A. Initial system, as stated in the problem statement.

B. Starting from the initial system, the volume of the container is changed to 2 L and the temperature to 395 K.

C. Starting from the initial system, a combination reaction occurs at constant volume and temperature.

D. Starting from the initial system, the gas reacts completely to produce 107 gas molecules at 395 K in a volume of 2 L.

E. Starting from the initial system, the temperature is changed to 395 K at constant volume.

Arrange the descriptions in order of increasing number of microstates in the resulting system.

A. You should relate microstates and entropy here. Increasing microstate will increase entropy. Also increasing temperature and volume increase entropy. So you can think that increasing temperature and volume will create more microstates.

The order is D>B>E>A>C.

A gaseous system undergoes a change in temperature and volume. What is the entropy change for a particle in this system if the final number of microstates is 0.749 times that of the initial number of microstates?

Entropy of the system is:

S = k ln(W) …… W is the number of microstates available to the system.

S2 -S1 = kln W2 – klnW1

dS = k ln (W2/W1)

= 1.38*10-23 ln 0.749

= -3.99 * 10-24 J/(K*particles)

Rank these systems in order of decreasing entropy.

Rank from highest to lowest entropy. To rank items as equivalent, overlap them.

A) 1 mol carbon tetrafluoride gas at 273k 40L

B) 1 mol krypton gas at 273K 40L

C) 1/2 mol krypton gas at 100k 20L

D) 1 mol krypton gas at 273K 20L

E) 1/2 mol krypton liquid at 100K

F) 1 mol fluorine gas 273 K 40L

G) 1/2 mol krypton gas at 273K 20L

Thank you! Can you also provide an explanation how to figure it out?

1. The entropy is degree of disorderness, higher the disorderness higher the entropy.

2. If two gas have same number of moles, then the gas with more number of atoms in a molecule will have higher entropy ( due to more number of macrostates)

3. The smaller the volume the less the molecules can move around which also reduces the number of possible different states and hence less the entropy

4.In a colder gas the molecules or atoms are not so energetic and so do not occupy so many different energetic states and hence will have less entropy .

5. A liquid is more ordered than a gas, reducing its entropy.

So the order will be :

A > F > B> D > G > C > E

Classify each process by its individual effect on the entropy of the universe, S.

Drag the appropriate items to their respective bins: Increases S of the Universe, Does not Affect S of the Universe, Decreases S of the Universe.

a process run infinitesimally slowly at equilibrium and reversed to its original state

a constant composition mixture of solid and liquid water at STP (273.15 K and 1 atm)

motion of a frictionless pendulum

a bag of red marbles and a bag of green marbles dumped together on a table top

ice melting to water above the melting point

sublimation of naphthalene
(mothballs)

Does not Affect S of the Universe

a process run infinitesimally slowly at equilibrium and reversed to its original state

a constant composition mixture of solid and liquid water at STP (273.15 K and 1 atm)

motion of a frictionless pendulum

Increases S of the Universe

a bag of red marbles and a bag of green marbles dumped together on a table top

ice melting to water above the melting point

sublimation of naphthalene

Explanation :

Entropy means diorder. if random ness of the molecules increasesm then entropy increases.

Calculate S* rxn for the following reaction. The S* for each species is shown below the reaction.

C2H2(g) + 2 H2 (g) ————–> C2H6(g)

S*(J/mol x K) for C2H2(g) = 200.9 , for 2H2 = 130.7, and for C2H6 = 229.2

We know,

DeltaSreac = DeltaS products- DeltaS reactants

Given,

S*(J/mol x K) for C2H2(g) = 200.9 , for 2H2 = 130.7, and for C2H6 = 229.2

So,

DeltaS reac = 229.2- 200.9 – (130.7×2)

= – 233.1 J/mol.K

dispersion is
the spreading out of energy
a catalyst can __________ but cannot ________
speed up
make a nonspontaneous rxn spontaneous
a nonspotaneous process is made possible by
coupling it to another process that is spontaneous or by supplying it energy from an external source.
kinetics has to do with
speed of rxn
most spontaneous processes are …
exothermic
macrostate
the state of the system
microstate
the exact internal energy distribution among the particles at any one given instant
enthalpy
a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
a chemical rxn will precede in the direction …
that increases that entropy of the universe
the higher the temperature…

the lower the amount of energy for a given amount is dispersed

(J/K)

the differences in entropy between the phases
is the number of energy equivalent ways of arranging the particles in each state. (more in gas, least in solid)
the energy in a molecular solid consists largely of
the vibrations between its molecules
the energy in a molecular solid consists largely of
straight line motions of the molecules (called transnational energy)
and rotations of the molecules (rotational energy)
entropy increases (_____) for each of the following :

deltaS > 0

the transition from a solid to a liquid
the transition from a solid to a gas
the transition from a liquid to a gas
an increase in the number of the moles of a gas during a chemical reaction

predict the sign for delta S for each
A) H2O (g) -> H2O (l)
B) solid carbon dioxide sublimes
C) 2 N2O (g) -> 2N (g) + O2 (g)
Definitions of standard states for
A gas
A liquid or solid
Substance in solution
The more massive a molecule the ___ its entropy
Great
The effect of a state change on S is _____ than the effect of molar mass
Far greater
Allotropes
Different forms of the same element
In Allotropes the _______ structure results in
Less constrained
More places to put energy and therefore greater entropy compared to diamond
For a given state of matter entropy generally ____ with increasing molecular complexity
Increases
dissolution of a crystalline solid into solution usually results in ____ entropy
Increasing
Arrange SO3, Kr, Cl2 in order of increasing standard molar entropy
Factors affecting entropy
Calc deltaS*rxn for
4 NH3 (g) + 5 O2 (g) -> 4 NO (g) + 6 H2O (g)

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