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:

- A process run infinitesimally gradually at equilibrium and reversed to its original state.
- A constant composition mixture of solid and liquid water at standard temperature and pressure.
- The 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 (mothballs)

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 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

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.

Identify the process that is spontaneous

electrolysis

burning gasoline

photosynthesis

water flowing uphill

rusting of iron

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.

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.

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

E final – E initial

q + w

where q = mCdeltaT

C = heat capactity, specific heat

=nDeltaH

w = work (-PdeltaV)

energy is neither created nor destroyed, only converted into another form

Delta E system + Delta E surroundings

delta E final > delta E initial

(# of states possible)

a measure of chaosA quantity that is the driving force behind chemical and physical change in the world

3 possibilities of energy distribution

AB**CD AB*C*D AB*CD* A*BCD*

ABC**D ABC*D*

ABCD**10 posibilities

Kb*Ln*W

Kb = 1.38 *10^-23 (J/K) “Boltzman constant”

W = # of ways you can write energy distributions (# of probabilities)

KbLn(Wfinal/Winitial)

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

nRln(v2/v1)

DeltaS= (1.38 * 10^-23)*Ln(10/3)

Delta S = 1.66*10^-23 (J/K)

“energy spreads out”

“entropy of the universe is always increasing”

“you can’t win the game or break even”

b/c S = KbLn(1) = 0 (J/K)

much smaller than the entropy increase during the phase change from liquid to gas

(3/2)nRt

products are …

delta n > 0 (if more product than reactanant)

2) s -> l

3) l -> g

4) s -> g

5) when delta V > 0

@ 0C

@ 25C

@ – 10 C

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

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

qrxn/T + -qrxn/T

(for a revT) (at a temp given)

deltaSsys – (deltaHsys/T)

CO (g) + 2H2 (g) -> CH3OH (l) @ STP

CO (g) + 2H2 (g) -> CH3OH (l) @ STP

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.

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

make a nonspontaneous rxn spontaneous

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

(J/K)

and rotations of the molecules (rotational energy)

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

A) H2O (g) -> H2O (l)

B) solid carbon dioxide sublimes

C) 2 N2O (g) -> 2N (g) + O2 (g)

A gas

A liquid or solid

Substance in solution

More places to put energy and therefore greater entropy compared to diamond

4 NH3 (g) + 5 O2 (g) -> 4 NO (g) + 6 H2O (g)