chapter 16: spontaneous entropy Flashcards by Kisana Ngwenya

what is the first law of thermodynamics

energy cannot be created or destroyed
total energy of the Universe is constant
- 3. energy can be transferred

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what is the equation for
Euniverse

Euniverse= 0= Esystem + Esurroundings

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what is internal energy

the total energy in a system ( kinetic + potential)

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what is a spontaneous process?

a process that can proceed without any outside energy ( proceed on its own)

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what is a nonspontaneous process

requires energy to proceed

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if something is spontaneous in one direction, what will happen in the other direction?

if something is spontaneous in one direction then it will be nonspontaneous in the other direction

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what is an example of of a spontaneous process

nail rusting

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what is the spontaneous and nonspontaneous of melting and freezing in ice

above 0 degrees is spontaneous to melt
below 0 is spont. for ice to form

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does rate or speed affect spontaneity

no, a process can be spontaneous and slow

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what is the difference between thermodynamics and kinetics

thermodynamics tells us the DIRECTION and EXTENT of the rxn
Kinetics tells us the speed of the reaction

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when a piece of metal is heated to 150 degrees and added to water and the water gets hotter is that spontaneous or nonspontaneous

that is spontaneous because heat is flowing from high to low ( meaning no energy input)

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if a decompose H2O into H2 and O2

that is a nonspontaneus process because it takes energy to break them apart

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endothermic does not equal

nonspontaneous

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most spontaneous processes are what

exothermic but some are endothermic

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what are the two factors that are involved in spontaneous processes

decrease in the energy (enthalpy)
@ a constant temp, an increase in the disorder of a system ( entropy)

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what is the symbol for entropy

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what is entropy

the amount of randomness or disorder in a system or the increase of the ways to rearrange the components

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what is the entropy formula

S = k ln(W)
- k = 1.38x^-23
W = the number of ways to arrange the components

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what happens to S when W increases

S also increases

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what are some examples of a macrostate

P,V,T

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what is a microstate

number of different possible arrangements of molecular position and kinetic energy at a particular thermodynamic stat

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what is the relationship between entropy and microstates

entropy increases = # of microstates increases

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what is the second law of thermo

any spont process, the entropy of the universe increases (Suniv >0)
entropy is NOT conserved
systems proceed to increase the entropy of the univ

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what causes an increase in entropy

increase in temp
increase in moving molecules
increase in volume

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what does the change in entropy depend on

the initial and final states of the system S= Sfinal -Sinitial

how does temp increase cause an increase in entropy

increase in temp = increase in speed of moving particles = greater KE= microstates increase

will a increase in temp have a wider or skinner graph

wider graph

how does greater volume increase with entropy

greater volume = more number of positions for molecules to occupy

how does entropy increase with phase changes

more freedom of motion= increase in entropy Solids \< liquid

what is translational motion

whole atom or molecule changes its location in 3d space

what is rotational motion

whole molecule spins around an axis in 3D space

what is vibratinoal motion and what are the subtypes of vibrational motion

motion chat changes only the shape of the molecule 1, stretching, bending, internal rotation

when will entropy of a system also increase again

1. perform endothermic PHASE change 2. dissolve salt with lowly charged ions 3. # of moles increases during a chemical rxn

what has more motion an atomic or a molecule and what can't atoms do

a molecule atoms can't rotate

what is the equation for the System

qrev/T

what is the difference between reversible and irreversible

- irreversible cannot be undone - reversible can be undone

what processes are isothermal

melting and vaporization

what is qrev/T equivalent to

nHfus/ T

what are the SI units for Ssystem

J/K

what is the equation for Sunive

Syst + Surr = Suniv

what does Ssurr depend on

how much heat is absorbed or given

if Hsys is negative then what happens to the entropy of Surr

the entropy of the surroundings increases

what is the equation for Suniv when its a reversible process

Suniv = System + surrounds= 0

what is the equation for a irrevesible process for Suniv

Suniv = system + surr \> 0

sys (+) surr (+) Suniv (+) is it spontaneous or not

it is spontaneous

sys - surr = - univ = -

the reaction is not spontaneous in the forward but spontaneous in the reverse

sys = + surr = - univ =/

yes spontaneous if the system is larger than the surrounding

``` sys = - surr = + univ = ? ```

yes, if the surr is larger than the sys

what 2 factors are involved in spontaneous processes

1. decrease in energy of the system 2. @ a constant temp, increase in the amount of disorder

if H\>0 what will the spontaneity be

1. endothermic 2. spontaneous of S is \> 0 2 certain temps

if H\<0 what is the spontaneity

1. process is exothermic 2. if S \<0 then it is nonspon. at certain temps heat is exiting the system

what is Gibbs free energy and the equation

1. invented by american J gibbs 2. G = H-TS 3. free energy

What is the gibbs free energy equation for processes occurring at a constant temp

G = H-T (change in S)

what is the relationship between spontaneity with G and S

S \>0 and G\<0 then the reaction is spontaneous

if G \<0 then what direction

spontaneous in the forward direction; product favored

if G =0

at equilibrium

g\>0

reaction is nonspontaneous in the forward direction, aka react. favored

why is G preferred over Suniv

because G only depends on the system and avoids the complications of the surroundings

in the equation for free enerfy what represents the enthalpy and the entropy

delta H = enthalpy ( can be + or -) -Tdelta (s) = entropy ( s can be positive or negative)

if H\<0 and S\>0 what does it mean

rxn is spontaneous at all temps \* if S\<0 then the rxn is only spontaneous at low temps

if H\>0 and S\<0 then what does it mean

rxn is nonspontaneous at all temps \* if S\>0 the rxn is only nonspontaneous at low temps

what is the heat capacity

the amount of energy required to raise the temp of a substance by 1 K

what is the third law of thermodyamics

1. decrease the thermal energy = motional energy decreases 2. less energy is stored, entropy decreases 3. temp increased, atoms gain vibrational motion

what does the 3rd law of thermo say about the entropy of a pure crystalline

@ abs 0 is 0

what increases the standard molar entropies

1. generally increase w/ increasing molar mass 2. increase w/ the number of atoms

how to calculate Hrxn

nProducts - nReactants

what does the degree symbol mean on Gibbs free energy equation?

- standard conditions

when does Delta G = 0

elements that are in their standard states ex. H2, O2, n2

what rules do tou apply to delta G that are like hess's law

1. muliply by some factor, then Grxn is also multiplied by the same factor 2. flipped (change the sign of the Grxn)

how can a nonspontaneous reaction be made spontaneous

by coupling it with another process that is highly spontaneous

how does Delta G relate to Delta G (degrees)

1. as volume increases= microstates increases= decrease in pressure 2. for real reactions that are not under nonstandard conditions G = G + RT ln Q - R = 8.314J/mol.K Q= prod/react

what is G equation at equilibrium

K = e^-G/RT

how is work and free energy related to free energy

max work is equal to the change in free energy Wmax= G 1. nonspontaneous = minium amount of work 2. spontaneous = energy that is free to do useful work