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chemistry 1302 gen chem 2 > chapter 16: spontaneous entropy > Flashcards

chapter 16: spontaneous entropy Flashcards

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1
Q

what is the first law of thermodynamics

A
  1. energy cannot be created or destroyed
  2. total energy of the Universe is constant
    - 3. energy can be transferred
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2
Q

what is the equation for
Euniverse

A

Euniverse= 0= Esystem + Esurroundings

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3
Q

what is internal energy

A

the total energy in a system ( kinetic + potential)

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4
Q

what is a spontaneous process?

A

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

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5
Q

what is a nonspontaneous process

A
  • requires energy to proceed
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6
Q

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

A

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

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7
Q

what is an example of of a spontaneous process

A

nail rusting

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8
Q

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

A
  1. above 0 degrees is spontaneous to melt
  2. below 0 is spont. for ice to form
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9
Q

does rate or speed affect spontaneity

A

no, a process can be spontaneous and slow

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10
Q

what is the difference between thermodynamics and kinetics

A
  1. thermodynamics tells us the DIRECTION and EXTENT of the rxn
  2. Kinetics tells us the speed of the reaction
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11
Q

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

A

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

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12
Q

if a decompose H2O into H2 and O2

A

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

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13
Q

endothermic does not equal

A

nonspontaneous

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14
Q

most spontaneous processes are what

A

exothermic but some are endothermic

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15
Q

what are the two factors that are involved in spontaneous processes

A
  1. decrease in the energy (enthalpy)
  2. @ a constant temp, an increase in the disorder of a system ( entropy)
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16
Q

what is the symbol for entropy

A

S

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17
Q

what is entropy

A

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

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18
Q

what is the entropy formula

A

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

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19
Q

what happens to S when W increases

A

S also increases

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20
Q

what are some examples of a macrostate

A

P,V,T

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21
Q

what is a microstate

A

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

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22
Q

what is the relationship between entropy and microstates

A

entropy increases = # of microstates increases

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23
Q

what is the second law of thermo

A
  1. any spont process, the entropy of the universe increases (Suniv >0)
  2. entropy is NOT conserved
  3. systems proceed to increase the entropy of the univ
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24
Q

what causes an increase in entropy

A
  1. increase in temp
  2. increase in moving molecules
  3. increase in volume
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25
Q

what does the change in entropy depend on

A

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

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26
Q

how does temp increase cause an increase in entropy

A

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

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27
Q

will a increase in temp have a wider or skinner graph

A

wider graph

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28
Q

how does greater volume increase with entropy

A

greater volume = more number of positions for molecules to occupy

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29
Q

how does entropy increase with phase changes

A

more freedom of motion= increase in entropy
Solids < liquid

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30
Q

what is translational motion

A

whole atom or molecule changes its location in 3d space

31
Q

what is rotational motion

A

whole molecule spins around an axis in 3D space

32
Q

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

A

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

33
Q

when will entropy of a system also increase again

A
  1. perform endothermic PHASE change
  2. dissolve salt with lowly charged ions
  3. # of moles increases during a chemical rxn
34
Q

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

A

a molecule
atoms can’t rotate

35
Q

what is the equation for the System

A

qrev/T

36
Q

what is the difference between reversible and irreversible

A
  • irreversible cannot be undone
  • reversible can be undone
37
Q

what processes are isothermal

A

melting and vaporization

38
Q

what is qrev/T equivalent to

A

nHfus/ T

39
Q

what are the SI units for Ssystem

A

J/K

40
Q

what is the equation for Sunive

A

Syst + Surr = Suniv

41
Q

what does Ssurr depend on

A

how much heat is absorbed or given

42
Q

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

A

the entropy of the surroundings increases

43
Q

what is the equation for Suniv when its a reversible process

A

Suniv = System + surrounds= 0

44
Q

what is the equation for a irrevesible process for Suniv

A

Suniv = system + surr > 0

45
Q

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

A

it is spontaneous

46
Q

sys -
surr = -
univ = -

A

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

47
Q

sys = +
surr = -
univ =/

A

yes spontaneous if the system is larger than the surrounding

48
Q 
sys = - 
surr = + 
univ = ?
A

yes, if the surr is larger than the sys

49
Q

what 2 factors are involved in spontaneous processes

A
  1. decrease in energy of the system
  2. @ a constant temp, increase in the amount of disorder
50
Q

if H>0 what will the spontaneity be

A
  1. endothermic
  2. spontaneous of S is > 0 2 certain temps
51
Q

if H<0 what is the spontaneity

A
  1. process is exothermic
  2. if S <0 then it is nonspon. at certain temps

heat is exiting the system

52
Q

what is Gibbs free energy and the equation

A
  1. invented by american J gibbs
  2. G = H-TS
  3. free energy
53
Q

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

A

G = H-T (change in S)

54
Q

what is the relationship between spontaneity with G and S

A

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

55
Q

if G <0 then what direction

A

spontaneous in the forward direction; product favored

56
Q

if G =0

A

at equilibrium

57
Q

g>0

A

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

58
Q

why is G preferred over Suniv

A

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

59
Q

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

A

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

60
Q

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

A

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

61
Q

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

A

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

62
Q

what is the heat capacity

A

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

63
Q

what is the third law of thermodyamics

A
  1. decrease the thermal energy = motional energy decreases
  2. less energy is stored, entropy decreases
  3. temp increased, atoms gain vibrational motion
64
Q

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

A

@ abs 0 is 0

65
Q

what increases the standard molar entropies

A
  1. generally increase w/ increasing molar mass
  2. increase w/ the number of atoms
66
Q

how to calculate Hrxn

A

nProducts - nReactants

67
Q

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

A
  • standard conditions
68
Q

when does Delta G = 0

A

elements that are in their standard states

ex. H2, O2, n2

69
Q

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

A
  1. muliply by some factor, then Grxn is also multiplied by the same factor
  2. flipped (change the sign of the Grxn)
70
Q

how can a nonspontaneous reaction be made spontaneous

A

by coupling it with another process that is highly spontaneous

71
Q

how does Delta G relate to Delta G (degrees)

A
  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

72
Q

what is G equation at equilibrium

A

K = e^-G/RT

73
Q

how is work and free energy related to free energy

A

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
74
Q
A

chemistry 1302 gen chem 2 (10 decks)

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