Chapter 19: Thermochemistry Flashcards

1
Q

second law of thermodynamics:

A

the pervasive tendency for energy to spread out or dissipate when not prevented from doing so

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2
Q

the second law determines…

A

spontaneous direction of all processes

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3
Q

spontaneous process occurs..

A

without outside intervention

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4
Q

what is the spontaneity of a reaction?

A

the direction in which, and the extent to which, a chemical reaction proceeds

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5
Q

a rxn may be thermodynamically spontaneous but kinetically BLANK at a give temp

A

slow

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6
Q

what effect does a catalyst have on a chemical rxn

A

the rate of a spontaneous process can be increased by a catalyst, but a nonspontaneous process can’t be made spontaneous by te use of a catalyst

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7
Q

thermodynamics deals with the relative chemical potentials of the BLANK and BLANK

A

reactants and products

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8
Q

how can a nonspontaneous process be made spontaneous?

A

by coupling the nonspontaneous rxn to another process that is spontaneous or by supplying energy from an external source

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9
Q

most spontaneous processes are what kind of rxns

A

exothermic

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10
Q

what type of process do you have when a highly ordered arrangement goes to a disorderly arrangement

A

spontaneous

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11
Q

entropy:

A

quantity related to disorder or randomness at the molecular level

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12
Q

sign for entropy

A

S

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13
Q

what are the units of entropy

A

J/K

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14
Q

if conditions P,V, and T remain constant, the energy of the system..

A

also remains constant

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15
Q

microstate:

A

exact internal energy distribution among the particles at any one instant

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16
Q

microstate in simpler terms:

A

snapshot of the system at a given instant in time

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17
Q

macrostate:

A

composed of several microstates, each with a different number of molecules and/or different arrangement of molecules

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18
Q

greater entropy says what about arrangment?

A

greater entropy means more energetically equivalent ways to arrange the components of a system

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19
Q

if state A is highly dispersed and state B is highly concentrated, which has the higher entropy?

A

state A

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20
Q

processes that decrease the entropy of the university occur spontaneously or nonspontaneously

A

nonspontaneously

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21
Q

entropy is what kind of function?

A

state function

22
Q

formula for change in entropy:

A

change in S = Sfinal - Sinitial

23
Q

chemical system proceeds in a direction that BLANK the entropy of the universe

24
Q

A gas has more BLANK than a solid

A

microstates

25
a change in state is accompanied by an exchange of
heat between the system and surroundings
26
equation for change in entropy at constant temperature
change in S = (qreverse)/T
27
All reversible processes are in a constant...
state of equilibrium
28
formula for entropy of universe:
change S universe = (change in S system) + (change S surroundings)
29
an exothermic process BLANK entropy of surroundings
increases
30
an endothermic process BLANK entropy of surroundings
decreases
31
The greater the temperature, the smaller the BLANK in entropy for a given amount of energy dispersed into the surroundings
increase
32
the higher the temperature the BLANK the impact
smaller
33
at low temperatures, the decrease in entropy of the system is BLANK by the large increase in the entropy of the surroundings
overcome
34
the change in entropy of the surroundings depends on what two things?
(a) the amount of heat transferred into or out of the surroundings (b) the temperature of the surroundings
35
first law of thermodynamics:
any heat leaving the system must go into the surroundings and vice versa
36
A process that emits heat into the surroundings does what to the surroundings?
increases the entropy of the surroundings
37
A process that absorbs heat from the surroundings does what to the surroundings?
decreases the entropy of the surroundings
38
exothermic processes have a tendency to be spontaneous at what temperatures
low temperatures
39
formula for free energy:
change in G = enthalphy - T*entropy
40
a negative value of G corresponds to :
spontaneous process
41
what values of for enthalpy and entropy produce a process that is spontaneous at all temperatures?
negative H, positive S... because entropy of both system and surroundings increases
42
what values of for enthalpy and entropy produce a process that is not spontaneous at all temperatures?
postive H, negative S
43
negative H and negative S yields a spontaneous process at what temperatures
low temperatures
44
formula for standard entropy of rxn
Srxn = Sproducts - S reactants
45
third law of thermodynamics:
the entropy of a perfect crystal at absolute zero (0K) is zero
46
allotropes
elements that exist in two or more forms within the same state
47
as molar mass increases, what happens to standard entropies?
increase
48
allotropes that allow for more freedom of molecules have what kind of standard entropies?
greater entropies
49
how does increasing molecular complexity affect entropy
entropy increases
50
The dissolution of a crystalline solid into solution usually results in an BLANK in entropy
increase
51