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Chem 1220 > Chpt 19: Chemical Thermodynamics > Flashcards

Chpt 19: Chemical Thermodynamics Flashcards

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1
Q

True or false: molar entropy at 298 Kelvin increases as you go down the periodic table????

A

True (but I don’t understand why)

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2
Q

what are the 3 scenarios in which entropy is expected to increase?

A
  1. when solids or liquids go to gas
  2. when solids go into solution
  3. when the number of gas molecules increases
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3
Q

True or false: because all spontaneous processes are REAL processes, spontaneous processes are irreversible?

A

True

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4
Q

does the delta entropy equation get applied to non-isothermal conditions?

A

no. The entropy equation works BECUSE it’s applied to isothermal conditions

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5
Q

True or false: entropy is a reflection of the net energy change associated with spontaneous processes

A

true

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6
Q

what is happening to a molecule when it is engaged in ROTATIONAL motion?

A

the entire molecule is tumbling about itself

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7
Q

what is happening to a molecule when it is engaged in vibrational motion?

A

it’s atoms are moving around relative to one another

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8
Q

true or false: more molar mass (of a substance) means large molar entropy?

A

yes; more atoms means larger standard molar entropy

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9
Q

what is absolute entropy?

A

the change in entropy that occurs when you raise the temp of a material from 0 kelvin (aka absolute 0) to some other temperature

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10
Q

under what circumstances will entropy of surroundings and entropy of system have equal but opposite values?

A

in IRreversible processes (non spontaneous processes)

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11
Q

what does the 2nd law of thermodynamics state?

A

spontaneous process ALWAY result in increased entroyp in the universe

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12
Q

do reversible processes ever result in increased universe entropy?

A

generally, no

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13
Q

why is the equation for entropy based on the heat of the reverse of a process?

A

because this specifies a single path being taken (rather than forcing you to account for all the possible paths that could be taken) to get from initial to final

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14
Q

what are the units for delta entropy?

A

J/K

Joules/Kelvin

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15
Q

what are ‘standard state’ conditions for substances examined in entropy problems?

A

1atm
298 K

for one mole of pure substance

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16
Q

which 2 thermodynamic quantities are NOT state functions?

A

q and w

their values depend on paths taken

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17
Q

if the flow of heat into or out of a system is reversible, what must be true about the rate of heat transfer?

A

the rate of heat flow must be infinitesimally slow

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18
Q

what is a ‘state’ (aka ‘thermodynamic state’) of a system composed of?

A

all of the microstates of its particles.

It’s a huge number

19
Q

true or false: the more kinds of motion a molecule can do, the more microstates it can have?

A

true

20
Q

true or false: the more complex a molecule is, the more kinds of motion it can do

A

true

21
Q

how does Boltzman describe entropy mathematically?

A

entropy = the number of microstates associated with a given macrotrostate

22
Q

what is the free energy for pure elements in their standard state?

A

0

23
Q

what is thermodynamics the study of?

A

energy and its transformation

24
Q

why are we even bothering to learn about reversible processes?

A

I don’t know. It’s not like changes aren’t being made to the system. Changes ARE being made to the system. They’re just really small. This shouldn’t count as a thing.

25
Q

what does the third law of thermodynamic state?

A

pure crystalline solid has 0 entropy at zero Kelvin

26
Q

do irreversible processes always result in increased universe entropy?

A

generally, yes

27
Q

what is a ‘state’ also known as?

A

macrostate

thermodynamic state

28
Q

are phase changes isothermal?

A

yes

temp does not change while phase is changing; all energy is being used to facilitate the phase change; none is being use to change the temperature

29
Q

does making a solution increase entropy or decrease entropy?

A

it decreases entropy for the water (bc hydration) but increases entropy much more for the solute (bc dissolution).

Overall, making a solution increases entropy.

30
Q

what is standard molar entropy?

A

the entropy content of one mole of substance under a standard state (298 K)

compare this to the molar entropy of zero when the substance at zero Kelvin

31
Q

what is a reversible process?

A

one in which the system can be restored to its original state without changing the surroundings

one that reverses direction whenever an infinitesimal change is made in some property of the system

32
Q

what does it mean to say that a process is isothermal?

A

it means that the process occurs at constant temperature

33
Q

what does the term ‘microstate’ represent

A

each of the possible kinetic energies (velocities) and positions in space that a given molecule in a system can have

34
Q

are phase changes good indicators of changes in entropy?

A

yes

35
Q

if the flow of heat into or out of a system is reversible, what must be the about the change in temperature?

A

the change in temperature must be infinitesimally small

36
Q

what is absolute temperature?

A

temperature as measured in Kelvin

37
Q

is entropy a state function?

A

yes

it exits independent of path taken

38
Q

True or false: ‘spread out’ energy (entropy) is less able to do work

A

true

39
Q

what are the two main traits of an IRreversible process?

A
  1. the surroundings involved have to be changed in order to restore a system to its original state.
  2. the path taken by the reverse process is different than the path taken by the forward process
40
Q

why does entropy in a gas increase when/if you add more particles?

A

because more particles = more microstates = increased entropy

41
Q

what kind of motion can molecules do (even though atoms can’t)?

A

vibrational movement and rotational movement.

Atoms can only do translational movement

42
Q

why is the equation for delta entropy based on the heat of the reverse of a process?

A

because this specifies a single path being taken (rather than forcing you to account for all the possible paths that could be taken) to get from initial to final

43
Q

True or false: learning about reversible processes is stupid because all REAL processes are IRreversible

A

true. all Real processes are effectively irreversible

44
Q

True or false: as energy becomes more ‘spread out’ as it’s transformed and/or used to do work, an increase in entropy results

A

true

Chem 1220 (9 decks)

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