Ch. 7: Thermochemistry Flashcards

1
Q

Can an Isolated System exchange energy or matter with the surroundings

A

no exchange of energy (heat or work) with surroundings

ex: insulated bomb calorimeter

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2
Q

Can a Closed System exchange energy or matter with the surroundings

A

exchange of energy (heat or work) but not matter with surroundings

ex: steam radiator

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3
Q

Can an Open System exchange energy or matter with the surroundings

A

exchange of energy (heat or work) and matter with surroundings

ex: pot of boiling water

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4
Q

what is a process

A

changing in one of the properties of a system

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5
Q

equation for delta U

A

delta U = Q - W

change in internal energy of a system = heat added - work done by system

FIRST LAW OF THERMO

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6
Q

what occurs in an isothermal process

A
  • temperature is constant
  • U (total internal energy) is constant, delta U = 0
  • Q = W
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7
Q

what occurs in an adiabatic process

A
  • no heat is exchanged between system and environment (temperature can change)
  • Q = 0
  • delta U = - W (change in internal energy = work done on the system)
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8
Q

what occurs in an isobaric process

A
  • pressure is constant

- delta U = Q - W

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9
Q

what occurs in an isovolumetric (isochoric) process

A
  • volume is constant
  • no change in volume = W = 0
  • delta U = Q
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10
Q

how is a spontaneous process driven

A

occurs internally WITHOUT drive by outside energy source

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11
Q

what is accomplished by coupling

A

energy for nonspontaneous rxns is supplied by linking them with spontaneous rxns

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12
Q

state functions

A

properties of a system at equilibrium

  • pressure (P)
  • density (p)
  • temperature (T)
  • volume (V)
  • enthalpy (H)
  • internal energy (U)
  • Gibbs free energy (G)
  • entropy (S)
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13
Q

process functions

A

properties of a system in flux

  • work (W)
  • heat (Q)
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14
Q

standard condition

A
  • 25 degrees C (298K)
  • 1 atm
  • 1 M con’c

used for kinetics, e’q, and thermo, measuring H, G, S

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15
Q

standard temperature and pressure

A
  • 0 degrees C (273K)
  • 1 atm

used for ideal gas calculations

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16
Q

what is the standard state of a substance

A

the most stable state of the substance under standard conditions

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17
Q

evaporation/vaporization

A

liquid to gas phase change

molecules near the surface of liquid have enough kinetic energy to escape into the gas phase

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18
Q

condensation

A

gas to liquid phase change

molecules are forced by a lower temperature or higher pressure back into the liquid phase

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19
Q

fusion/melting

A

solid to liquid phase change

molecules in the solid absorb enough energy to break into liquid phase

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20
Q

solidification/crystallization/freezing

A

liquid to solid phase change

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21
Q

sublimation

A

solid to gas phase change

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22
Q

deposition

A

gas to solid phase change

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23
Q

triple point

A

point at which three boundaries meet on a phase diagram

24
Q

critical point

A

point at which the phase boundary for liquid and gas terminate
(no distinction between the phases at this point)

25
Q

what does temperature measure

A

average kinetic energy of particles of a substance

26
Q

what does heat measure

A

transfer of energy from one substance to another as a result of difference in temperature

27
Q

endothermic process delta Q

A

delta Q > 0

system absorbs heat

28
Q

exothermic process delta Q

A

delta Q < 0

system releases heat

29
Q

calorimetry

A

the process of measuring transferred heat

30
Q

equation for heat absorbed/released in a process

A

q = mcdelta T

heat = mass * specific heat * change in temperature

31
Q

specific heat (c)

A

amount of energy required to raise the temperature of one gram of substance by one degree C or K

32
Q

equation for heat capacity

A

m*c

33
Q

equation for heat absorbed/released during a phase change

A

q = m*L

heat = mass * latent heat

34
Q

latent heat

A

enthalpy of an isothermal process

35
Q

what does changes in enthalpy represent for a reaction

A

changes in heat at constant pressure

36
Q

equation for delta H of a reaction

A

delta H rxn = H products - H reactants

37
Q

endothermic process delta H

A

positive

products have more heat than reactants
heat is absorbed in reaction

38
Q

exothermic process delta H

A

negative

products have less heat than reactants
heat is expressed in reaction

39
Q

standard element of formation

A

enthalpy required to produce one mole of a compound from its elements in their standard states

40
Q

standard enthalpy of a reaction

A

enthalpy change accompanying a rxn being carried out under standard conditions.

delta H rxn at standard conditions

41
Q

Hess’s Law

A

state function changes of a reaction are additive

ENTHALPY, ENERGY, GIBBS FREE ENERGY

42
Q

bond dissociation energy

A

average energy that is required to break a particular bond type

43
Q

standard heat of combustion

A

enthalpy change associated with the combustion of a fuel

44
Q

what does changes in entropy measure

A

spontaneous dispersal of energy at specific temperature

45
Q

equation for entropy

A

delta S = Qrev / T

change in entropy = heat gained/lost in reversible process / T in kelvin

46
Q

units of entropy

A

J / mol * K

47
Q

units of enthalpy

A

J * mol

48
Q

what does Gibbs free energy measure

A

maximum amount of energy released by a process occurring at a constant temp and pressure that is available to perform work

49
Q

equation for Gibbs free energy

A

delta G = delta H - [T*delta S]

free energy = enthalpy - temp * entropy
goldfish are horrible without tartar sauce

50
Q

exergonic reactions

A
  • move toward eq’ position
  • decrease in free energy
  • releases energy
  • spontaneous
51
Q

endergonic reactions

A
  • move away from eq’ position
  • increase in free energy
  • absorb energy
  • non spontaneous
52
Q

negative delta G

A

spontaneous

53
Q

positive delta G

A

nonspontaneous

54
Q

zero delta G

A

equilibrium

delta H = T*delta S

55
Q

when is delta G temperature dependent

A

when delta S and delta H have the same sign