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CHEM1603 Dina > Section C: thermodynamics > Flashcards

Section C: thermodynamics Flashcards

1
Q

what is the first law of thermodynamics?

A

energy is conserved ie. it cannot be created or destroyed

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2
Q

define ‘specific heat capacity’

A

the energy required to increase the temperature of 1g of water by 1C (= 1 calorie)

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3
Q

what is the relationship between calories and joules?

A

1 cal = 4.2 J

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4
Q

which combination of units is equal to 1 Coulomb?

A

1 C = 1 A.s

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5
Q

which combination of units is equal to 1 Volt?

A

1 V = 1 J.C^-1

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6
Q

what is the evidence for the first law of thermodynamics?

A

Joule’s Paddlewheel experiment showing the equivalence of work and heat

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7
Q

how is work done calculated?

A

E = Fx

where F = force; x = distance

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8
Q

define ‘specific latent heat’

A

the amount of energy in the form of heat required to effect a phase change in 1 kg of a substance without any change in temperature

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9
Q

how can the specific heat capacity be calculated from a graph of energy versus temperature?

A

it is equal to the gradient of the graph

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10
Q

what graph can be drawn to calculate the specific heat capacity?

A

energy versus temperature plot

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11
Q

what is the metabolic rate?

A

the rate of energy conversion ie. power dispersed

P = dE/dt

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12
Q

what is Kleiber’s Law?

A

P ∝ M^3/4

where P = metabolic rate; M = mass

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13
Q

what is the relationship between horsepower and Watts?

A

1 hp = 745.1 W

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14
Q

what is an open system?

A

exchange of energy and matter with the surroundings

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15
Q

what is a closed system?

A

exchange of energy but not of matter with the surroundings

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16
Q

what is an isolated system?

A

no exchange of energy or matter with the surroundings

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17
Q

what is an adiabatic system?

A

no exchange of heat with the surroundings

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18
Q

true or false: the Maxwell-Boltzmann distribution is symmetrical

A

false; it is asymmetrical and weighted towards lower speeds

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19
Q

what is the Boltzmann distribution function?

A

population En / population E0 = e^ -(En-E0) / kT

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20
Q

what is ‘k’?

A

Boltzmann’s constant

k = 1.38 x 10^-23 J.K^-1

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21
Q

what is the zeroth law of thermodynamics?

A 
energy flows in the form of heat between objects to equalise their temperature
if T(A) = T(B) and T(B) = T(C), then T(A) = T(C)
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22
Q

is temperature an intensive or extensive property?

A

intensive

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23
Q

define ‘intensive’ property

A

not additive; does not depend on the amount of material

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24
Q

define ‘internal energy’, U

A

the sum of all possible energies in the system

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25
Q

define ‘extensive’ property

A

additive; depends on the amount of material

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26
Q

since the absolute value of U cannot be determined, what calculation is performed instead?

A

ΔU = q + w

where q = heat transferred to the system; w = work done on the system

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27
Q

what is ‘q’?

A

heat transferred TO the system

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28
Q

what is ‘w’?

A

work done ON the system

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29
Q

what is a state function?

A

the value does not depend on the path taken to reach the specific value

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30
Q

what is the opposite of a state function?

A

a cell path function

31
Q

what are boundary phenomena?

A

energy is transferred across the system-surroundings boundary

32
Q

give two examples of boundary phenomena

A

q and w

33
Q

define ‘heat’

A

the transfer of energy due to a difference in temperature between the system and surroundings, resulting in a change in the random motion at the atomic level

34
Q

define ‘work’

A

the transfer of energy to/from the system that results in the coherent or coordinated motion of the molecules of a system

35
Q

how is work done minimised?

A

it is minimised if carried out reversibly ie. by infinitesimally small steps

36
Q

what does it mean if q > 0 ?

A

endothermic

energy transfer from surrounding to system

37
Q

what does it mean if q is less than 0?

A

exothermic

energy transfer from system to the surroundings

38
Q

what does it mean if w > 0 ?

A

the surroundings do work ON the system ie. the system gains energy

39
Q

what does it mean if w is less than 0?

A

the system does work ON the surroundings ie. the system loses energy

40
Q

how is work done minimised?

A

it is minimised if carried out reversibly ie. by infinitesimally small steps

41
Q

how else can work be written?

A

work = - pΔV = - Fx = - pAx

42
Q

how else can ΔU = q + w be written? what assumption does this rely on?

A

ΔU + pΔV = ΔH

at constant pressure, if volume does not change, q(p) = ΔH

43
Q

when volume and pressure are constant, what does the change in internal energy equal?

A

ΔU ≈ ΔH

44
Q

when volume and pressure are constant, what does the work done equal?

A

q(p) = ΔH

45
Q

define ‘enthalpy change’

A

the difference in energy used to break bonds in a chemical reaction and energy gained by the formation of new bonds

46
Q

what is meant if ΔH > 0 ?

A

the reaction is endothermic

47
Q

what is meant if ΔH is less than 0?

A

the reaction is exothermic

48
Q

describe the nature of enthalpy

A
  • state function
  • extensive and additive
  • the absolute value cannot be measured, only differences
  • changes in pressure, temperature, etc. result in changes in H
49
Q

what information is provided by entropy?

A

the direction of spontaneous change

50
Q

what are the units of entropy?

A

kJ.mol^-1.K^-1

51
Q

what is the relationship between entropy, heat/energy change and temperature?

A

ΔS ≥ q/T

where q = heat/energy change; T = temperature

52
Q

how is entropy minimised?

A

it is minimised if carried out reversibly ie. by infinitesimally small steps

53
Q

what is the relationship between ΔS(cold) and ΔS(hot)?

A

|ΔS(cold)| > |ΔS(hot)|

since ΔS(cold) > 0; ΔS(hot) is less than 0

54
Q

what is the relationship between ΔS(cold) and ΔS(hot) when the reaction is reversible?

A

ΔS(cold) + ΔS(hot) = 0

55
Q

which of ΔS(hot) and ΔS(cold) is less than zero, and which is greater?

A

ΔS(cold) > 0

ΔS(hot) is less than 0

56
Q

what is the second law of thermodynamics?

A
  • the entropy of the universe will increase over time
  • in any spontaneous process, the entropy will increase
  • the entropy of the universe is never negative
57
Q

what is the third law of thermodynamics?

A
  • for any perfect crystal, at T = 0, the entropy is zero

- entropy increases with degrees of freedom and molecular size

58
Q

what is the Boltzmann equation?

A

S = klnW

59
Q

what is the mole fraction?

A

moles of A / total moles of everything

60
Q

what is molality?

A

moles of solute / mass of solvent

units mol.kg^-1

61
Q

what is the relationship between molality and the mole fraction?

A

molality ∝ mole fraction

62
Q

what is meant by biological systems being isothermal?

A

they do not rely on changes in temperature to do work

63
Q

how is the Gibbs free energy calculated?

A

ΔG = ΔH - TΔS

requiring fixed pressure and temperature

64
Q

what are the requirements for measuring ΔG?

A

fixed pressure and temperature

65
Q

what is meant by μ?

A

chemical potential = the measure of how Gibbs energy changes per molecule of substance

66
Q

when is the chemical potential highest?

A

for a pure liquid

67
Q

what is indicated by differences in μ?

A

in which direction molecules move

68
Q

what is the chemical potential for a gas, A?

A

μ(A) = μ0(A) + RTlnP

where P = pressure

69
Q

what is the chemical potential for a liquid, A?

A 
μ(A) = μ0(A) + RTlnx(A)
where x(A) is the mole fraction
70
Q

what is the relationship between ΔG and the equilibrium constant, k?

A

ΔG = - RTlnk

71
Q

what is osmotic pressure proportional to?

A

osmotic pressure (π) ∝ molarity

72
Q

how is the osmotic pressure calculated?

A

π = iMRT
where i is the dimensionless van’t Hoff factor; M = molarity; R is the gas constant = 0.082 L.atm.K^-1.mol^-1; T = temperature

73
Q

what are the units of osmotic pressure?

A

atm

74
Q

what is the van’t Hoff formula?

A

π = iMRT

CHEM1603 Dina (9 decks)

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