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Medicinal Chemistry > Thermodynamics > Flashcards

Thermodynamics Flashcards

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1
Q

What is thermodynamics?

A

The science of the relationship between heat + other forms of energy

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2
Q

What is thermochemistry?

A

The study of quantity of heat absorbed or evolved by chemical reactions

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3
Q

What is energy?

A

The capacity to do work

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4
Q

What are the different types of energy?

A 
Radiant energy
Thermal energy
Chemical energy
Nuclear energy
Potential energy
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5
Q

What is kinetic energy?

A

The energy of motion

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6
Q

What is potential energy?

A

Stored energy

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7
Q

What is thermal energy?

A

Kinetic energy of molecular motion, measured by finding the temperature of an object

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8
Q

What is heat?

A

The amount of thermal energy transferred from one object to another as a result of temperature difference between the two

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9
Q

What is the law of conservation of energy?

A

Energy cannot be created or destroyed

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10
Q

What is the 1st law of thermodynamics?

A

Energy cannot be created or destroyed

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11
Q

What can isolated systems not do?

A

Neither do work upon nor heat their surroundings

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12
Q

Because isolated systems cannot do work or heat their surroundings what does it mean?

A

Internal energy of isolated systems remain constant

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13
Q

How do you calculate energy?

A

ΔE =E final - E initial

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14
Q

What is an exothermic process?

A

A release of heat corresponding to a decrease in enthalpy

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15
Q

What is an endothermic process?

A

An input of heat that corresponds to an increase in enthalpy

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16
Q

What is an open system?

A

Can exchange both matter + energy with the surroundings

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17
Q

What is a closed system?

A

Can exchange only energy with surroundings

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18
Q

What is an isolated system?

A

Can exchange neither energy nor matter with its surroundings

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19
Q

What is a state function?

A

Use to quantify the heat foe into or out of a system under constant pressure

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20
Q

How do you calculate work?

A

Force X Distance

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21
Q

What is expansion work?

A

Work done as a result of a volume change in the system

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22
Q

What is enthalpy?

A

A state function whose value depends on the current state of the system, not the path taken to arrive at that state

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23
Q

What is the equation if the vol is constant?

A

qv = ΔE

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24
Q

What is the equation if pressure is constant?

A

qp = ΔE + PΔV

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25
Q

What is the equation for enthalpy change?

A

ΔH = products - reactants

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26
Q

What is thermodynamic standard state?

A

Most stable form of a substance at 1 atm pressure + at 25 degrees at 1M conc

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27
Q

What is the equation for work?

A

Work = -PΔV

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28
Q

How do you calculate work?

A

Calculate vol = final - initial
Calculate pressure = X atm
Put into equation
Then cancel out units to give J

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29
Q

What is enthalpy of fusion?

A

The amount of heat necessary to melt a substance without changing its temp

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30
Q

What is enthalpy of vaporisation?

A

The amount of heat required to vaporise a substance without changing its temp

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31
Q

What is enthalpy of sublimation?

A

The amount of heat required to convert a substance from a solid to a gas without going through a liquid phase

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32
Q

What is H2O (s) —-> H2O (l)?

A

Endothermic

= +ΔH

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33
Q

What is H2O (l) —-> H2O (s)?

A

Exothermic

= -ΔH

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34
Q

How do you calculate ΔE?

A

ΔE = ΔH - PΔV

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35
Q

What is calorimetry?

A

Measure of heat flow at constant pressure

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36
Q

What is differential scanning calorimetry?

A

Measures difference in heat transferred to + from sample in comparison to reference material

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37
Q

What is heat capacity?

A

The amount of heat required to raise the temp of an object by a given amount

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38
Q

What is the equation for heat capacity?

A

q = C X ΔT

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39
Q

What is molar heat capacity?

A

The amount of heat required to raise the temperature of 1 mol of a substance by 1 degree

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40
Q

What is the equation for molar heat capacity?

A

q = Cm X moles of substance X ΔT

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41
Q

What is specific heat?

A

The amount of heat required to raise the temp of 1g of a substance by 1 degree?

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42
Q

What is the equation for specific heat?

A

q = specific heat X mass of substance X ΔT

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43
Q

What is Hess’s Law?

A

The overall enthalpy change for a reaction is equal to the sum of the enthalpy changes for individual steps in the reaction

44
Q

What is the equation for the Haber process?

A

3H2 (g) + N2 (g) —-> 2NH3 (g)

45
Q

What is the standard enthalpy of formation?

A

Heat change when 1 mole of a compound is formed from its elements at a pressure of 1 atm

46
Q

How do you calculate ΔH for standard enthalpy of formation?

A

Products - reactants

47
Q

What is standard heat of formation?

A

Enthalpy change of formation of 1 mol of a substance in its standard state from its constituent elements in their standard state

48
Q

What are the steps for calculating standard enthalpy of formation?

A

Write enthalpy of formation reaction

Add given rxns so that it gives desired rxn

49
Q

What is bond breaking?

A

Endothermic

50
Q

What is bond making?

A

Exothermic

51
Q

What is bond dissociation energy?

A

Amount of energy that must be supplied to break chemical bond in an isolated molecule in gaseous state + so amount of energy released when bond forms

52
Q

What do exact values depend on?

A

Bond order + electronic environment of 2 atoms compromising the bond

53
Q

How do you calculate bond enthalpies?

A

Reactants - products

54
Q

What does it mean if the more oxidised a fuel is?

A

Less energy we can get from its combustion

55
Q

What is a spontaneous process?

A

A process that, once started, proceeds on its own without a continuous external influence

56
Q

When will a spontaneous reaction occur slowly?

A

If it has a high Ea

57
Q

What is entropy?

A

The amount of molecular randomness in a system

58
Q

When are spontaneous processes favoured?

A

Decrease in H (-ΔH)

Increase in S (+ΔS)

59
Q

What is the equation for ΔS?

A

S final - S initial

60
Q

What happens to entropy as order increases?

A

Decreases

61
Q

What happens to entropy as disorder increases?

A

Increases

62
Q

Describe entropy of solid, liquid + gas

A

Solid < liquid < gas

63
Q

What is entropy?

A

Is the measure of how dispersed energy + matter is

64
Q

What is change in entropy equal to?

A

The heat transferred reversibly to it, divided by the temp at which the transfer takes place

65
Q

Is entropy a state function?

A

YES

66
Q

What is the 2nd Law of Thermodynamics got to do with?

A

Entropy

67
Q

Why is entropy reversible?

A

Equal temp at either side of thermally conducting walls

68
Q

Why is entropy heat?

A

Because its random molecular motion

Work = ordered molecular motion

69
Q

Why does entropy got to do with temperature?

A

Accounts for randomness of molecular motion

70
Q

When is a given entropy change most significant?

A

For cold system

71
Q

How do you calculate entropy of heating H2O?

A

ΔS = q rev/T

72
Q

How do you calculate ΔS accompanying heating?

A

ΔS =C In (Tf/Ti)
C = heat capacity of system
Ti = initial temp
Tf = final temp

73
Q

What does it mean when Tf > Ti?

A

Log is positive = ΔS > 0 = what we would expect

74
Q

When are entropy changes higher?

A

Things with high heat capacities

75
Q

What are phase transitions accompanied by?

A

Entropy changes

76
Q

Why does entropy increase in phase transitions?

A

Molecules are able to move more freely upon melting or boiling = increase entropy

77
Q

How do you calculate entropy of vaporisation of H2O?

A

ΔS1 = C p,m(H2O, L)In(Tf/Ti)
ΔS2 = ΔvapH(Tb)/Tb
ΔS3 = C p,m(H2O, g)In(Tf/Ti)
ΔS1 + ΔS2 + ΔS3

78
Q

What is C p,m?

A

Molar heat capacity at constant pressure

79
Q

What is 2nd Law of Thermodynamics?

A

The amount of heat passing to/from the surroundings is equal + opposite to the heat leaving/entering the system

80
Q

How do you calculate entropy of surroundings?

A

ΔS sur = -ΔH/T

81
Q

What is the main 2nd Law of Thermodynamics?

A

The entropy of the universe increases in spontaneous process + remains unchanged in an eqm process

82
Q

What is the 3rd Law of Thermodynamics?

A

The entropy of a perfectly ordered crystalline substance at 0K is zero

83
Q

What happens at a higher temp?

A

Greater molecular motion
Broader distribution of individual molecular energies
More randomness
Higher entropy

84
Q

What happens at lower temp?

A

Less molecular motion
Narrower distribution of individual molecular energies
Less randomness
Lower entropy

85
Q

What are absolute entropies equal to?

A

Absolute zero

86
Q

What is standard molar entropy?

A

The entropy of 1 mole of a pure substance at 1 atm pressure + specified temp

87
Q

What is the standard entropy of reaction?

A

The entropy change for a reaction carried at 1 atm + 25 degrees

88
Q

When do processes occur spontaneously?

A

If overall entropy of universe increases

89
Q

How do you calculate entropy of universe?

A

ΔS sys - ΔH/T

At constant temp + pressure

90
Q

What is Gibbs Free Energy equation?

A

ΔG = ΔH - TΔS

91
Q

What is the reaction at constant temp when ΔG < 0?

A

Spontaneous in forward direction

92
Q

What is the reaction at constant temp when ΔG > 0?

A

Spontaneous in backwards direction

93
Q

What is the reaction at constant temp when ΔG = 0?

A

Reaction at eqm

94
Q

What is the ΔG of any process?

A

The max non-expansion work that can be extracted from process at constant temp + pressure

95
Q

How do you calculate standard free energies of formation?

A

ΔG = products - reactants

96
Q

How do you calculate ΔG under non-standard conditions?

A

ΔG = ΔG° + RT In K

97
Q

How do you calculate ΔrG°?

A

-RT In K

98
Q

What happens when a reaction mixture is mostly reactants?

A

K < 1
RT In K < 0
ΔG < 0
Total free energy decreases as reaction proceeds spontaneously in forwards direction

99
Q

What happens when a reaction mixture is mostly products?

A

K > 1
RT In K > 0
ΔG > 0
Total free energy decreases as reaction proceeds spontaneously in backwards direction

100
Q

What is Ki?

A

Inhibitor constant

101
Q

What is ionic bond value?

A

20-40 kJ/mol

102
Q

What is polarisation effects important for?

A

Soft atoms

eg. sulphur

103
Q

What are dispersion effects important for?

A

Attractive component of van der Waals interactions

104
Q

What is H bonding important for?

A

Angular dependence which produces directionality in binding

105
Q

What is H bonding drug binding?

A

Thermoneutral

106
Q

What do organic molecules want to do in aq environment?

A

Come together

= hydrophobic effect = form droplets

107
Q

What is effective drug design?

A

Compromise between enthalpic + entropic considerations

Medicinal Chemistry (19 decks)

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