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Thermodynamics Flashcards

(107 cards)

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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
What is the equation for enthalpy change?
ΔH = products - reactants
26
What is thermodynamic standard state?
Most stable form of a substance at 1 atm pressure + at 25 degrees at 1M conc
27
What is the equation for work?
Work = -PΔV
28
How do you calculate work?
Calculate vol = final - initial Calculate pressure = X atm Put into equation Then cancel out units to give J
29
What is enthalpy of fusion?
The amount of heat necessary to melt a substance without changing its temp
30
What is enthalpy of vaporisation?
The amount of heat required to vaporise a substance without changing its temp
31
What is enthalpy of sublimation?
The amount of heat required to convert a substance from a solid to a gas without going through a liquid phase
32
What is H2O (s) ----> H2O (l)?
Endothermic | = +ΔH
33
What is H2O (l) ----> H2O (s)?
Exothermic | = -ΔH
34
How do you calculate ΔE?
ΔE = ΔH - PΔV
35
What is calorimetry?
Measure of heat flow at constant pressure
36
What is differential scanning calorimetry?
Measures difference in heat transferred to + from sample in comparison to reference material
37
What is heat capacity?
The amount of heat required to raise the temp of an object by a given amount
38
What is the equation for heat capacity?
q = C X ΔT
39
What is molar heat capacity?
The amount of heat required to raise the temperature of 1 mol of a substance by 1 degree
40
What is the equation for molar heat capacity?
q = Cm X moles of substance X ΔT
41
What is specific heat?
The amount of heat required to raise the temp of 1g of a substance by 1 degree?
42
What is the equation for specific heat?
q = specific heat X mass of substance X ΔT
43
What is Hess's Law?
The overall enthalpy change for a reaction is equal to the sum of the enthalpy changes for individual steps in the reaction
44
What is the equation for the Haber process?
3H2 (g) + N2 (g) ----> 2NH3 (g)
45
What is the standard enthalpy of formation?
Heat change when 1 mole of a compound is formed from its elements at a pressure of 1 atm
46
How do you calculate ΔH for standard enthalpy of formation?
Products - reactants
47
What is standard heat of formation?
Enthalpy change of formation of 1 mol of a substance in its standard state from its constituent elements in their standard state
48
What are the steps for calculating standard enthalpy of formation?
Write enthalpy of formation reaction | Add given rxns so that it gives desired rxn
49
What is bond breaking?
Endothermic
50
What is bond making?
Exothermic
51
What is bond dissociation energy?
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
What do exact values depend on?
Bond order + electronic environment of 2 atoms compromising the bond
53
How do you calculate bond enthalpies?
Reactants - products
54
What does it mean if the more oxidised a fuel is?
Less energy we can get from its combustion
55
What is a spontaneous process?
A process that, once started, proceeds on its own without a continuous external influence
56
When will a spontaneous reaction occur slowly?
If it has a high Ea
57
What is entropy?
The amount of molecular randomness in a system
58
When are spontaneous processes favoured?
Decrease in H (-ΔH) | Increase in S (+ΔS)
59
What is the equation for ΔS?
S final - S initial
60
What happens to entropy as order increases?
Decreases
61
What happens to entropy as disorder increases?
Increases
62
Describe entropy of solid, liquid + gas
Solid < liquid < gas
63
What is entropy?
Is the measure of how dispersed energy + matter is
64
What is change in entropy equal to?
The heat transferred reversibly to it, divided by the temp at which the transfer takes place
65
Is entropy a state function?
YES
66
What is the 2nd Law of Thermodynamics got to do with?
Entropy
67
Why is entropy reversible?
Equal temp at either side of thermally conducting walls
68
Why is entropy heat?
Because its random molecular motion | Work = ordered molecular motion
69
Why does entropy got to do with temperature?
Accounts for randomness of molecular motion
70
When is a given entropy change most significant?
For cold system
71
How do you calculate entropy of heating H2O?
ΔS = q rev/T
72
How do you calculate ΔS accompanying heating?
ΔS =C In (Tf/Ti) C = heat capacity of system Ti = initial temp Tf = final temp
73
What does it mean when Tf > Ti?
Log is positive = ΔS > 0 = what we would expect
74
When are entropy changes higher?
Things with high heat capacities
75
What are phase transitions accompanied by?
Entropy changes
76
Why does entropy increase in phase transitions?
Molecules are able to move more freely upon melting or boiling = increase entropy
77
How do you calculate entropy of vaporisation of H2O?
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
What is C p,m?
Molar heat capacity at constant pressure
79
What is 2nd Law of Thermodynamics?
The amount of heat passing to/from the surroundings is equal + opposite to the heat leaving/entering the system
80
How do you calculate entropy of surroundings?
ΔS sur = -ΔH/T
81
What is the main 2nd Law of Thermodynamics?
The entropy of the universe increases in spontaneous process + remains unchanged in an eqm process
82
What is the 3rd Law of Thermodynamics?
The entropy of a perfectly ordered crystalline substance at 0K is zero
83
What happens at a higher temp?
Greater molecular motion Broader distribution of individual molecular energies More randomness Higher entropy
84
What happens at lower temp?
Less molecular motion Narrower distribution of individual molecular energies Less randomness Lower entropy
85
What are absolute entropies equal to?
Absolute zero
86
What is standard molar entropy?
The entropy of 1 mole of a pure substance at 1 atm pressure + specified temp
87
What is the standard entropy of reaction?
The entropy change for a reaction carried at 1 atm + 25 degrees
88
When do processes occur spontaneously?
If overall entropy of universe increases
89
How do you calculate entropy of universe?
ΔS sys - ΔH/T | At constant temp + pressure
90
What is Gibbs Free Energy equation?
ΔG = ΔH - TΔS
91
What is the reaction at constant temp when ΔG < 0?
Spontaneous in forward direction
92
What is the reaction at constant temp when ΔG > 0?
Spontaneous in backwards direction
93
What is the reaction at constant temp when ΔG = 0?
Reaction at eqm
94
What is the ΔG of any process?
The max non-expansion work that can be extracted from process at constant temp + pressure
95
How do you calculate standard free energies of formation?
ΔG = products - reactants
96
How do you calculate ΔG under non-standard conditions?
ΔG = ΔG° + RT In K
97
How do you calculate ΔrG°?
-RT In K
98
What happens when a reaction mixture is mostly reactants?
K < 1 RT In K < 0 ΔG < 0 Total free energy decreases as reaction proceeds spontaneously in forwards direction
99
What happens when a reaction mixture is mostly products?
K > 1 RT In K > 0 ΔG > 0 Total free energy decreases as reaction proceeds spontaneously in backwards direction
100
What is Ki?
Inhibitor constant
101
What is ionic bond value?
20-40 kJ/mol
102
What is polarisation effects important for?
Soft atoms | eg. sulphur
103
What are dispersion effects important for?
Attractive component of van der Waals interactions
104
What is H bonding important for?
Angular dependence which produces directionality in binding
105
What is H bonding drug binding?
Thermoneutral
106
What do organic molecules want to do in aq environment?
Come together | = hydrophobic effect = form droplets
107
What is effective drug design?
Compromise between enthalpic + entropic considerations

Medicinal Chemistry (19 decks)

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