Quiz 3 Flashcards
1
Q
Potential Energy
A
Energy an object has by virtue of its placement in a field of force, like gravity
2
Q
PE = ?
A
mgh
3
Q
Kinetic Energy
A
Energy an object has by virtue of its motion
4
Q
KE = ?
A
1/2mu^2 and 3/2RT
5
Q
When KE is at max, PE is at _____
A
minimum
6
Q
When PE is at max, KE is at _____
A
minimum
7
Q
Internal (total) energy =
A
KE + PE
8
Q
Types of molecular kinetic energy
A
Translation, rotation, vibration
9
Q
Translation
A
Motion through space
10
Q
Rotation
A
Motion about the center of mass
11
Q
Vibration
A
Motion directed through chemical bonds
12
Q
In a molecule, where is PE stored?
A
Bonds
13
Q
Electrostatic
A
Intermolecular attractions - molecule interacts with neighboring molecules
14
Q
Thermodynamics
A
Study of energy and its interconversion
15
Q
How can energy be transferred?
A
As heat or work
16
Q
Heat (q)
A
Net transfer of energy between objects due to temp gradient
17
Q
Work (w)
A
Force (energy) acting over a change in h/d to move an object
18
Q
ΔE =
A
q+w
19
Q
What does E describe?
A
The state of the system
20
Q
When does the state of a chemical system change?
A
When the system exchanges energy as heat or work
21
Q
Surroundings
A
Everything around the system
22
Q
First law of thermodynamics
A
The total energy of the universe is constant
23
Q
What direction does energy flow?
A
High E concentration to low E concentration
24
Q
Exothermic Process
A
Evolution of system that results in heat transfer to surroundings q<0 (heat lost)
25
Endothermic Process
Evolution of system that results in heat transfer to system q>0 (heat gained)
26
Expansion
Vf > Vi and ΔV > 0 and w < 0
27
Compression
Vf < Vi and ΔV < 0 and w > 0
28
Work done on system by surroundings =
+w
29
Work done on surroundings by system =
-w
30
Heat/work in
+q and +w
31
Heat/work out
-q and -w
32
Pressure-volume work (PV)
Expansion of a gas against a constant external pressure
33
State functions/variables
Describe the momentary condition of thermodynamic system or difference between two momentary conditions
34
Examples of state functions/variables
E, ΔE, T, P, V, n, KE, PE
35
Process/path funcitons
Describe the energy change associated with a particular process imposed on a thermodynamic system
36
Examples of process/path functions
q and w
37
Do state function depend on the path the system takes?
No
38
Increase in system temp =
Increase in system's heat energy content
39
What happens if heat is added at constant volume?
T and P increase
40
Is there work when V is constant?
No
41
What is the heat flow measured under constant P conditions?
ΔH
42
Which R value do you use for molar heat capacity?
8.314
43
Molar heat capacity (ΔE) definition
Energy required to raise the temp of 1 mole of substance by 1K
44
What happens if heat is added at constant pressure?
T and V increase
45
What is the heat flow measured under constant V conditions?
ΔE
46
Molar heat capacity (ΔH) defintion
Enthalpy required to raise the temp of 1 mole of substance by 1K
47
Is work done at constant pressure?
Yes
48
Molar heat capacity definition
Energy required to raise the temp of 1 mole of a substance by 1K
49
How do we go from Cv to Cp?
Add 1R
50
For a polyatomic ion, are Cv and Cp greater than or less than Cv and Cp for a monatomic ion?
Greater
51
Is losing heat exothermic or endothermic
Exothermic
52
Isochoric
Constat Volume
53
Isobaric
Constant Pressure
54
Isothermal
Constant Temperature
55
When do we use the 101.3 J/L*atm conversion factor?
When going from L*atm to Joules
56
Hess's Law
Going from one set of reactants to one set of products, overall change in enthalpy is the same (doesn't depend on number of steps)
57
Can we measure absolute enthalpies
No
58
Calculate thermodynamics for compounds
Pure substance its normal phase at P = 1atm
59
Calculate thermodynamics for solutions
Concentration of 1M
60
Calculate thermodynamics for elements
The most stable form of the element at P = 1atm
61
What subscript is used for standard state
º
62
Standard enthalpy of formation (ΔHfº)
Enthalpy change that accompanies the formation of one mole of a compound from its elements with all substances in their stand states at 25ºC
63
Spontaneous Process
Will occur in a system left to itself; no action from the surroundings is necessary to drive the process
64
Non-spontaneous Process
Requires action from the surroundings to occur
65
Second Law of Thermodynamics
The entropy of the universe is always increasing
66
Are processes that lead to an increase in the entropy of the universe spontaneous or non-spontaneous
Spontaneous
67
Configuration
General arrangement of a system, which can be achieved by one or microstates
68
Microstate
Specific arrangement of a system corresponding to a particular configuration
69
Weight (omega)
Number of microstates associated with a given configuration
70
Entropy
Change in the arrangement of energy in response to a heat flow at a given temp
71
What does rev mean in qrev?
Reversible (q flows very slow)
72
ΔS (universe) > 0
Spontaneous
73
ΔS (universe) < 0
Spontaneous in opposite direction
74
ΔS (universe) = 0
At equilibrium
75
Third Law of Thermodynamics
The entropy of a perfect crystal at 0 K is 0
76
Standard Molar Entropy (S°)
Entropy change associated with heating one mole of a substance from 0 K to 298 K at 1 atm
77
Entropy in exothermic process
ΔS (surroundings) > 0
78
Entropy in endothermic process
ΔS (surroundings) < 0
79
Entropy from gas to liquid
ΔS (system) < 0, ΔH (system) < 0, ΔS (surroundings) > 0
80
Entropy from liquid to gas
ΔS (system) > 0, ΔH (system) > 0, ΔS (surroundings) < 0
81
Do gases contract or expand at low T?
Contract
82
Do gases contract or expand at high T?
Expand
83
ΔG<0
Spontaneous
84
ΔG>0
Spontaneous in opposite direction
85
ΔG=0
Equilibrium
86
When does the spontaneity of a rxn change?
After/before equilibrium
87
When are exothermic rxns with ΔS<0 spontaneous (-ΔH and -ΔS) ?
At low temps
88
When are exothermic rxns with ΔS>0 spontaneous (-ΔH and +ΔS) ?
At all temps
89
When are endothermic rxns with ΔS>0 spontaneous (+ΔH and +ΔS) ?
At high temps
90
What controls spontaneity when Tactual > X
ΔS
91
What is X?
Temp at which spontaneity changes
92
What controls spontaneity when Tactual < X
ΔH
93
Tactual = X
Equilibrium
94
Spontaneity when -ΔS and -ΔH
At low temps
95
Spontaneity when +ΔS and -ΔH
All temps
96
Spontaneity when +ΔS and +ΔH
High temps
97
Spontaneity when -ΔS and +ΔH
No temps (never spontaneous)
98
Standard Free Energy Change (ΔG°rxn)
Free energy change when reactants and products are in their standard state
99
Standard Free Energy of Formation (ΔG°f)
Free energy change that occurs in the formation of 1 mol of a substance in its standard state from elements in their standard state
100
If temperature is -Kelvin, what does that mean about the spontaneity?
Rxn is spontaneous at all temps
101
What is ΔG ?
Free energy change for rxns occurring at any temp or concentration
102
Whatis ΔG° ?
Change in free energy for a rxn involving compounds in their standard states
103
If ΔG° < 0 then _____
K > 1
104
If ΔG° = 0 then _____
K = 1
105
If ΔG° > 0 then _____
K < 1
