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3rd Year Fall > C2301 Final > Flashcards

C2301 Final Flashcards

1
Q

Thermodynamics

A

Describes a system at macroscopic scale with respect to its bulk properties

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2
Q

Volume

A

Amount of space an object occupies or enclosed in a container

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3
Q

Pressure

A

Force exerted by a gas per unit area on the walls of a container

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4
Q

Pressure Units (4)

A
  1. Pascal
  2. Bar
  3. Atm
  4. Psi
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5
Q

Temperature

A

Average translational kinetic energy of a sample of molecules

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6
Q

Adiabatic boundary

A

Prevents heat transfer

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7
Q

Boyle’s Law, Charle’s Law, Avogadro’s Principle

A

Boyle: PV constant at constant n,T
Charle’s: V=constant x T, at constant n,P
Same for P
Avogadro: V=constant x n, at constant P, T

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8
Q

Ideal Gas Law

A

PV=nRT

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9
Q

Isotherm

A

P vs. V at constant T

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10
Q

Isobar

A

V vs. T at constant P

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11
Q

Isochor

A

P vs. T at constant V

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12
Q

Surface Plots

A

A 3D plot of P vs. V vs. T.

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13
Q

Combined Gas Law

A

P1V1/n1T1=P2V2/n2T2

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14
Q

Thermodynamic System

A

region of the universe with defined boundaries with which we study

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15
Q

Open system

A

Exchange matter and energy with surroundings

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16
Q

Closed system

A

Exchanges only matter

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17
Q

Isolated system

A

cannot exchange energy or matter

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18
Q

Extensive variables

A

Physical properties of a substance which depend on the amount of material present

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19
Q

Intensive Variables

A

Independent of amount of material present

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20
Q

Examples of extensive variables

A

V, mass, n, heat capacity, H, U, S, G, A

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21
Q

Examples of Intensive Variables

A

T, hardness, boiling point, density, concentration

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22
Q

Properties of Ideal Gases (4)

A
  1. Particles are point masses with no volume
  2. Exert no attractive or repulsive force on each other
  3. Obey ideal gas law exactly
  4. Infinitely compressible
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23
Q

Properties of Real Gases (6)

A
  1. Particles have a finite volume (cannot be infinitely compressed)
  2. Exert attractive and repulsive forces on each other
  3. Closely obey PV=nRT at low pressure and high temps
  4. Boyle T: repulsive and attractive forces cancel and the gas obeys ideal gas law exactly.
  5. At high P and low T molecular interactions cannot be ignored.
  6. Can be liquefied using pressure
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24
Q

What forces dominate at low P

A

Attraction

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25
Q

2 Points to remember about attraction

A
  1. As molecules come closer, attraction increase and decrease the potential energy
  2. At further separation distances, repulsions increase in strength and increase the potential energy
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26
Q

What are the two specific terms to the van der Waals equation and what do they represent/correct for?

A

a: relative strength of attractive intermolecular forces; corrects for reduction in P due to IM forces
b: total effective volume per mole of gas; corrects for size of molecule

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27
Q

Observations from the vDw eqn (4)

A
  1. Ideal gas law does not work well for high pressures
  2. Observed pressures are less than ideal pressures — attraction dominaes
  3. vDw eqn describes well up to 100bar
  4. As P increases, vDw does not work well, but it works better than the ideal gas law
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28
Q

What is a characteristiv of the Redlich-Kwong equation?

A

Sqrt(T) term

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29
Q

What is characteristic of the Beattie-Bridgman eqn?

A

A and B constants

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30
Q

What series does the virial equation employ?

A

Power series

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31
Q

Vapour Pressure

A

equilibrium pressure of a vapour above its liquid or solid

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32
Q

Phase Diagrams

A

P vs. T; show co-existence curves in which states exist at which pressure and T

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33
Q

Name of the 3 co-existence curves in a phase diagram

A
  1. Fusion curve
  2. Vaporization curve
  3. Sublimation curve
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34
Q

Triple Point

A

Equilibrium between solid, liquid, and vapour phases

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35
Q

Critical point

A

The point of critical temperature and pressure

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36
Q

Supercritical fluid

A

A state beyond the critical point where no distinct phase exists between a gas and liquid.

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37
Q

Properties of SCF (5)

A
  1. Effuse through solids (gas)
  2. Solvent properties (liquid)
  3. Small changes in P or T elicit large changes in density
  4. High heat capacities and compressibilities
  5. Low viscosities
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38
Q

Examples of supercritical fluid applications (2)

A
  1. scCO2 reduction
  2. Caffeine extraction
  3. scH2O is a green solvent
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39
Q

Why do SCFs not form hydrogen bonds?

A

The molecules have too much translational KE such that the H bonds easily break.

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40
Q

Compressibility Factor, Z

A

Describe how large the errors are; i.e. how far does the ideal gas law deviate from the van der Waals

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41
Q

When does Z=1 for a real gas?

A

At the Boyle Temperature

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42
Q

What dominates when Z<1?

A

Attraction

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43
Q

What dominates if Z>1?

A

Repulsion

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44
Q

Why does N have a low Z at low pressure but high Z at high P (isothermal)?

A

At low P, T drops and molecules have less KE to overcome attraction; i.e. gas becomes more compressible and Z decreases.
At high P, V is small; molecules are closer together which increases repulsions and Z.

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45
Q

What are reduced variables?

A

The quantity divided by their critical value

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46
Q

Why are reduced variables used?

A

To create a generality that does not depend on the arbitrary constants in the VdW eqn.

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47
Q

What are the 2 parts of the Law of Corresponding states?

A
  1. All gases with the same reduced T and P are in corresponding states; should occupy same reduced volume.
  2. This is useful in predicting experimental behaviour. All gases in corresponding states should have same Z.
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48
Q

What are the 5 ways that internal energy is described?

A
  1. Translational KE
  2. PE
  3. Molecular vibrations/rotations
  4. E stored in chemical bonds
  5. PE of interactions between molecules
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49
Q

First Formulation of the First Law

A

The internal E of a system is constant

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50
Q

Second Formulation of the First Law

A

In a closed or isolated system with no chemical reactions, E can only flow with the exchange of heat and work.
dU=q+w

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51
Q

System

A

part of the world of interest

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52
Q

Surroundings

A

Region directly adjacent to the system

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53
Q

Heat

A

The amount of E that flows across a boundary between the system and surroundings because of a T difference

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54
Q

3 Ways heat is transferred

A
  1. Conduction
  2. Convection
  3. Radiation
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55
Q

Transitory

A

Only appears during a change of state of the system (not related to initial/final)

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56
Q

Work

A

Any action that transfers E across the boundary between system and surroundings

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57
Q

Energy

A

Capacity of a system to do work

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58
Q

What quantities are transitory?

A

Heat and work

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59
Q

What quantity is non-transitory?

A

Energy

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60
Q

Reversible Process

A

System and environment can be restored to the same initial conditions from before the process occurred.

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61
Q

Irreversible Process

A

System and environment cannot be restored to their original states

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62
Q

Path Function

A

Depends on the path taken to arrive at the systems present state

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63
Q

State Functions

A

Pathway independent and have values determined by the state of the system

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64
Q

Boltzmann Distribution

A

Relative probability of finding a molecule/atom/electron in a specific energy state

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65
Q

Degrees of Freedom

A

Number of variables needed to describe motion of a particle completely

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66
Q

How many degrees of freedom for translational motion?

A

3 (x,y,z)

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67
Q

How many degrees of freedom for rotational motion?

A

2 (linear) or 3 (nonlinear)

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68
Q

Degrees of freedom for vibrational motion

A

Linear: 3N-5
Non-Linear: 3N-6

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69
Q

What are the 2 common experimental conditions to investigate with heat and what are they called?

A

Heat at constant P, qp, enthalpy
Heat at constant V, qV, internal energy

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70
Q

Heat Capacity

A

The measure of E needed to change the T of a substance a given amount (material and T dependent)

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71
Q

Shomate Equation

A

Describes the heat capacity of a substance at a specific T using curve fitting.

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72
Q

What is the relation between Cp and Cv for an Ideal Gas?

A

Cp=Cv+R

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73
Q

Why is Cp>Cv for gases?

A

At constant P, gas expands as T increases, and system does work on surroundings. As a consequence, not all of the heat flow into the system is used to increase dU. No work occurs at Cv, and all heat is used to increase dU.

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74
Q

What is the relation between Cp and Cv for liquids and solids?

A

Cp is approximately equal to Cv

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75
Q

Endothermic Process

A

heat flows into system from surroundings

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76
Q

Exothermic Process

A

heat flows out of system into surroundings

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77
Q

Define enthalpy

A

Enthalpy is the heat transfer by a system for a process occurring at constant P.

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78
Q

Internal Energy relation to Cv

A

dU=qv=CvdT

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79
Q

Enthalpy relation to Cp

A

dH=qp=CpdT

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80
Q

What is an assumption made when related enthalpy to Cp?

A

They are only valid if no chemical reactions or phase changes occur

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81
Q

Reversible adiabatic compression of a gas leads to heating or cooling?

A

Heating

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82
Q

Reversible adiabatic expansion of a gas leads to heating or cooling?

A

Cooling

83
Q

Thermochemistry

A

Branch of thermo concerned with heat flow into or out of a reaction system

84
Q

What do we consider E stored in chemical bonds?

A

Potential E

85
Q

What are standard state conditions?

A

1atm, 25C, 1M

86
Q

Standard Enthalpy of Reaction

A

Refers to the reaction of 1 mol of specified reaction at standard state

87
Q

Standard Enthalpy of Formation

A

Enthalpy change of a reaction in which only 1 mol of the species of interest, with only pure elements in their most stable state are reactants, under standard state conditions.

88
Q

Generalized enthalpy reaction of the following equation:
aA+bB = cC+dD

A

drH=c(dfH C)+d(dfH D) - a(dfH A) - b (dfH B)

89
Q

Hess’s Law

A

The enthalpy change for any sequence of chemical reactions that sum to the overall reaction is the sum of the enthalpies of each individual reaction step.

90
Q

Reaction Enthalpies not at Standard State

A

dH(T)=dH(298.15K)+ int(dCp(T))dT

91
Q

What is constant during bomb calorimetry and what is measured?

A

Constant volume, dU

92
Q

What is the main use for bomb calorimetry?

A

Determining the caloric content of food

93
Q

How is the calorimeter constant determined in bomb calorimetry?

A

Use of a standard of known molar enthalpy of combustion, usually benzoic acid

94
Q

Equation to calculate dH in bomb calorimetry (assuming we have already calculated dU)

A

dcH=dcU+d(PV)

95
Q

What is another name of the constant pressure calorimeter?

A

Coffee-cup calorimeter

96
Q

What type of enthalpy reactions are typically studied in constant pressure calorimetry?

A

Solvation

97
Q

List the name of all phase changes.

A
  1. Melting: s - l
  2. Freezing: l - s
  3. Vaporization: l - g
  4. Condensation: g - l
  5. Sublimation: s - g
  6. Deposition: g - s
  7. Ionization: g - p
  8. Recombination: p - g
98
Q

How is the enthalpy of sublimation related to the other enthalpies of phase changes?

A

dsubH=dmeltH+dvapH

99
Q

What variable represents the isobaric volumetric thermal expansion coefficient and what is it equal to?

A

alpha, a=(1/V)(dV/dT)

100
Q

What is the name of the variable kappa_T and what is the equation?

A

Isothermal compressibility,
kappa_T=(-1/V)(dV/dP)

101
Q

Relation of partial differentials to exact differentials

A

Let b represent the symbol for a partial differential.
df=(bf/bx)dx+(bf/by)dy

102
Q

How can the internal energy be written in terms of differentials (not necessarily exact)?

A

dU=d-q+PextdV
where d-q is an inexact differential

103
Q

Relation of heat capacity at constant volume

A

dU/dT=Cv

104
Q

What is the name of the relation defined by:
dU/dV=T(dP/dT)-P

A

Internal Pressure

105
Q

Joule Experiment

A

Attempted to measure dU/dV for an ideal gas.

106
Q

Joule experiment setup

A

Two interacting systems in a rigid adiabatic enclosure, with system 1 being the water bath and 2 being the volume within 2 vessels.

107
Q

Joule-Thomson experiment

A

Seeks to measure dH/dV, far more accurate than the Joule experiment

108
Q

Joule-Thomson experiment setup/process

A

Gas at initial P,V,T conditions flows from a high P cylinder into a low pressure cylinder. Gas is forced through a porous plug in which piston moves to maintain a constant P in each region. This causes a P drop across the plug and the T change is measured.

109
Q

What is the name of a process occurring at constant enthalpy?

A

Isenthalpic

110
Q

What is u_J-T?

A

Joule-Thomson coefficient
Limiting ratio of dT and dP

111
Q

What dominates at positive u_J-T?

A

Attraction

112
Q

What dominates at negative u_J-T?

A

Repulsions

113
Q

What is the temperature at which the Joule-Thomson coefficient is 0?

A

Inversion Temperature

114
Q

What approximation can be made for U and H for solids and liquids?

A

They can be considered a function of T alone

115
Q

What is the direction of evolution of a system known as?

A

Spontaneous direction

116
Q

What are the 2 formulations of the 2nd law?

A
  1. It is impossible for a system to undergo a cyclic process that turns all heat completely into work done on the surroundings.
  2. It is impossible for a process to occur that has the sole effect of removing a quantity of heat from an object at a lower T and transferring it to an object at a higher temperature.
117
Q

Classical definition of entropy

A

Entropy is the amount of work not available to do work

118
Q

What is the entropy for a cyclic process that is entirely reversible, and is this feasible?

A

dS=0, not feasible

119
Q

Equation definition of entropy

A

dS=dqrev/T

120
Q

Formal definition of the 2nd law

A

For any process proceeding in an isolated system, there is a unique direction of spontaneous change and dS>0 for the spontaneous process.

121
Q

Is expansion of compression spontaneous?

A

Expansion

122
Q

What is the equation representation of entropy for phase changes?

A

dvapS=dvapH/Tvap

123
Q

Statistical definition of entropy

A

Measure of the degree to which energy is dispersed into the available E levels associated with random molecular motion.

124
Q

Point

A

E spreads out more easily when the energy gap between adjacent levels is small.

125
Q

Single particle microstate

A

Any particular E state of a single molecule; quantized unit combined trans, rot, and vib E states

126
Q

N-particle microstate

A

Any quantized state of a whole system of molecules. Collection of single particle microstates.

127
Q

What are the 5 rules for entropy and the number of N-particle microstates?

A
  1. At any given instant in time, total E of the system is dispersed throughout one N-particle microstate.
  2. In the next instant in time, total E is dispersed throughout a different N-particle microstate of equal energy
  3. Each accessible equal E N-particle microstate is equally possible
  4. Number of single particle microstates is large, the number of N-particle microstates is enormous
  5. Under a given set of conditions, the number of accessible N-particle microstates is the number of ways its thermal E can be dispersed among the different E levels of all its molecules
128
Q

What is the Ludwig Boltzmann entropy equation?

A

S=kBln(omega)

129
Q

If dS is positive, the system has changed from:

A

smaller number of N-particle microstates to larger number of N-particle microstates

130
Q

As T increases, molecules have more energy and can populate higher E levels, causing:

A

Increase number of accessible N-particle microstates

131
Q

What is the condition for entropy decrease in a system?

A

dStotal>0

132
Q

Any process that occurs in the universe is spontaneous and leads to an increase of Stotal. What is this concept often referred to as?

A

TIme’s Arrow

133
Q

3rd Law of Thermodynamics

A

The entropy of a pure, perfectly crystalline substance is 0 at 0K.

134
Q

What is the number of microstates in a perfectly crystalline substance?

A

1

135
Q

Residual entropy

A

Entropy at 0K for crystals that are not perfectly crystalline

136
Q

What is the significance of entropy changes in chemical reactions?

A

They are important in determining equilibrium concentrations in a reaction.

137
Q

How do absolute entropies differ from enthalpies?

A

Entropies of pure substances are not zero in their reference state.

138
Q

What is the cyclic process in heat engines? (4 steps)

A
  1. Fuel intake
  2. Ignition and expansion
  3. Exhaust
  4. Compression
139
Q

Can heat or work be entirely converted to the other?

A

Work

140
Q

Does compression or expansion determine the max work for a reversible process?

A

Expansion

141
Q

What is a carnot plot and how can it be used to determine the work of the cycle?

A

Cyclic plot of P vs. t of each of the 4 steps (isothermal compression, adiabatic expansion, isothermal expansion, and adiabatic compression). The area of the plot is the work done by the cycle.

142
Q

What is the efficiency of a Carnot cycle?

A

Ratio of work output to the heat withdrawn from the reservoir.
e=-wcycle/qab

143
Q

What is the work for each segment of the Carnot cycle (ideal gas)

A

Expansions: w<0
Compressions: w>0

144
Q

The Clausius Inequality

A

TdS>=dq (reversible)
dS>dq/T (irreversible)

145
Q

Hemholtz Energy

A

A=(U-TS)
Total exapansive and non-expansive work (total max work)

146
Q

What is the formula for change in Hemholtz E?

A

dA=dU-TdS

147
Q

Gibb’s Energy

A

Total maximum non-expansive work possible.

148
Q

When is a system at equilibrium?

A

dA=0

149
Q

When is GIbb’s E spontaneous?

A

dG<=0

150
Q

Summarize: what do each of U, H, A, and G measure?

A

U: all kinetic and potential E.
H: heat flow into or out of system.
A: maximum total work a process can generate.
G: maximum non-expansive work a process can generate.

151
Q

Summary of equations for U, H, A, and G (non-differential)

A

U=q+w
H=U+PV
A=U-TS=H-PV-TS
G=H-TS=U+PV-TS

152
Q

Summary of equations of U, H, A, and G (differential form)

A

dU=tdS-PdV
dH=TdS-PdV+PdV+VdP=TdS+VdP
dA=TdS-PdV-TdS-SdT=-SdT-PdV
dG=TdS+VdP-TdS-SdT=-SdT+VdP

153
Q

What quantities is each of U, H, A, and G dependent on (a result of the differential equations)

A

U (S,V)
H (S,P)
A (T,V)
G (T, P)

154
Q

Maxwell relations (briefly explain)

A

State how U, H, A, and G vary with their natural state variables.

155
Q

Does G increase or decrease with increase in T and P?

A

Decreases with increase in T, increase with increase in P

156
Q

Chemical Potential

A

Change in Gibbs E of a mixture per mole of substance added at constant concentration.
Or, the chemical potential is the tendency of the system to donate a particle.

157
Q

What is the Gibbs E of mixing?

A

Gfinal-Ginitial

158
Q

What is the entropy of mixing?

A

dmixS=-dmixG/dT

159
Q

What is the enthalpy of mixing?

A

dmixH=dmixG+TdmixS

160
Q

What is the extent of reaction?

A

The number of moles the reaction is allowed to proceed to the right

161
Q

What is the name of the conditions where the differential of Gibbs E of reaction in respect to the extent of reaction is 0?

A

Equilibrium position

162
Q

In a simple reaction, what are the two contributions to Gibbs E?

A
  1. Unmixed substances
  2. Mixing
163
Q

For what conditions does the differential of the Hemholtz E in respect to the extent of reaction equalling 0 correspond to an equilibrium position?

A

Constant V and T

164
Q

Relation of Gibbs E and equilibrium constant

A

drG=-RTlnQp

165
Q

What is the relation between Qp and Kp?

A

Kp is the special case of Qp where the reaction is at equilibrium and is called the thermodynamic equilibrium constant

166
Q

Chemical Kinetics

A

Study of the rates and mechanisms of chemical reactions

167
Q

Reaction Rate

A

Change in the extent of reaction with time

168
Q

Rate of Reaction

A

in respect to the change in the number of moles of a given species with time

169
Q

What must be assumed to discuss rate laws?

A

The reaction is homogeneous

170
Q

True or False: the reaction order is related to stoichiometric coefficients.

A

False

171
Q

How must all rate laws be determined?

A

Experimentally

172
Q

Rate constant, k

A

Proportionality constant between the concentrations of reactants and the reaction rate.

173
Q

General formula for the units of a rate constant in relation to the overall order, n

A

M^(1-n)s-1

174
Q

What are the 2 methods for determining reaction orders? Briefly describe each.

A
  1. Isolation method: all reagents are provided in excess but one. The order with respect to that reagent can be determined.
  2. Method of Initial Rates: the concentration of a single reagent is changed while all others are held constant and initial rate is determined.
175
Q

How do we measure the rate of a reaction? (2 categories)

A
  1. Chemical methods: chemical rxn initiated and periodically samples are taken out of rxn mixture and manipulated to terminate the rxn.
  2. Physical methods: a physical property of the system is measured/monitored as the rxn proceeds.
176
Q

Reaction mechanism

A

Collection of individual kinetic processes or elementary steps involved in the transformation of reactants to products.

177
Q

Elementary reaction steps

A

Single steps and a pathway/mechanism may contain one or more of these

178
Q

Molecularity

A

Stoichiometric quantity of reactants involved (i.e. unimolecular has 1 reactant, bimolecular has 2, etc.)

179
Q

When are the order and molecularity equivalent?

A

For elementary reaction steps

180
Q

Integrated rate law expressions

A

Provide a predicted temporal evolution of the reactant/product concentrations that can be used in lieu of known rate expressions.

181
Q

How can a first order rate law be expressed? (Choose linearly convenient form)

A

ln[A]=ln[A]0-kt

182
Q

Half-Life

A

time for reactant concentration to decrease to half its initial value.

183
Q

Half-life for first order equation?

A

t1/2=ln2/k

184
Q

What is half life independent of?

A

Initial concentration

185
Q

Second Order Type 1 Reaction

A

A reaction that is second order with respect to 1 reactant.

186
Q

Second Order Type 2 Reaction

A

A reaction with 2 reactants that is 2nd order overall but first order with respect to each reactant.

187
Q

What is the rate law for second order type 1?

A

1/[A]=1/[A]0+kefft

188
Q

What is the effective rate constant?

A

keff=2k. Used for Second order type 1 reactions.

189
Q

Half-life for second order type 1

A

t1/2=1/keff[A]0

190
Q

Why are second order reactions dependent on [A]0?

A

Bimolecular reactions are dependent on the number of successful collisions taking place.

191
Q

Rate law for second order type 2

A

1/[B]0-[A]0*ln([B]/[B]0/[A]/[A]0)=kt

192
Q

What is the half life for second order type 2 reactions?

A

Concept of half-life does not exist.

193
Q

Sequential First Order Reactions

A

Reactions that occur in a series of steps in which reactants are transformed into intermediate species until achieving a stable product

194
Q

Intermediate

A

A product of one sequential step that is consumed in another

195
Q

Maximum Intermediate species concentration eqn

A

tmax=(1/KA-kI)*ln(kA/kI)

196
Q

Rate determining step

A

If one step is significantly slower than the other, it determines the rate of reaction

197
Q

Euler’s Method in the Steady State Approximation

A

Determines the concentrations numerically as a function of time

198
Q

Steady state approximation

A

When intermediate reactions are rapid, very little intermediate species will be detected in solution. Thus, the concentration of intermediate with respect to time can be considered 0.

199
Q

When is the steady state approximation valid?

A

When the intermediate decay rate is greater than the rate of production

200
Q

Yield (Kinetics)

A

Probability that a given product will be formed by the decay of the reactant

201
Q

Arrhenius Expression

A

k=Ae^-Ea/RT

202
Q

Graphical form of Arrhenius equation

A

ln(k)=ln(A)-Ea/RT

203
Q

Apparent rate constant eqn

A

kapp=kA+kB

204
Q
A

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