2nd Exam Review - Idaho State University

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Exam Review

Review for Chapters 1, 6, 8, & 21

Definitions: (The meanings of these words and phrases should be very familiar to you!)

System State of the System

Processes Surroundings

Macroscopic System

Open System

Isolated System

Closed System

Adiabatic

Reversible Process

Irreversible Process

Isothermal

Isochoric

Macroscopic System

Thermodynamic State

Equilibrium State

Ideal Gas Law

Kinetic Theory of Gases

Isobaric

Isenthalpic

Microscopic System

State Functions or State Variables

SI Units

Functions

Dependent Variable

Equation of State

Daltons Law of Partial Pressures

Supercritical Fluid

Coefficients

Independent Variable

Extensive Variable

Intensive Variable

Simple System

Boyle Temperature

Triple Point

Normal Melting Temp. (Point)

Normal Boiling Point

Critical Point

Isotherms

Reduced Variables

Internal Energy

Partial Derivative

Gibbs Phase Rule

Phase Transitions

Coexistence Curve

Normal Freezing Point

Normal Sublimation Temp.

Critical Constants

Gibbs Phase Rule

Kinetic Energy

Potential Energy

Thermodynamic Energy

Boltzmann Distribution

Probability Distribution

Identity for Change of Variables

Average Values (like average speed) Assumptions for Kinetic Theory

Calculations: (you should be familiar with the following in terms of calculations)

Van der Waals Eqn. of State Relation between molar volume and density

Multiplication Rule for Derivatives

Virial Equation of State

Compression Factor Z

Ideal Gas Law and Daltons Law

Deriving Eqns. from the Ideal Gas Law

Virial Coefficients

Compressibility of Liquid vs Gas

Critical Points from Eqn. of State

Pressure Volume Curves Pressure Temperature Curves

Calculation of Degrees of Freedom from Phase Rule

Pressure as a Function of Molar Volume at Various Constant Temp. Values

Review for Chapters 2 and 3

Definitions: (The meanings of these words and phrases should be very familiar to you!)

System Work

External Pressure

Reversible

Exactness

Heat

Standard State

Inexact Differential

Criteria for Exactness

Specific Heat

Heat Capacity

Calorimeter Constant

Law of Conservation of Energy

Isothermal

Isobaric

Reversible

Isolated System

1st Law of Thermodynamics

Closed System

Isochoric

Adiabatic

State Variable

Path Dependent

Expression for dH for Ideal Gas

Expression for dU for Ideal Gas

Molar Internal Energy

Exothermic

Hess' Law

Kirchoff's Law

STP (Standard Temperature and Pressure)

Isenthalpic

Internal Energy

Enthalpy

Endothermic

Enthalpy of Formation

H= U + PV dU = dq + dw

Cpm = Cvm + R

Bomb Calorimeter

Joule Thompson Coefficient

Cp = Cv + nR

Enthalpy of Combustion

Average Bond Energies

Permuter

Inverter Isothermal compressibility

Expressing U in Terms of Heat and Work

Use and/or derivation of Expressions for Work, Heat, Enthalpy etc of adiabatic, reversible, isothermal etc. process

Calculations with a Constant External Pressure

Calculations with a External Pressure in Equil with Internal Pressure

Use of 1st Law to Test for Allowedness of a Process

Dependence of Enthalpy on Temperature

Use of Heat Capacity to Determine the Enthalpy Change

Calculation of dH and dU from Heats of Formation, Heats of Combustion, i.e. from Hess' Law

Expression for dH and dU for ideal gas

Converting between H and U

Exactness

Relation of Exactness and State Function

Manipulation of partial derivatives with the Permuter, Inverter, Exactness, etc. giving new

Thermodynamic Expressions

The use of the Joule Thompson coefficient to determine if a substance can be used as a coolant

2

nd

Exam Review

Definitions: (The meanings of these words and phrases should be very familiar to you!)

1st and 2nd Laws of Thermodynamics Carnot Heat Engine & Assumptions dS = dq rev

/ T

State Function dS > dq

S irr

/ T rev cycl

=

 surr

State Variable cycle

dq re

/T = 0 Entropy is a State Function dS > 0 (irr adiabatic)

S = k ln W

Efficiency

Steady State

Absolute zero

Coefficient of Performance

Absolute Entropy

Troutons Rule

Heat Pump

Standard State for Entropy

G = H - TS

Claussius Inequality

Spontaneity

3rd Law of Thermodynamics

Refrigeration

Spontaneous

A = U-TS

Gibbs Energy of Reaction

Criteria, based on System Variables, for

H = U + PV

How does the entropy change as a function of temperature for a constant pressure or constant volume process (ideal gas) What is the expression for the entropy change of a constant pressure process which goes through several changes of state? In any irreversible process the entropy of the universe increases. Because entropy is a state variable, the entropy change of the system can be calculated using a reversible process having the same initial and final states as the irreversible process. In any reversible process the entropy of the universe remains constant and therefore this constitutes the minimal or maximal work case.

The Carnot efficiency tells about the maximum efficiency realizable for a process which converts heat to work. Know what the coefficient of performance is and how it related to give the work necessary in refrigeration or for a heat pump. The expression for the

Second Law of Thermodynamics  S tot

> 0 for an irreversible process is strictly applicable to the system and the surroundings. HOWEVER, new thermodynamic state variables, named the Helmholtz Free Energy and Gibbs Free Energy, were defined which determine the spontaneity of a process based on the system properties and the mechanical variables. Thus (dA)

T,V

< 0 and (dG)

T,p

< 0

(closed; PV).

Which property tells about the max non PV work? Which tells about the maximum amount of work the system can do?

Calculations: (These types of problems should be workable)

Use of the 2nd Law to test if a process is realizable (spontaneous).

General procedure for calculating entropy change in a closed system.

Calculation of entropy changes for processes that include phase transitions

Calculation of the Carnot efficiency.

Calculation of the Standard Entropy Change for a chemical reaction.

Calculation of the Entropy change for many types of processes.

Specification of the sign of the entropy change for a process.

Calculation of the Standard Gibbs Energy of Reaction

Derivation of Equations used to calculate the entropy changes for various processes.

Definitions: (The meanings of these words and phrases should be very familiar to you!)

1 st

and 2 nd

Laws of Thermodynamics Chain Rule and Product Rule

Fundamental Eqn. of Thermodynamics Gibbs Free energy

Maxwell Relation

Fugacity

Fugacity coefficient

Gibbs-Helmholtz eqn.

Defining Equation for the fugacity

Chemical Potential

Exact Differential

Standard State molar Gibbs Free Energy dU = TdS - PdV

Pressure Dependence of G

Natural Thermodynamic Variables for U,H,G, & A

Calculations: (you should be familiar with the following in terms of calculations)

Relation of Exactness and State Function to Deriving Maxwell’s Relations

Use of the Combination of 1 st and 2 nd Laws to find other Thermodynamic Relationships

Manipulation of Thermodynamic relations using partial derivative identities

Calculations to find

G at a different temperature

Calculations to find

G at a different pressure

Coming up with a value for the fugacity given the pressure.

Sketch of the graphs of the molar Gibbs Free energy as a function of the Pressure and

Fugacity

Use of the definition of the Chemical Potentials

Expression for the molar Gibbs free energy of a gas

Expression for the Fundamental Eqn of Chemical Thermodynamics or an open system.

General:

Know how the expression for the Fundamental Equation of Thermodynamics. It is essentially a combination of the 1st and 2nd Laws. Remember it was derived based on a reversible process, but is it applicable to any process within the restrictions of its derivation? What are the best thermodynamic variables for U? Be able to show how more Thermodynamic information comes from the definition of the exact differential and the exactness criterion. What are Maxwell’s relations?

How are they derived from the equation for dU? What about dG? What are the natural thermodynamic variables for dG? Be able to write out dG for these variables?

These variables are derived from the basic definition of G=H-TS. What is the Maxwell relation derived from dG?

G sys

tells us about the spontaneity of the process, and whether the system is at equilibrium. How does it change with P and T? What is the

Gibbs Helmholtz relation? Be able to use it. Does the Gibbs free energy change very

much with a pressure change on a solid or liquid? Why?

What is the fundamental equation of chemical thermodynamics? The chemical potential of a pure substance is (

G/

 n) p,T

and for a perfect gas

=

 o

+ RT ln(p/p o

) how does this change for a real gas. In general

=

 o

+ RT ln a where a is the activity. For ideal gas a = p/p o . For real gas a = f/p o . What is the fugacity coefficient? What is this eqn., f=

 p. Not only does the chemical potential show how G changes when the composition changes but also H and A when the appropriate thermodynamic variables are held constant. What needs to be held constant? Does the name chemical potential fit?

Definitions: vapor pressure phase boundaries pressure condensed phase critical point

Clapeyron Eqn. phase diagram triple point

Clausius Clapeyron partial vapor

Solid normal boiling point fluid p = p

* exp(V m

(l)

P/(RT)) (d

/dP)

T

= V m

Liquid

(d

/dT)

P

= -S m

Gas normal melting pt. standard freezing pt. supercritical

Know how the chemical potential or the Gibbs Free energy behaves before a phase change, during the phase change and afterward. How does the chemical potential vary with pressure?

How does the chemical potential vary with temperature. Why does the chemical potential of a pure substance decrease as the temp is raised. Be able to explain how the boiling pt of a pure substance increases with increasing pressure using a

vs T diagram and the fact that (d

/dP)

T

= V m

and V m

is much higher for a liquid than a solid. Why can an ice skater skate on H

2

O ice but not “dry” ice.

You should know how to find the location of phase boundaries since at equilibrium, their chemical potentials will be equal. This can be used to derive the Clapeyron Eqn. The general Clapeyron equation tells us the slope of the phase boundary at any point, and can be made more specific depending on the type of phase boundary.

You should be able to derive the Clapeyron equation that describes the specific case of a liquid-vapor, or solid-vapor boundary. What are the assumptions?

Calculations

P, T phase diagram p = p

* exp(V m

(l)

P/(RT))

(d

/dP)

T

= V m

and (d

/dT)

P

= -S m

Clapeyron Eqn

Claussius Clapeyron Eqn

Exam 3 Review

The exam will cover mainly Chp.5,6,7. The following review guide should give you an

idea of what to expect on the exam. The format of the exam will follow that of the previous exams, some multiple choice or true false followed by a problem section.

Terminology

Chp. 5

Partial Molar quantity

Gibbs Duhem Eqn.

Thermodynamics

Std. Chemical Potential

Partial Molar volume

Fundamental Eqn. of Chemical

Raoults Law

Ideal Solution

Thermodynamics of Mixing

Henry’s Law

Ideal Dilute Solution positive deviation from Raoults Law Negative deviation form Raoults Law

Excess Thermodynamic Functions

- interaction parameter boiling pt. elevation

Regular Solution

Colligative properties freezing pt. depression

Boiling pt. constant

Osmosis activity in terms of molality activities of ions

Debye Huckel Limiting Law

Ionic strength

Activity solute activity chemical potential of solvent

Freezing pt. constante

Osmotic Pressure

Activity coefficient solvent activity chemical potential of solute

Margules Eqns. mean activity coefficient extended Debye-Huckel law

Chp 6

Gibbs Phase Rule phase variance, degrees of freedom ` partial pressure of components isopleth temperature-composition diagram fractional distillation theoretical plates high boiling azeotrope immiscible liquids upper critical solution temp. eutectic composition incongruent melting liquid crystals zone levelling

Chp 7. extent of reaction exergonic rxn. component phase diagram vapor pressure diagram lever rule tie line simple distillation steam distillation azeotrope low boiling azeotrope partially miscible liquids lower critical solution temp. congruent melting peritectic line zone refining reaction Gibbs energy endergonic rxn.

std. Gibbs free energy of reaction reaction quotient thermodynamic equilibrium constant dissociation

K x

, K

P

, K

, K b

or K m van’t Hoff Eqn.

Ellingham diagram equilibrium equilibrium constant degree of dissociation, fractional

Le Chatelier’s Principle

Extraction of metals from oxides

BACKGROUND INFO

The chemical potential of a pure substance is (dG/dn) p,T

and for a perfect gas

=

 o

+ RT ln(p/p o

) how does this change for a real gas. In general

=

 o

+ RT ln a where a is the activity. For ideal gas a = p/p o . For real gas a = f/p o . What is the fugacity coefficient f=

 p. Not only does the chemical potential show how G changes when the composition changes but also H and A when the appropriate thermodynamic variables are held constant. What needs to be held constant? Does the name chemical potential fit?

Know how the chemical potential or the Gibbs Free energy behaves before a phase change, during the phase change and afterward.

Chapter 5

In previous chapters applications of the thermodynamics were applied to the case of pure substances. In Chapter 5, applications were extended to the thermodynamics of mixtures.

You should know that the total volume of a mixture is not necessarily the sum of the volumes of the pure substances since the volume occupied by the molecules is dependent upon the interactions of the molecules surrounding them. The partial molar volume describes this dependence and is the slope of the graph of the total volume as the amount of a component is changed. Once the partial molar volume is known at any composition, the total volume can be obtained. How?

Partial molar quantities can be extended to other state functions. One example is the partial molar Gibbs function, the chemical potential. Remember the Gibbs Duhem equation relates the changes in the chemical potentials of the components.

Systems tend toward a lower Gibbs Free energy. This allows us to apply thermodynamics to the discussion of spontaneous changes of composition. One specific application is the mixing of two gases. Look at

G of mixing to decide if the mixing will occur. You should be able to determine

S,

H,

V of mixing given

G of mixing.

What are the Excess functions?

When deriving the

G of mixing for binary solutions, we must decide if the solution is ideal, or ideal dilute, etc. You should know what the partial vapor pressure and total pressure vs liquid mole fraction or vapor mole fraction look like for Raoult’s

Law or Henry’s Law obeying mixtures. Why is there deviation from Raoults Law? Why do deviations occur both positively and negatively?

All colligative properties, freezing point depression, boiling point elevation, etc

stem from the reduction of the chemical potential of the liquid solvent as a result of the addition of a nonvolatile component being added. To derive the colligative constants, we simply set the chemical potentials of the solvent plus solute equal to the pure gas or solid chemical potential. Be familiar with freezing point depression, boiling point elevation, and osmotic pressure calculations. You should be familiar with the ebullioscopic and cryoscopic constants and the definitions of molality, mole fraction, and molarity. What is the Vant Hoff’s constant, i?

How can the activity of a solvent or solute be determined? How is the standard state for the activity different depending on whether we are talking about a solute or a solvent ideal; solution or ideal dilute solution. What is the relationship between the activity coefficients and the activity? The activity coefficients go to one in the limit of high solvent concentration or very low solute concentration. Again this is specific to the standard state applicable in a particular situation. What are the Margules factors. How do they relate to the Gibbs Free energy of mixing and the Excess Gibbs energy. How are they related to the activities and activity coefficients? Remember that for an ionic solution, the activity coefficients used are the mean activity coefficients. Replacing the activities with the molalities works only for dilute solutions. The mean activity coefficient can be derived from the Debye Huckel limiting law or the extended law with works at slightly higher ionic strengths, but remains poor near 1molal concentraiton.

Chapter 6

Background for this is the ability to use the Gibss phase rule and identify the various phase regions of a one component P vs T phase diagram.

You should be able to interpret pressure-composition, and temp. vs composition diagrams. You should be able to determine the composition of the vapor phase given information about the liquid phase composioin and the pure component vapor pressures for an ideal two component mixture. What does a plot of y

A

vs x a

look like? How about a P vs y

A

diagram or a P vs x

A

diagram from and ideal solution. In a two component phase diagram, we plot pressure as a function of z

A

(both y

A

and x

A

) or temp. as a function of z

A

(both y

A

and x

A

). Remember that pressure is being set for a temp. vs composition diagram and temp. is fixed for a pressure vs composition diagram. How do you know which component’s mole fraction is going from 0 to 1 from left to right on the x axis? Be able to describe the various regions on the phase diagrams, the number of phases, the number of degrees of freedom, and the various compositions present if an isopleth is followed. The lever rule can be used to determine the relative amounts

(moles) of the two phases present at a given overall concentration and temperature or pressure. Know how to show a simple distillation or fractional distillation on a temperature vs composition diagram. What is an azeotrope. How does it look on a temp vs composition diagram, and how does the way it looks correspond to a positive or negative deviation from Raoults law? Why are there both low boiling and high boiling azeotropes?

Be able to interpret liquid-liquid diagrams (temp-composition) for partially miscible liquids, liquid vapor temp vs composition diagrams for partially miscible liquids, and liquid-solid phase diagrams (temp-composition). Again, as before, you should know what phases are present in a particular region of the diagram as well as the # of degrees of freedom. Know how to label the axes and points on the axes. Know the

terms lower critical temperature, upper critical temperature, and eutectic point. Be able to identify incongruent melting and the presence of a product compound. Although there are three constituents there are only two components, why? What is the eutectic halt. Be able to construct a two component phase diagram from information about boiling point, melting points, eutectic points and general lines. Know how to use the triangular phase diagrams for three component systems, What is the difference in the diagram for miscible and partially miscible systems. Know what the constant two component molar ratio looks like on the diagram.

CHAPTER 7

Spontaneous change at constant temperature and pressure is in the direction of lower values of the Gibbs function. Why is a plot of G vs extent,

 a curve with a minimum rather than just a straight line. Know the definition of the extent of a reaction. How is it related to the coefficients in the balanced chemical eqn? What is the definition of the rxn

Gibbs function? Is it a partial molar function? What is the difference between the reaction Gibbs function and the standard reaction Gibbs free energy change, G o rxn

?

Remember for the reaction A

<-

- > B, the change per mole when 1 mol of A in its std state is converted to 1 mol of B in its std state is G o rxn

and these values come from the G o f

.

What do the terms endergonic and exergonic mean? Know the definition of the reaction

Gibbs function in terms of the reaction quotient Q. What is the value of

 r

G at equilibrium? How is the equilibrium constant related to G o rxn

? What is the relationship between the reaction quotient and the equilibrium constant?

You should be able to express the reaction quotient in most general terms as a function of the activities of the reactants and products, and more specifically in terms of pressures, fugacities, activity coefficients times molality, etc. The form of the expression depends on whether the system is an ideal gas or solution, or real gas or solution. What is the relationship between the various equilibrium constants such as K = K x

K p

or K = K

K m

Does the equilibrium constant change with pressure? Does the equilibrium constant change with temperature? Know the relations. What is the Van’t Hoff’s equation?. How does Le Chatelier’s principle fit with the effects of pressure and temperature on equilibrium?

You should be familiar with the Ellingham diagram and its use for determining whether or not the metal oxides can be converted to metal by adding carbon to them or at what temperature that this could occur.

Electrochemistry will not be covered on this exam.

Exam Specifics

Problems will be similar to homework problems. In Chp. 5 we focused on how thermodynamic parameters were a function of the composition. Calculations related to partial molar quantities or use of Henry’s Law or Raults law to determine the solubility or vapor pressure of a component or total pressure as a function of composition or a plot of pressure vs mole fraction for ideal and ideal dilute solutions. As you have seen many of

the problems from Chp 6 include relating x

A

and y

A,

interpretation of regions on various types of temperature vs. composition, or pressure vs. composition diagrams for a two component system exhibiting varying miscibility. You should be familiar with the determination of distillation parameters such as # of theoretical plates, eutectic compositions, incogruent melting, upper critical points, etc. Also, there may be a question on ternary diagrams, three component phase diagrams

Expect a problem or two calculating the equilibrium constant or the equilibrium composition for a particular reaction, and the temperature and pressure dependence of the equilibrium constant or the mole fraction part of the equilibrium constant

Look at quizzes for potential problems.

Electrochemistry

You should recognize the difference between a galvanic or voltaic cell and an electrolytic cell. What are the anode and the cathode. Be able to identify the type of half reactions that take place at the anode and cathode. You should be familiar with cell notation. How is DG = -nFE ? What about the equilibrium constant?

The Nernst Eqn. gives the cell potential at various concentrations.

the Nernst Eqn. How can one use the definition of the Standard Hydrogen Electrode to determine the cell potentials of other half reactions? These half reactions are in an electrolyte.

The thermodynamic properties of electrolyte solutions are discussed in terms of the chemical potentials and activities in much the same way as non-electrolyte solutions, but ions interact strongly with one another through their electric charges and deviations from ideality are important even at very low concentrations. Many ion reactions involve the transfer of electrons, and can be studied by allowing them to take place in an electrochemical cell. In this way we can tabulate thermodynamic information about solutions much like was done using Hess’s law and heats of formation or enthalpies of combustion in chapter 2.

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