ACS Physical Chemistry Thermochemistry Study Guide

question

What is the third law of thermodynamics?
answer

The entropy of a perfect crystal is zero.
question

What is the second law of thermodynamics?
answer

As a whole, the universe always tends towards increasing entropy.
question

What is the relationship between number of microstates and entropy?
answer

More microstates = higher entropy
question

What is the relationship between temperature and entropy?
answer

Temperature increases, entropy increases (direct)
question

What is the relationship between atomic weight and entropy?
answer

Heavier = increased entropy (direct)
question

What happens to entropy when a substance is dissolved in another?
answer

Entropy increases
question

What is the relationship between moles of gas and entropy?
answer

When moles of gas increase, entropy increases (direct)
question

What is the relationship between free energy, enthalpy, and entropy?
answer

deltaG(system)=deltaH(system)-TdeltaS(system)
question

What does change in G measure?
answer

The extent of the spontaneity of a process, and the useful energy available from it
question

What is the relationship between work and spontaneous processes?
answer

Spontaneous processes produce work
question

What is the relationship between work and non-spontaneous processes?
answer

Non-spontaneous processes require work
question

What does -w mean?
answer

Work is being produced – spontaneous
question

What does a positive sign for w mean?
answer

Work is required – non-spontaneous
question

Can a change be spontaneous in both directions?
answer

No
question

What is an extensive property?
answer

Value depends on the amount of substance
question

What does ΔG > 0 mean?
answer

Non-spontaneous process – requires work
question

What does ΔG < 0 mean?
answer

Spontaneous process – produces work
question

What does standard free energy of formation mean? ΔGo
answer

The free energy change that occurs when 1 mole of a compound is made from its elements
question

What is the standard free energy of formation for an element in its standard state? ΔGf
answer

question

What does reversing a reaction do to the standard free energy of formation? ΔG0
answer

Changes its sign
question

Why are most exothermic reactions spontaneous?
answer

Because the large negative ΔH/large energy release makes the free energy change negative.
question

What happens when ΔH and ΔS have opposite signs?
answer

The reaction occurs spontaneously at all temperatures or at none.
question

What happens when enthalpy (ΔH) is negative and entropy (ΔS) is positive?
answer

Spontaneous at all temperatures, negative free energy
question

What is the likely sign of ΔH and ΔS for a combustion reaction?
answer

Negative ΔH, positive ΔS
question

What happens when ΔH is positive and ΔS is negative?
answer

Nonspontaneous at all temperatures
question

What happens when ΔH and ΔS are both positive?
answer

Reaction becomes spontaneous as temperature increases
question

What happens when ΔH and ΔS are both negative?
answer

Reaction becomes spontaneous as temperature decreases
question

Why can the maximum work of a system never obtained from a real process?
answer

Because such an irreversible process will always involve some free energy being converted to heat
question

How do you find where a reaction becomes spontaneous?
answer

Set ΔG equal to zero and solve — use T=deltaH/deltaS to find the temperature value.
question

Is a chemical reaction proceeding to equilibrium a spontaneous or non-spontaneous change?
answer

Spontaneous
question

How to determine reaction direction from ΔG?
answer

ΔG0 reaction proceeds to the left
question

Which direction does the reaction proceed if ΔG is positive?
answer

To the left / to reactants
question

Which direction does the reaction proceed if ΔG is negative?
answer

To the right/ to products
question

How to predict ΔS(system)? (change in entropy of a system)
answer

Positive ΔS(system) means available microstates increases/disorder increases
question

How to calculate the ΔSo (aka standard entropy change) of the formation of one mole of gas from its elements?
answer

1. Write the balanced chemical equation with the proper coefficients that make the product ONE MOLE. 2. Find the value of the one mole of product in Appendix B. This is the deltaS(standard) for the product. 3. Find the value of the reactants in Appendix B for deltaS(standard) and multiply them by the coefficients you got in step 1. 4. Use total = products-reactants for your final value.
question

How to calculate ΔG (free energy) using enthalpy ΔH and entropy ΔS values?
answer

ΔG=ΔH-TΔS
question

What is the equation that relates ΔG to K?
answer

ΔG=-RT ln K
question

What is the Boltzmann constant?
answer

ln(# of microstates)
question

What does a big W mean?
answer

More microstates
question

What does more microstates mean?
answer

Big ΔS – more entropy
question

What does fewer microstates mean?
answer

Smaller ΔS – less entropy
question

What happens to entropy when volume is increased?
answer

Microstates increase, entropy increases
question

What is the relationship between ΔS of a system, q, and T?
answer

ΔS(system)=qrev/T
question

What happens to entropy ΔS when temperature increases?
answer

It increases
question

What is the relationship between mass and entropy ΔS?
answer

As mass increases, entropy increases
question

What is the relationship between molecular complexity and entropy ΔS?
answer

As molecular complexity increases, entropy increases
question

What is the relationship between ΔG and Q?
answer

ΔG=RTlnQ
question

What happens to K as ΔG becomes more positive?
answer

It gets smaller
question

What happens to K as ΔG becomes more negative?
answer

It gets bigger
question

What direction does a reaction proceed if ln Q/K is positive?
answer

Reaction proceeds to the left/reactants
question

What direction does a reaction proceed if ln Q/K is negative?
answer

Reaction proceeds to the right/products
question

Extensive Property
answer

property which is directly proportional to the size of the system (i.e.. V, m, E )
question

Intensive Property
answer

property which does not depend on the size of the system (i.e. P, T, density, molar volume)
question

van der Waals constants
answer

a reflects how strong the molecules attract each other (IM forces); b reflects the size of the molecule — van der Waals equation extends beyond the ideal gas law to take into account attractive and repulsive forces
question

Isotherm
answer

plot of P as a function of molar volume at constant temperature
question

Law of Corresponding States
answer

Law which states “all gases have the same properties of they are compared at corresponding conditions”
question

Boyle Temperature
answer

temperature at which repulsive and attractive interactions cancel and the gas appears to behave ideally
question

Heat (q)
answer

the manner of energy transfer that results from temperature difference between system and surroundings (“unorganized motion”)
question

Work (w)
answer

the transfer of energy between system and surroundings as a result of existence of unbalanced forces between the two (“organized motion”)
question

State Function
answer

property that depends on the state of the system, and not upon the history of the system (i.e. energy, entropy)
question

Reversible Process
answer

when pressure the pressure exerted on the system and the pressure of the system differ only infinitesimally so slight changes are able to be made
question

Path Function
answer

property that depends on the path taken to reach the state of the system
question

Adiabatic Process
answer

process which no energy as heat is transferred (dq = 0 ; therefore, dU=dw )
question

Enthalpy (H)
answer

total heat content of a system; it is equivalent to the internal energy plus the products of pressure and volume
question

Heat of Combustion
answer

the heat involved in a combustion reaction –chemical reactions that absorb heat ( dH > 0) are called endothermic –chemical reactions that release heat (dH <0) are called exothermic
question

Entropy (S)
answer

unavailability of a system’s thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system —dS=0 for cyclic processes or reversible processes in isolated system —dS > 0 for spontaneous processes in isolated systems
question

Helmoltz Energy (A)
answer

= U – TS —will decrease during any spontaneous process that occur at constant T and V and will achieve its minimum value at equilibrium
question

Gibbs Energy (G)
answer

= H – TS = A + PV —will decrease as a result of any spontaneous process until the system reaches equilibrium
question

Fugacity
answer

thermodynamic property which described the deviations of ideality; the ratio f/p is the coefficient
question

Gibbs Phase Rule
answer

F = C – P + 2 —Phase (P): numer of phases ( P=1 is for within a region, P=2 is for on the coexistence curve, P=3 is for at the critical point) —Component (C): chemically independent variable describing how many components are in the system —Degrees of Freedom (F): number of intensive variables we can change yet still be in the same phase
question

Azeotrope
answer

a mixture for which there is no change in composition upon boiling (not possible to achieve separation)
question

Colligative Property
answer

property which depends only on the number of solute particles present, not on their identity (i.e. vapor pressure, boiling point, freezing point, osmotic pressure)
question

Reaction Quotient (Q) vs. Equilibrium Constant (K)
answer

— at equilibrium dG=0 ; Qp=Kp — If Qp < P: dG P: dG >0 so reaction is moving R to L
question

Colloids
answer

Contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension
question

Bose-Einstein Condensate
answer

Fifth state of matter that exists at extremely low temperatures and atoms behave as a single particle
question

Pressure
answer

Result of force distributed over an area
question

Charles’s Law
answer

The volume of a gas is directly proportional to its temperature in kelvins if the pressure and the # of particles of the gas are constant
question

Boyle’s Law
answer

The volume of a gas is inversely proportional to its pressure if the temperature and the # of particles are constant
question

Endothermic
answer

The system absorbs energy from its surroundings
question

Heat of Fushion
answer

The energy a substance must absorb in order to change from a solid to liquid
question

Exothermic
answer

The system releases energy to its surroundings
question

Deposition
answer

When a gas changes directly to a solid
question

Sublimation
answer

When a solid changes directly to a gas
question

Alkaline Earth Metals
answer

The elements in group 2A; differences shown by reactivity to water
question

Halogens
answer

The elements in group 7A; highly reactive nonmetals
question

Noble Gases
answer

The elements in group 8A; colorless odorless and extremely unreactive
question

Anion
answer

An ion with a negative charge
question

Cation
answer

An ion with a positive charge
question

Polar Covalent Bond
answer

A covalent bond in which electrons are not shared equally
question

2. An equation of state interrelates
answer

pressure, volume, temperature, and amount of substance: p = f(T,V,n).
question

6. A diathermic boundary is a boundary that
answer

permits the passage of energy as heat.
question

7. An adiabatic boundary is a boundary that
answer

prevents the passage of energy as heat.
question

7. Thermal equilibrium is a condition in which
answer

no change of state occurs when two objects A and B are in contact through a diathermic boundary.
question

8. The Zeroth Law of thermodynamics states that
answer

if A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then C is also in thermal equilibrium with A.
question

9. The Celsius and thermodynamic temperature scales are related by
answer

T/K = θ/°C + 273.15.
question

10. A perfect gas obeys the perfect gas equation
answer

pV = nRT, exactly under all conditions.
question

11. Dalton’s law states that the
answer

pressure exerted by a mixture of gases is the sum of the partial pressures of the gases.
question

12. The partial pressure of any gas is defined as
answer

p_J = x_J p, where x_J = n_J/n is its mole fraction in a mixture and p is the total pressure.
question

13. In real gases, molecular interactions affect the equation of state; the true equation of state is expressed in terms of virial coefficients
answer

B, C, . . . : pV_m = RT(1 + B/V_m + C/V^2_m + · · · ).
question

14. The vapour pressure is the
answer

pressure of a vapour in equilibrium with its condensed phase.
question

15. The critical point is the point at which the
answer

volumes at each end of the horizontal part of the isotherm have merged to a single point. The critical constants p_c, V_c, and T_c are the pressure, molar volume, and temperature, respectively, at the critical point.
question

16. A supercritical fluid is a
answer

dense fluid phase above its critical temperature and pressure.
question

17. The van der Waals equation of state is an
answer

approximation to the true equation of state in which attractions are represented by a parameter a and repulsions are represented by a parameter b: p = nRT/(V− nb) − a(n/V)^2.
question

18. A reduced variable is
answer

the actual variable divided by the corresponding critical constant.
question

19. According to the principle of corresponding states, real gases at the same reduced volume and reduced temperature exert
answer

the same reduced pressure.
question

2. The system is the part of the world in which we have a special interest. The surroundings is the region
answer

outside the system where we make our measurements.
question

3. An open system has a boundary through which matter can be
answer

transferred.
question

3. A closed system has a boundary through which matter
answer

cannot be transferred.
question

3. An isolated system has a boundary through which
answer

neither matter nor energy can be transferred.
question

4. Energy is the capacity to
answer

do work. The internal energy is the total energy of a system.
question

5. Work is the transfer of energy by motion against an opposing force,
answer

dw = −Fdz . Heat is the transfer of energy as a result of a temperature difference between the system and the surroundings.
question

6. An exothermic process
answer

releases energy as heat to the surroundings.
question

6. An endothermic process
answer

absorbs energy as heat from the surroundings.
question

7. A state function is a property that depends only on
answer

the current state of the system and is independent of how that state has been prepared.
question

8. The First Law of thermodynamics states that
answer

the internal energy of an isolated system is constant, ΔU = q + w.
question

9. Expansion work is the work of expansion (or compression) of a system,
answer

dw = −p_exdV. The work of free expansion is w = 0.
question

9. The work of expansion against a constant external pressure is
answer

w = −p_exΔV.
question

9. The work of isothermal reversible expansion of a perfect gas is
answer

w = −nRT ln(V_f /V_i).
question

10. A reversible change is a change that
answer

can be reversed by an infinitesimal modification of a variable.
question

11. Maximum work is achieved in a
answer

reversible change.
question

12. Calorimetry is the study of
answer

heat transfers during physical and chemical processes.
question

13. The heat capacity at constant volume is defined as
answer

C_V = (∂U/∂T) _V.
question

14. The heat capacity at constant pressure is
answer

C_p = (∂H/∂T) _p.
question

14. For a perfect gas, the heat capacities are related by
answer

C_p − C_V = nR.
question

14. The enthalpy is defined as
answer

H = U + pV.
question

14. The enthalpy change is the
answer

energy transferred as heat at constant pressure, ΔH = q_p.
question

15. During a reversible adiabatic change, the temperature of a perfect gas varies according to
answer

T_f = T_i(V_i/V_f)^(1/c), c = CV,m/R. The pressure and volume are related by pV^γ = constant, with γ = C_p,m/C_V,m.
question

16. The standard enthalpy change is the
answer

change in enthalpy for a process in which the initial and final substances are in their standard states. The standard state is the pure substance at 1 bar.
question

17. Enthalpy changes are additive, as in
answer

Δ_subH® = Δ_fusH® + Δ_vapH® .
question

18. The enthalpy change for a process and its reverse are related by
answer

ΔforwardH® = −ΔreverseH®.
question

19. The standard enthalpy of combustion is the
answer

standard reaction enthalpy for the complete oxidation of an organic compound to CO2 gas and liquid H2O if the compound contains C, H, and O, and to N2 gas if N is also present.
question

20. Hess’s law states that the standard enthalpy of an overall reaction is the
answer

sum of the standard enthalpies of the individual reactions into which a reaction may be divided.
question

21. The standard enthalpy of formation (Δ_fH® ) is the
answer

standard reaction enthalpy for the formation of the compound from its elements in their reference states. The reference state is the most stable state of an element at the specified temperature and 1 bar.
question

22. The standard reaction enthalpy may be estimated by combining enthalpies of formation
answer

Δ_rH® =ΣProducts νΔfH® −ΣReactants νΔfH® .
question

23. The temperature dependence of the reaction enthalpy is given by Kirchhoff’s law
answer

Δ_rH® (T2) = Δ_rH® (T1) + Integral (T2 to T1) Δ_rC® pdT.
question

24. An exact differential is an
answer

infinitesimal quantity that, when integrated, gives a result that is independent of the path between the initial and final states. An inexact differential is an infinitesimal quantity that, when integrated, gives a result that depends on the path between the initial and final states.
question

25. The internal pressure is defined as
answer

π_T = (∂U/∂V) _T . For a perfect gas, π_T = 0.
question

26. The Joule-Thomson effect is the
answer

cooling of a gas by isenthalpic expansion.
question

27. The Joule-Thomson coefficient is defined as
answer

μ = (∂T/∂p) _H.
question

27. The isothermal Joule-Thomson coefficient is defined as
answer

μ_T = (∂H/∂p) _T = −C_pμ.
question

28. The inversion temperature is the
answer

temperature at which the Joule-Thomson coefficient changes sign.
question

2. The Second Law in terms of entropy:
answer

The entropy of an isolated system increases in the course of a spontaneous change: ΔS_tot > 0.
question

3. The thermodynamic definition of entropy is
answer

dS = dq_rev /T.
question

4. The statistical definition of entropy is given by the Boltzmann formula
answer

S = k lnW.
question

4. A Carnot cycle is a cycle composed of a
answer

sequence of isothermal and adiabatic reversible expansions and compressions.
question

5. The efficiency of a heat engine is
answer

ε = |w|/q_h.
question

5. The Carnot efficiency is
answer

ε_rev = 1 − T_c /T_h.
question

7. The Clausius inequality is
answer

dS ≥ dq/T.
question

8. The normal transition temperature, T_trs, is the temperature at which
answer

two phases are in equilibrium at 1 atm.
question

8. The entropy of transition at the transition temperature is
answer

Δ_trsS = Δ_trsH/T_trs.
question

9. Trouton’s rule states that
answer

many normal liquids have approximately the same standard entropy of vaporization (about 85 J K−1 mol−1).
question

10. The variation of entropy with temperature is given by
answer

S(T_f) = S(T_i) + Integral (T_f to T_i) (C_p /T)dT.
question

11. The entropy of a substance is measured from the
answer

area under a graph of C_p /T against T, using the Debye extrapolation at low temperatures, C_p = aT3 as T→0.
question

12. The Nernst heat theorem states that the entropy change accompanying any physical or chemical transformation
answer

approaches zero as the temperature approaches zero: ΔS→0 as T→0 provided all the substances involved are perfectly ordered.
question

13. Third Law of thermodynamics:
answer

The entropy of all perfect crystalline substances is zero at T = 0.
question

14. The standard reaction entropy is calculated from
answer

Δ_rS® =ΣProducts νS® m -Σreactants νS® m .
question

15. The standard molar entropies of ions in solution are reported on a scale in which
answer

S* (H+, aq) = 0 at all temperatures.
question

16. The Helmholtz energy is
answer

A = U − TS.
question

16. The Gibbs energy is
answer

G = H − TS.
question

17. The criteria of spontaneity may be written as:
answer

(a) dS_U,V ≥ 0 and dU_S,V ≤ 0, or (b) dA_T,V ≤ 0 and dG_T,p ≤ 0.
question

18. The criterion of equilibrium at constant temperature and volume,
answer

dA_T,V = 0.
question

18. The criterion of equilibrium at constant temperature and pressure,
answer

dG_T,p = 0.
question

19. The maximum work and the Helmholtz energy are related by
answer

w_max = ΔA.
question

19. The maximum additional (non-expansion) work and the Gibbs energy are related by
answer

w_add,max = ΔG.
question

20. The standard Gibbs energy of reaction is given by
answer

Δ_rG® = Δ_rH® − TΔ_rS® =ΣProducts νG® m -Σreactants νG® m .
question

21. The standard Gibbs energy of formation (Δ_fG®) is the
answer

standard reaction Gibbs energy for the formation of a compound from its elements in their reference states.
question

22. The standard Gibbs energy of reaction may be expressed in terms of
answer

Δ_fG®, Δ_rG® =ΣProducts νΔfG® −ΣReactants νΔfG®.
question

23. The standard Gibbs energies of formation of ions are reported on a scale in which
answer

Δ_fG® (H+, aq) = 0 at all temperatures.
question

24. The fundamental equation is
answer

dU = TdS − pdV.
question

25. The Maxwell relations are
answer

.
question

26. A thermodynamic equation of state is an
answer

expression for pressure in terms of thermodynamic quantities, π_T = T(∂p/∂T) _V − p.
question

27. The Gibbs energy is best described as a function of pressure and temperature,
answer

dG = Vdp − SdT.
question

27. The variation of Gibbs energy with pressure and temperature are, respectively,
answer

(∂G/∂p) _T = V and (∂G/∂T) _p = −S.
question

28. The temperature dependence of the Gibbs energy is given by the Gibbs-Helmholtz equation,
answer

(∂(G/T)/∂T) _p = −H/T2.
question

29. For a condensed phase, the Gibbs energy varies with pressure as
answer

G(p_f) = G(p_i) + V_mΔp. For a perfect gas, G(p_f) = G(p_i) + nRT ln(p_f/p_i).
question

1. A phase is a form of matter that is
answer

uniform throughout in chemical composition and physical state.
question

2. A transition temperature is the temperature at which the two phases are in
answer

equilibrium.
question

3. A metastable phase is a
answer

thermodynamically unstable phase that persists because the transition is kinetically hindered.
question

4. A phase diagram is a diagram showing the
answer

regions of pressure and temperature at which its various phases are thermodynamically stable.
question

5. A phase boundary is a
answer

line separating the regions in a phase diagram showing the values of p and T at which two phases coexist in equilibrium.
question

6. The vapour pressure is the
answer

pressure of a vapour in equilibrium with the condensed phase.
question

7. Boiling is the condition of
answer

free vaporization throughout the liquid.
question

8. The boiling temperature is the temperature at which the
answer

vapour pressure of a liquid is equal to the external pressure.
question

9. The critical temperature is the temperature at which a liquid surface
answer

disappears and above which a liquid does not exist whatever the pressure. The critical pressure is the vapour pressure at the critical temperature.
question

10. A supercritical fluid is a
answer

dense fluid phase above the critical temperature.
question

11. The melting temperature (or freezing temperature) is the temperature at which, under a specified pressure, the liquid and solid phases of a substance
answer

coexist in equilibrium.
question

12. The triple point is a point on a phase diagram at which
answer

the three phase boundaries meet and all three phases are in mutual equilibrium.
question

13. The chemical potential μ of a pure substance is the
answer

molar Gibbs energy of the substance.
question

14. The chemical potential is
answer

uniform throughout a system at equilibrium.
question

15. The chemical potential varies with temperature as
answer

(∂μ /∂T) _p = −S_m and with pressure as (∂μ /∂p) _T = V_m.
question

16. The vapour pressure in the presence of applied pressure is given by
answer

p = p*e^(V_mΔP/RT).
question

17. The temperature dependence of the vapour pressure is given by the Clapeyron equation,
answer

dp/dT = Δ_trsS/Δ_trsV.
question

18. The temperature dependence of the vapour pressure of a condensed phase is given by the Clausius-Clapeyron equation,
answer

d ln(p/dT) = Δ_vapH/RT^2.
question

19. The Ehrenfest classification is a classification of
answer

phase transitions based on the behavior of the chemical potential.
question

1. The partial molar volume is the
answer

change in volume per mole of A added to a large volume of the mixture: V_J = (∂V/∂n_J)_p,T,n′.
question

1. The total volume of a mixture is
answer

V = n_AV_A + n_BV_B.
question

2. The chemical potential can be defined in terms of the partial molar Gibbs energy,
answer

μ_ J = (∂G/∂n_J) _p,T,n′.
question

2. The total Gibbs energy of a mixture is
answer

G = n_Aμ_A + n_Bμ_B.
question

3. The fundamental equation of chemical thermodynamics relates the change in Gibbs energy to changes in pressure, temperature, and composition:
answer

dG = Vdp − SdT + μ_Adn_A + μ_Bdn_B + · · ·.
question

4. The Gibbs-Duhem equation is
answer

Σn_Jdμ_J = 0.
question

5. The chemical potential of a perfect gas is
answer

μ = μ*+ RT ln(p/p*), where μ* is the standard chemical potential, the chemical potential of the pure gas at 1 bar.
question

6. The Gibbs energy of mixing of two perfect gases is given by
answer

Δ_mixG = nRT(x_A ln x_A + x_B ln x_B).
question

7. The entropy of mixing of two perfect gases is given by
answer

Δ_mixS = -nR(x_A ln x_A + x_B ln x_B).
question

8. The enthalpy of mixing for perfect gases is
answer

Δ_mixH = 0 for perfect gases.
question

9. An ideal solution is a solution in which all components obeys Raoult’s law
answer

(p_A = x_Ap_A*) throughout the composition range.
question

10. The chemical potential of a component of an ideal solution is given by
answer

μ_A = μ_A* + RT ln x_A.
question

11. An ideal-dilute solution is a solution for which the solute obeys Henry’s law
answer

(p_B = x_BK_B*) and the solvent obeys Raoult’s law.
question

12. The Gibbs energy of mixing of two liquids that form an ideal solution is given by
answer

Δ_mixG = nRT(x_A ln x_A + xB ln xB).
question

13. The entropy of mixing of two liquids that form an ideal solution is given by
answer

Δ_mixS = -nR(xA ln xA + xB ln xB).
question

14. An excess function (XE) is the
answer

difference between the observed thermodynamic function of mixing and the function for an ideal solution.
question

16. A colligative property is a property that
answer

depends only on the number of solute particles present, not their identity.
question

17. The elevation of boiling point is given by
answer

ΔT = K_bb, where Kb is the ebullioscopic constant.
question

17. The depression of freezing point is given by
answer

ΔT = K_fb, where Kf is the cryoscopic constant.
question

21. The activity is defined as
answer

a_A = p_A/p_A*.
question

22. The solvent activity is related to its chemical potential by
answer

μ_A = μ_A* + RT ln a_A. The activity may be written in terms of the activity coefficient γ_A = a_A/x_A.
question

26. The Debye-Hückel theory of activity coefficients of electrolyte solutions is based on the assumption that
answer

Coulombic interactions between ions are dominant; a key idea of the theory is that of an ionic atmosphere.
question

5. Thermal analysis is a technique for
answer

detecting phase transitions that takes advantage of the effect of the enthalpy change during a first-order transition.
question

6. The vapour pressure of an ideal solution is given by
answer

p = p*_B + (p*_A − p*_B)x_A.
question

6. The composition of the vapour of an ideal solution,
answer

y_A = x_Ap*_A/{p*_B + (p*_A − p*_B)x_A}, y_B = 1 − yA.
question

7. The total vapour pressure of a mixture is given by
answer

p = p_A * p*_B/{p*_A + (p*_B − p*_A)y_A}.
question

8. An isopleth is a line of
answer

constant composition in a phase diagram. A tie line is a line joining two points representing phases in equilibrium.
question

9. The lever rule allows for the calculation of the relative amounts of two phases in equilibrium:
answer

nαlα = nβlβ.
question

10. A temperature-composition diagram is a phase diagram in which the boundaries show the
answer

composition of the phases that are in equilibrium at various temperatures.
question

11. An azeotrope is a mixture that
answer

boils without change of composition.
question

12. Partially miscible liquids are liquids that
answer

do not mix in all proportions at all temperatures.
question

13. The upper critical solution temperature is the
answer

highest temperature at which phase separation occurs in a binary liquid mixture.
question

13. The lower critical solution temperature is the
answer

temperature below which the components of a binary mixture mix in all proportions and above which they form two phases.
question

14. A eutectic is the mixture with the
answer

lowest melting point; a liquid with the eutectic composition freezes at a single temperature. A eutectic halt is a delay in cooling while the eutectic freezes.
question

15. Incongruent melting occurs when a compound
answer

melts into its components and does not itself form a liquid phase.
question

1. The extent of reaction (ξ) is defined such that,
answer

when the extent of reaction changes by a finite amount Δξ, the amount of A present changes from n_A,0 to n_A,0− Δξ.
question

2. The reaction Gibbs energy is the slope of the graph of the Gibbs energy plotted against the extent of reaction:
answer

Δ_rG = (∂G/∂ξ) _p,T; at equilibrium, Δ_rG = 0.
question

3. An exergonic reaction is a reaction for which
answer

Δ_rG 0.
question

4. The general expression for ΔrG at an arbitrary stage of the reaction is
answer

Δ_rG = Δ_rG* + RT ln Q.
question

5. The equilibrium constant (K) may be written in terms of Δ_rG* as
answer

Δ_rG* = −RT ln K.
question

6. The standard reaction Gibbs energy may be calculated from standard Gibbs energies of formation,
answer

ΔrG*=ΣProducts νΔfG* −ΣReactants νΔfG*=Σν_JΔ_fG* (J).
question

7. Thermodynamic equilibrium constant is an equilibrium constant K expressed in terms of activities (or fugacities):
answer

K = Πa_J ν_J Equilibrium .
question

8. A catalyst does not affect the
answer

equilibrium constant.
question

9. Changes in pressure do not affect the equilibrium constant:
answer

(∂K/∂p) _T = 0. However, partial pressures and concentrations can change in response to a change in pressure.
question

10. Le Chatelier’s principle states that a system at equilibrium, when subjected to a disturbance,
answer

responds in a way that tends to minimize the effect of the disturbance.
question

11. Increased temperature favors the ____ in exothermic reactions and the _____ in endothermic reactions.
answer

Reactants and Products.
question

12. The temperature dependence of the equilibrium constant is given by the van ‘t Hoff equation:
answer

d(ln K/dT) = Δ_rH*/RT^2. To calculate K at one temperature in terms of its value at another temperature, and provided ΔrH* is independent of temperature, we use ln K2 − ln K1 = −(Δ_rH*/R)(1/T_2 − 1/T_1).
question

13. A galvanic cell is an electrochemical cell that
answer

produces electricity as a result of the spontaneous reaction occurring inside it.
question

13. An electrolytic cell is an electrochemical cell in which a
answer

non-spontaneous reaction is driven by an external source of current.
question

14. Oxidation is the
answer

removal of electrons from a species.
question

14. Reduction is the
answer

addition of electrons to a species
question

14. A redox reaction is a reaction in which there is a transfer of
answer

electrons from one species to another.
question

15. The anode is the electrode at which
answer

oxidation occurs.
question

15. The cathode is the electrode at which
answer

reduction occurs.
question

16. The electromotive force (emf) is the cell potential when
answer

it is balanced by an exactly opposing source of potential so that the cell reaction occurs reversibly, the composition is constant, and no current flows.
question

17. The cell potential and the reaction Gibbs energy are related by
answer

−νFE = Δ_rG.
question

18. The standard emf is the standard reaction Gibbs energy expressed as a potential:
answer

E® = Δ_rG® /νF.
question

19. The Nernst equation is the equation for the emf of a cell in terms of the composition:
answer

E = E® − (RT/νF) ln Q.
question

20. The equilibrium constant for a cell reaction is related to the standard emf by
answer

ln K = νFE® /RT.
question

21. The standard potential of a couple (E®) is the standard emf of a cell in which a couple forms the ______ and the standard hydrogen electrode is the _____.
answer

Right-hand electrode and Left-hand electrode.
question

22. To calculate the standard emf, form the difference of electrode potentials:
answer

E® = E® (right) − E® (left).
question

23. The temperature coefficient of cell potential is given by
answer

dE® /dT = Δ_rS® /νF.
question

24. The standard reaction entropy and enthalpy are calculated from the temperature dependence of the standard emf by:
answer

Δ_rS ® = νFdE® /dT, Δ_rH® = −ν(FE ® − TdE® /dT).
question

Calorimetry
answer

Method of determining heat change in a system by measuring heat exchanged in the surroundings
question

What enthalpy sign do exothermic reactions have?
answer

Negative
question

What enthalpy sign do endothermic reactions have?
answer

Positive
question

Le Châtelier’s Principle
answer

States that if an equilibrium system is subject to change, the equilibrium shifts in the direction which tends to counter that change
question

Isobaric
answer

Constant P
question

Isothermal
answer

Constant T
question

Isochoric
answer

Constant V
question

Adiabadic
answer

No heat flows in or out of the system (Q =0; ∆U = W)
question

Relationship between heat and work
answer

∆U = Q + W
question

Work Equation
answer

W = -Pext (Vf – Vi)
question

Enthalpy
answer

H = U + PV
question

Change in enthalpy at constant presssure
answer

∆H = ∆U + P∆V
question

Equation for Cv for monoatomic gas
answer

Cv = (3/2)R
question

Equation for Cp for monoatomic gas
answer

Cp = (5/2)R
question

Equation for Cv for diatomic gas
answer

Cv = (5/2)R
question

Equation for Cp for diatomic gas
answer

Cp = (7/2)R
question

Gibb’s phase rule
answer

f = c – p + 2 (f is the number of degrees of freedom of a system; c is the number of components is the system; p is the number of phases present)
question

Boyle’s Law
answer

At constant T and for a given sample of gas, the pressure of a gas is inversely proportional to its volume
question

Boyle’s Law
answer

, P∝1/V
question

Charles’ Law
answer

The volume of a given sample of gas at constant pressure is proportional to its absolute temperature
question

V∝T
answer

Charles’ Law
question

The Kinetic Model of Gases is based on what assumptions?
answer

1) Gas consists of molecules in ceaseless random motion moving in straight linesbetween collisions , 2) The size of the molecule is negligible , 3) The molecules do not interact with each other or the wall of the vessel
question

Root-mean-square (r.m.s) speed
answer

c=√(3RT/M), Molar mass must be in kg mol-1, Temperature must be in K, Units = ms-1
question

What is the van der Waals equation of state?
answer

(p+a(n/v)^2)(V-nb) = RT , a and b are van der Waals parameters, specific for a given gas but independent of temperature
question

What is the equation for the molar heat capacity and give its units?
answer

q = Cm x n x ∆T , Units: J K-1 mol-1
question

What is the equation for the specific heat capacity and give its units?
answer

, q = Cs x m x ∆T , Units: J K-1 g-1 , The specific heat capacity of liquid water is 4.18 JK-1 g-1 Calculate the energy required to heat 1 mol of water from 25 °C to 90 °C , q = Cs x n x ∆T = 4.18 x 18 x (90-25) = 4.9kJmol-1
question

When a gas expands and moves a piston, how do you calculate the work done ?
answer

Work done = external pressure x change in volume, The system is losing energy the external pressure is negative
question

work done = -p(ex) x ∆V , Calculate the work done when a gas is compressed from 750cm3 to 500cm3 by an external pressure of 100kPa , work done = external pressure x change in volume , = 100×10^3 (Pa) x 250×10^-6 (m3) = 25J , Because the gas is compressed the external pressure is positive
answer

question

What type of property is internal energy?
answer

Both extensive and a state function
question

What is internal energy, give its symbol and give the equation for a change in internal energy
answer

Internal energy is the total energy of a system, It has the symbol U, ∆U = q + w
question

What is the relationship between enthalpy change and internal energy?
answer

∆U = ∆H -p∆V p is pressure (constant)
question

What is the equation for the variation of entropy with temperature?
answer

∆S = q(rev) / T , q(rev) = quantity of heat added reversibly ∆S = Cp ln (Tf/Ti)
question

What is the difference between K and Q?
answer

K is the thermodynamic equilibrium constant and is calculated at equilibrium whereas Q although calculated in the same way it doesn’t have to be at equilibrium
question

What relationship between Q and K has a tendency to form products?
answer

Q < K
question

What relationship between Q and K has a tendency to form reactants?
answer

Q > K
question

What is the relationship between ∆rG and K?
answer

∆rG = -RT lnK
question

What is the van’t Hoff equation for a reaction at a given temperature
answer

lnK = (∆rS/R) – (∆rH/RT)
question

The equilibrium for the dissociation of one mole of iodine vapour is 3.94 x10-4 at 900K and the standard enthalpy is 154 kJmol-. Calculate the equilibrium constant at 1200K assuming the standard enthalpy remains constant
answer

ln(K2/K1) = – ∆rH/R(1/T2 – 1/T1) , ANS = 6.7 x 10-2 at 1200K
question

At low vapour pressure, it is easy for a liquid to transition into a gas, true or false?
answer

True
question

What is a Daniell cell’s cell diagram?
answer

Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)
question

What is a Galvanic Cell?
answer

An electrochemical cell that produces electricity as a result of a spontaneous reaction
question

What is an Electrolytic Cell?
answer

A non-spontaneous reaction is forced by an external source of current
question

What is a Fuel Cell?
answer

Galvanic cells in which the reagents are supplied continuously
question

During cell notation where is the oxidation half reaction?
answer

Left
question

During cell notation where is the reduction half reaction?
answer

Right
question

What side does the anode appear in the cell notation?
answer

Left
question

What side does the cathode appear in the cell notation?
answer

Right
question

What is the cell notation for a calomel electrode?
answer

Hg(l) | Hg2Cl2(s) | Cl-(aq)
question

Standard electrode potentials are given as? (oxidation/reduction)
answer

reduction
question

What is the relationship between electrical work and standard gibbs energy change for a reaction?
answer

∆rG = we = -VQ, 1J = 1V x 1C
question

If Ecell is positive what will ∆rG be?
answer

∆rG will be negative therefore the reaction is spontaneous
question

What is the energy per photon and what is its units?
answer

E = hv = hc/ λ , Units: Joules
question

What is the equation for transmittance?
answer

T = It/I0 , light intensity emmitted / light intensity added
question

What is the equation for absorbance?
answer

A = – log T
question

If a sample absorbs 20% of light what is T and A?
answer

T = 0.8 , A= – log (0.8) = 0.1
question

What is Beer-Lambert Law? Give units
answer

A = εcl , A has no units so the units must cancel out , ε usually in dm3 mol-1 cm-1 , c has to be in mol dm-3 , l has to be in cm
question

Repulsive
answer

Force exist between the molecules of gasses when Z>1
question

Clapeyron equation
answer

Governs the temperature dependence of pressure in a two-phase, one component system
question

Clausius-Clapeyron equation
answer

Gives the relationship between pressure and temperature for a two phase, one component system assuming that the vapor phase is ideal and the molar volume of the condensed phase is negligible compared to vapor phase

Get instant access to
all materials

Become a Member