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the transfer of energy as disorederly motion as the result of a temperature difference between the system and its surroundings.

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Heat

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the transfer of energy as orderly motion. is due to energy being expended against an opposing force; the product of the force and the distance moved against it

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Work

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the total amount of energy in a system regarless of how that energy is stored. sum of all kinetic and potential energy within the system

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internal energy, U

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when a system losses energy to the surroundings, U is negative. When the system gains energy from the surroundings, U is positive

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sign of internal enery

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the value of the property changes with the amount of the material that is present; ex. mass, internal energy

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extensive property

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independent of amount of material present; ex. temp or density

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intensive property

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the value of a particular property only depends on the state of the system at that time

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state functions

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volume, pressure, internal energy and entropy

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examples of state functions

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property that depends upon the path by which a system in one state is changed to another state

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path function

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heat and work

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ex. of path functions

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no account of how the state was prepared is necessary

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When performing calculations on state functions

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the total energy of an isolated thermodynamic system is constant; conservation of energy

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The first law of thermodynamics

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energy cannot be created or destroyed

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conservation of energy

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∆U = q + w

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first law equation

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energy is gained by the system as heat or work

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U, q, and w are positive if

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energy is lost b the energy as heat or work

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U, q, and w are negative if

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path; they do not depend on the initial and final states but on how the final state is reached

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heat and work are ___ functions

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w=-Pex∆V, U=-Pex∆V + q

answer

When there is pV/expansion work, w= _____, U= _____

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∆V=0, and ∆U=q

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if a reaction takes place in a sealed container at fixed volume then,

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robust metal container in which a reaction takes place. As the reaction exchanges heat with the surroundings, the temperature of the surroundings changes. ∆U=q. temperature rise is related to the heat output form the reaction; temperature of a system is proportional to the amount of heat input into it by the heat capacity, C=dq=CdT

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bomb calorimeter

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relates the amount of temperature of a system to the amount of heat which is input into the system

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heat capacity

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Cp= Cv + nR

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Cp and Cv are the same for solids and liquids, but For gases

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constant volume heat capacity

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Cv

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constant pressure heat capacity

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Cp

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dU = CvdT or ∆U =Cv∆T, when Cv is independent of temperature

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At constant volume, the heat supplied is equal to the change in internal energy, so it is possible to write

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molar heat capacity

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Cm

question

H= U + pV

answer

enthalpy equation

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constant pressure

answer

The enthalpy change for a process is equal to the heat exchange at

question

∆H=∆U+ p∆V (note: this is equal to Q)

answer

Enthalpy equation at constant pressure is

question

∆H=∆U+ ∆nRT, where ∆n is the molar change in gaseous component

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For a chemical system which releases or absorbs a gas a constant pressure, the enthalpy change is related to internal energy by

question

enthalpy increases

answer

endothermic

question

enthalpy decreases

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exothermic

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∆H=Cp∆T, provided that Cp does not appreciably change over the temperature range of interest. Otherwise, ∆H=∫CpdT.

answer

enthalpy change arising from a temperature change at constant pressure is

question

∆H=∆H(products) - ∆H(reactants)

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In a chemical reaction, the enthalpy change is equal to the difference between the reactants and products

question

∆H2 - ∆H1 =∫∆CpdT

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Where Cp does not appreciably change over the temperature range of interest, enthalpy may be expressed as

question

∆H=q

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When the only work done by the system is pV work, at constant pressure

question

the interanl energy change of that system and the work done by the system in expanding against the constant external pressure

answer

heat exchanged by a system at constant pressure is equal to the sum of the

question

true

answer

an increase in enthalpy leads to an increase in its temperature (true or false)

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exothermic process

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Loss of heat from a system lowers its temperature and is referred to as an

question

independent of the process from which they were formed

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Because enthalpy is a state function, the absolute enthalpy associated with the reactants and products in a reaction are

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the overall enthalpy change for a reaction is equal to the sum of the enthalpy changes for the individual steps in the reaction measured at the same temperature

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Hess's Law

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reverse the direction of the transfer through an infinitesimal change in the conditions

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if energy is transferred reversibly to or from a system, it must be possible to

question

dq(rev)/T

answer

for a reversible process at constant temperature, the change in entropy, dS, is given by

question

dS>dq/T

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For an irreversible process,

question

the entropy of a perfectly crystalline solid at the absolute zero of temperature is zero

answer

the third law of thermodynamics

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reversibly or irreversibly

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any process involving the transfer of energy from one body to another may take place

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energy is transferred in such a way that at any point in the process the transfer may be reversed by an infinitesimally small change in the conditions. The system is therefore in equilibrium throughout the transfer. This means that the energy must be transferred infinitely slowly.

answer

reversible process

question

energy is transferred in a manner which results in random motion and some of the energy is dissipated as heat. The process is irreversible because a proportion of this heat is dispersed irrecoverably, and the original conditions cannot be generated without work being done on the system.

answer

irreversible process

question

less

answer

in isothermal expansion of an ideal gas against an external pressure, the amount of work done in a reversible process is ____ than the amount of work done for an irreversible process

question

property and state function

answer

entropy is a thermodynamic ____ of a system and a ___ function

question

dS=dq(rev)/T (reversible process), dS/T(irreversible process)

answer

For any process in any system, under isothermal conditions, the change in entropy, dS, is defined as:

question

they are the same because entropy is a state function

answer

How does the system entropy change for a irreversible process relate to that of a reversible process

question

-dq/dT

answer

the entropy change of the surroundings is

question

zero

answer

the total entropy change for a reversible process is

question

greater than zero

answer

the total entropy change for an irreversible process is

question

dq(rev)=CdT and dS=CdT/T, ∆S=∫(C/T)dT

answer

If heat is added reversibly to a system, it is possible to measure the system entropy changes by measuring the heat capacity. Show the logic here.

question

q=∆H(phase change) and ∆S=∆H(phase change)/T

answer

For a phase change at constant pressure, what are q and ∆S?

question

∆S(vap) is approximately equal to 85 J/K mol for most materials. (Svap is noted for having a large absolute entropy of the gas phase)

answer

Trouton's Rule

question

zero

answer

the entropy of a perfectly crystalline solid at absolute temperature of zero is

question

has a measurable absolute value for any system

answer

because it is possible to measure entropy changes from a reference point using heat capacity measurements, entropy (unlike enthalpy and internal energy)

question

has a natural tendency to occur without the need for input of work into the system

answer

spontaneous process

question

expansion of a gas in a vacuum, ball rolling down a hill, flow of heat from a hot body to a cold one

answer

spontaneous process examples

question

energy in the form of work must be put into the system

answer

for a nonspontaneous process to occur

question

compression of a gas into a smaller volume, the raising of a weight against gravity, the flow of heat from a cold body to a hotter one

answer

examples of non-spontaneous processes

question

increases for an irreversible process and remains constant for a reversible process

answer

For entropy of an isolated system ___ for a irreversible process and ______ for a reversible process

question

decreases

answer

the entropy of an isolated system never

question

the standard entropies of the initial and final states of the system

answer

Because entropy is a state function, entropy changes in a system may be calculated from

question

quickly or randomly; it can take an infinite amount of time to occur

answer

Spontaneous does not mean that the reaction occurs

question

work

answer

a spontaneous process may be harnessed to do ____ on another system

question

does not have a natural tendency to occur

answer

non-spontaneous process

question

non-spontaneous

answer

in any system, the reverse of a spontaneous process must be

question

sum of the entropy change of the system and in the surroundings, and it must be greater than or equal to zero to comply with the second law

answer

the total entropy change is the

question

The total entropy change is greater than zero. For example, the reaction can be exothermic and the heat lost to the surroundings causes the ∆S of the surroundings to be positive and greater than the ∆S of the system.

answer

How can the entropy change of the system be less than 0, but the reaction still spontaneous.

question

G=H-TS

answer

Gibbs Free energy equation

question

∆G=∆H-T∆S

answer

at constant temperature and pressure, finite changes in free energy may be expressed as

question

volume

answer

The Helmholtz free energy, A, is applied at constant

question

A=U-TS

answer

The Helmholtz free energy equation

question

at constant temperature and pressure

answer

When are Gibbs free energy is equal to -T∆S

question

at constant temperature and volume

answer

Helmholtz free energy is equal to -T∆S

question

∆G<0 (constant pressure) and ∆A<0 (constant volume)

answer

For a spontaneous process what are Gibbs and Helmholtz free energy values?

question

state functions without measurable absolute values

answer

Gibbs and Helmholtz free energies are

question

the maximum amount of work, other than volume expansion work, which may be obtained from a process

answer

Define free energy change

question

spontaneous process

answer

∆G is negative for a

question

An exothermic reaction ∆H0

answer

What process is always spontaneous?

question

An exothermic reaction ∆H<0 with a negative entropy change ∆S<0

answer

What process is spontaneous only at low temperatures?

question

An endothermic reaction ∆H>0 with a positive entropy

answer

What process is spontaneous only at high temperatures?

question

T=∆H/∆S

answer

The temperature at which a reaction becomes spontaneous is

question

(d/dT(G/T))p = -H/T^2

answer

the Gibbs-Helmholtz equation relates the temperature dependence of gibbs free energy. It is expressed as

question

S(surroundings) = -∆H(system)/T

answer

∆S(surroundings) is related to the enthalpy change in the system at constant pressure through the relationship

question

∆S(total)= ∆S(surr) + ∆S(system) At constant pressure ∆S(total)= -∆H/T + ∆S(system) -T∆S(total)= ∆H(surr) -T∆S(system) ∆G= ∆H(surr)- T∆S(system)

answer

Derive Gibbs free energy equation from ∆S total

question

∆G=-T∆S(total)

answer

Gibbs free energy is the measure of the total entropy change for a process

question

spontaneous process at constant pressure

answer

Gibbs free energy is less than zero for a

question

spontaneous process at constant volume

answer

Helmholtz free energy is less than zero for a

question

∆G=∆G(standard) + RTln(Q), where Q is the reaction quotient

answer

Free energy varies markedly with composistion by the expression

question

∆S(total)= ∆S(surr) + ∆S(system)

answer

Derive Helmholtz free energy from total entropy

question

for closed system where changes occur under constant volume conditions, such as reactions or processes in solids

answer

When is helmholtz free energy useful

question

most process take place at constant pressure

answer

Why is the gibbs free energy more commonly used than helmholtz free energy

question

represents the maximum amount of work, other than pV work, which may be obtained from a process

answer

The most important property of the free energy is that it not only provides an indicaton of the spontaneity of a process but it also

question

some heat from the system must be lost to the surroundings to contribute to ∆S(surroundings) such that the total entropy is greater than zero

answer

In the case of a reaction for which ∆Ssystem is negative, what must happen for the reaction to be spontaneous

question

when the rate of the forward and backward reactions are equal

answer

When is equilibrium established

question

...

answer

at equilibrium, the gibbs free energy changes for both the forward and backward reactions are zero

question

∆G=∆G(standard) + RTln(K), where K is the equilibrium constant

answer

what is gibbs free energy in terms of the equilibrium constant

question

property that depends only on the number of solute molecules present

answer

colligative property

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