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60 Cards in this Set

  • Front
  • Back

The First Law of Thermodynamics is also known as the...

Law of Conservation of Energy.

In an process that involves an energy transaction,...

a "heat tax" must be paid.

Thermodynamics allows predictions of which processes...

will occur spontaneously.

A spontaneous process occurs without...

ongoing outside intervention.

For mechanical systems, the direction of spontaneity is...

towards lower potential energy.

For chemical systems, we need...

analagous concept.

Note that spontaneous process is not equivalent to...

a fast process. Thermodynamics and kinetics study different aspects of a chemical reaction.

Non-spontaneous processes...

can and do occur with outside assistance.

Examination of spontaneous endothermic processes leads to...

the importance of increasing disorder in chemical processes.

Disorder or randomness is...

the qualitative description of entropy.

entropy(S): a thermodynamic function that...

increases with the number of energetically equivalent ways to arrange the components a system to achieve a particular state.

The most common units for entropy are


Entropy is a...

state function, facilitating calculations of changes in entropy.

Entropy determines...

the direction of physical and chemical change.

A macrostate is...

what the system looks like from the outside; a micro-state is what the system looks like from the inside.

It is quite possible and common to have many different...

micro-states that represent the same macrostate.

Systems tend towards the most...

probable state which coincides with the state with greatest entropy.

The state with the highest...

entropy is the one that disperses energy the most.

States with low energy concentration have...

higher entropy than states with high energy concentration (as long as the amount of energy is constant between states).

The Second Law of Thermodynamics states...

that for any spontaneous process, the entropy of the universe increases.

As a substance goes from solid to gas, its entropy...

increases due to the number of ways it can "hold" energy.

Reactions resulting in an increase in the number of moles of gas...

increase entropy.

Since the 2nd Law of Thermodynamics require that the entropy of the universes increases, it is...

possible for the entropy of a system to decrease as long as the entropy of the surroundings increases enough to offset it.

If a system releases energy to the surroundings, the entropy...

of the surroundings increases.

Entropy is temperature dependent. For a constant amount of energy dispersed,...

DeltaS decreases as temperature increases.

Gibbs Free Energy, (G), is formally defined as...

G= H - TS

DeltaG can be used...

to determine spontaneity using only information about the system.

If DeltaG is negative, the process is...

spontaneous, if deltaG is positive, the process is non-spontaneous.

Since DeltaG involves DeltaH, DeltaS and T, different combinations of...

enthalpy entropy and temperature determine the sign on DeltaG and hence the spontaneity.

The standard entropy change for a reaction, DeltaS^o of reaction, is..

the change in entropy for a process in which all reactants and products are in their standard states.

The Third Law of Thermodynamics states...

that the entropy of a perfect crystal at absolute zero (0 K) is zero

The Third Law of Thermodynamics provides a reference point for...

all other entropies.

Entropy increases as...

substance goes from solid to liquid to gas.

The greater the molar mass,...

the higher the entropy.

Less constrained allotropes have...

more entropy than more constrained ones.

Complex compounds have...

more entropy than simpler compounds.

Dissolved ionic solids have...

more entropy than the undissolved solid.

Changes in standard entropies can...

be calculated via a Hess's Law type of calculation.

DeltaG^o of reaction can be calculated by...

separately calculating, the standard enthalpy change and the standard entropy change and using those values in the Gibbs free energy equation.

Just like a standard enthalpy of formation, there is a...

standard free energy of formation (DeltaG^o of f). The standard free energy of formation is the change in free energy when 1 more of a compound forms from its constituent elements in their standard states.

Reactions with associated free energies can be...

manipulated like thermochemical equations:

1. If an equation is multiplied by a factor, then the associated free energy change is multiplied by the same factor.

2. If an equation is reversed, then the free energy change switches sign;

3. If a series of reactions adds up to an overall reaction, the free energy change for the overall reaction is simply the sum of the free energy changes for each step.

Free energy is called "free" because...

it is the energy that is theoretically available to do work.

The only way to get the theoretical maximum work from a chemical system is to...

have the system change infinitesimally slowly such that the reaction is reversible.

Free energies can also be calculated....

under nonstandard conditions.

If there is no change in free energy, i.e. DeltaG = 0, then...

the system is at equilibrium.

Equilibrium constants and changes in free energy are...

intimately related.

Equilibrium constants are...

temperature dependent. Data of K's obtained at different temperature can be used to find the standard enthalpy, standard entropy, and standard free energy changes for a system.

S = k ln W

(Entrop equation)

DeltaS = S_final - S_initial

(Change in entropy equation)

DeltaS_Universe > 0

(2nd law of Thermodynamics)

DeltaS_Universe = DeltaS_system + DeltaS_surroundings

(Components of entropy of the universe)

DeltaS_Surroundings = (-DeltaH_System/T)

(Equation to calculate entropy change of surroundings)

DeltaG = DeltaH_system - T DeltaS_system

(Gibbs free energy equation)

G = H - TS

(Definition of Gibbs free energy)

DeltaS^o_reaction = S^o_products - S^o_reactants

(Standard entropy change for a reaction)

DeltaS^o_reaction = Sum of all moles_product * S^o(products) - Sum of all moles reactants * S^o (reactants)

(Calculation of DeltaS^o_reaction)

DeltaG^o_reaction = Sum of all moles_product * G^o_f(products) - Sum of all moles reactants * G^o_f (reactants)

(Hess's Law type calculation for DeltaG^o_reaction)

DeltaG_reaction =G^o_reaction + RT lnQ

(Calculating nonstandard free energy)

DeltaG^o_reaction = -RT ln K

(Relationship between DeltaG^o_reaction and K)

ln K = (-DeltaH^o_reaction/R) (1/T) + (DeltaS^o_reaction/R)

(Relation between equilibrium constant and temperature)