Chapter 10 Spotaneity

How does entropy change increase, ΔS , as states of matter change

solid<liquid « gas

Entropy symbol

ΔS

what does Entropy measure?

randomness

how does volume of effect ΔS for gas?

increases randomness

how does number of moles of gas effect entropy?

an increase in moles of gas means an increase in ΔS

if ΔS universe > 0

the reaction is product favored

Third Law of Thermodynamics

the entropy of pure crystal at 0K is zero

A reaction in spontaneous if…

ΔS universe > 0

A reaction is nonspontaneous if…

ΔS universe < 0

A reaction is in equilibrium if…

ΔS universe = 0

A reaction proceeds in the forward direction spontaneously if

ΔG = ΔH - TΔS < 0

criteria for a spontaneous process…

ΔG < 0

criteria for nonspontaneous process…

ΔG > 0

criteria for in equilibrium

ΔG = 0

Gibbs Free Energy

G = H - TS

A reaction is spontaneous @ HIGH T

ΔH > 0 ΔS > 0

A reaction is spontaneous @ LOW T

ΔH < 0 ΔS < 0

A reaction is ALWAYS spontaneous

ΔH < 0 ΔS > 0

A reaction is ALWAYS NONSPONTANEOUS

ΔH > 0 ΔS < 0

Standard molar Entropies S°

intensive state function (J/ mol x K)

Equation for Standard Molar Entropy

ΔS°reaction​=∑nS°products​−∑nS°reactants​

Equation for entropy of the universe

=ΔSsys - ΔHsys/T

Entropy as a function of temperature

as T increases, S increases

the equation ΔSsys = qsys/ T is only applicable if

the reaction is reversible

as heat enters the system

S of surroundings increases

as heat leaves the system

S of surroundings increases

How does pressure effect entropy

as S increases, P(atm) decreases @ constant T

Molar entropy of solute [x]…

increases with decreasing molarity of [x]

for a reaction under NONSTANDARD conditions, ΔS satisfies

ΔS​=∑nSproducts​−∑nSreactants​