DAT Entropy and Enthalpy, DAT Thermodynamics

How to identify if dS of the rxn is positive or negative

-If there are more moles of gas on the reactant side, -dS -If there are more moles of gas on the product side, +dS

Entropy, enthalpy, and Gibbs free E are what kinds of fxns?

A state fxn that is independent of pathway; only depends on initial and final state of system

G to L to S represents what?

Decrease in entropy and enthalpy -exothermic process -dS and dH= - <0 -includes condensation, crystallization, and deposition.

equilibrium

Delta G = 0 (deltaS=deltaH/T).

non-spontaneous

Delta G > 0

spontaneous

DeltaG < 0

When can dS=0?

Only at absolute zero Kelvin with perfect crystals

How to measure T of rxn?

You cant so you measure T of surroundings -endothermic rxn- observed by cold/low T surroundings -Exothermic rxn- surroundings get hot

Enthalpy

dH= heat change at constant pressure -dH= + endothermic; system brings heat inside it and absorbs heat from surroundings; consumes heat form outside -dH= - exothermic

Gibb's free energy

deltaG = (Sum nDeltaGf, products)-(Sum nDeltaGf, reactants). deltaG=deltaGstandard+RTlnQ deltaGstandard=-RTlnKeq. deltaG=deltaH - TdeltaS DeltaG changes every time the condition changes. DeltaGstandard remains constant.

spontaneous at low temperatures

deltaG=deltaH - TdeltaS, where delta H is negative and delta S is negative.

spontaneous at all temperatures

deltaG=deltaH - TdeltaS, where delta H is negative and deltaS is positive

non-spontaneous at all temperatures

deltaG=deltaH - TdeltaS, where delta H is positive and delta S is negative.

spontaneous at high temperatures

deltaG=deltaH - TdeltaS, where delta H is positive and delta S is positive.

enthalpies of formation

deltaH = (Sum nDeltaHf, products)-(Sum nDeltaHf, reactants).

Gas to liquid

exothermic

Gas to solid

exothermic vapor deposition

Liquid to solid

exothermic; freezing is an exothermic process so the "beaker" gets hot -remove heat from the molecules -system loses heat

S to L to G represents what?

increase in entropy (more disordered molecules) and enthalpy -endothermic rxn - dS= + >0 - dH= + >0 - includes fusion, vaporization, and sublimation

entropy (S)

n= moles in balanced rxn dS=(Sum of nSproducts)-(Sum of nSreactants).

q and w are?

not state fxns