LO 66 - 74 Flashcards
What is nature’s heat tax?
on every energy transaction, some energy is lost/dissipated as heat to the surroundings
______ processes occur without outside intervention such as work by an external force
spontaneous
Are nonspontaneous processes impossible?
No
Can a nonspontaneous process become spontaneous?
Yes, under a change in surrounding conditions OR if paired with another spontaneous process
Kinetics have to do with the ____________ and _______ of a reaction while thermodynamics have to do with the __________ and ___________ of a reaction
Intermediate states, speed
Initial and final states, spontaneity
Are all spontaneous processes fast?
No, spontaneous only indicates direction and extent not rate
__________ is the spreading out of energy.
entropy (S)
In the equation S = K · ln(W) what is W?
The number of energetically equivalent ways to arrange components in a system / microstates within a macrostate
A given set of conditions (P,V,T) describes a system’s __________ and remains constant as long as conditions are constant. The __________ describes the exact internal energy distribution of a system
macrostate
microstate
Increased entropy of a state means ________ dispersal of energy
greater
For any spontaneous process, how must the S of the universe be affected?
the entropy of the universe MUST increase
A chemical reaction will proceed in the direction that ____________ of the universe
increases the entropy
Rank the states of matter from lowest to highest entropy
solid < liquid < gas
When determining the change in entropy of a gaseous reaction . . .
final gaseous mols - initial gaseous mols UNLESS you are working with a phase change of a single compound
What are the units of entropy?
Joules/Kelvin
Equation to determine the change in ΔS universe
ΔS universe = ΔS system + ΔS surroundings
Exothermic processes (-ΔH) ________ ΔS surroundings
increase
Endothermic processes (+ΔH) ___________ ΔS surroundings
decrease
The greater the temperature of the surroundings, the ________ the increase in entropy because . . .
smaller
entropy represents the energy dispersed in a sample of matter PER unit temp.
What is the formula for ΔS surroundings?
ΔS surr. = (-ΔH system)/T
In kelvin at constant pressure and temp.
a process the emits heat is ____________ with a _______ ΔH system but _________ ΔH surroundings
exothermic
negative
positive
a process the absorbs heat is ____________ with a _______ ΔH system but _________ ΔH surroundings
endothermic
positive
negative
ΔS° system = . . .
∑S° products - ∑S° reactants
Given only the change in system energy, how would you calculate ΔS universe?
ΔS universe = ΔS system - (ΔH system/T)
_______ can be used to relate entropy to enthalpy of a system using the equation . . . (hint: GHAST)
Gibbs free energy
ΔG = ΔH - TΔS
How is ΔG related to the enthalpy of the universe?
ΔG = -T · ΔS universe
A decrease in Gibbs (ΔG < 0) corresponds to a _______ process
spontaneous
An increase in Gibbs (ΔG > 0) corresponds to a __________ process
nonspontaneous
The MORE negative ΔG, the more ___________ a process
spontaneous
The temperature at which ΔG changes sign indicates . . . can be determined by setting ΔG = 0 in the equation . . .
Where a reaction goes from spontaneous to nonspontaneous and vise verse.
ΔG = 0 = ΔH - TΔS
The _________ is the change in entropy for a process in which reactants and products are in the standard states
Standard ΔS° rxn
ΔS° rxn = _______________________
with standard molar entropy values (S°) typically given by table
∑np S° products - ∑nr S° reactants
where np and nr represent the stoichiometric coefficients for each product reactant
The entropy of a perfect crystal at 0° K is equal to _________ because . . .
0
it is the only possible way to arrange components, and too cold for vibrations
At 25°C, the standard entropy of any substance is the energy dispersed into __________ of the substance at that temp.
one mol
The greater the molar mass of a compound, the _________ the entropy BUT under what condition?
greater
only for compounds all in the same state
Allotropes with more ridged structures such as diamond have ________ entropy and those that are more amorphous
less
Entropy increases with _________ molecular complexity, i.e. more atoms, bonds, lone pairs
increasing
The dissolution of a crystalline solid results in an _________ in entropy
increase
ΔG° rxn = _______________________
= ΔH°rxn - TΔS°rxn
= ∑np G° products - ∑nr G° reactants
If a chemical equation is multiplied by some factor, ΔGrxn is . . .
multiplied by the same factor
If a chemical equation is reverse, ΔGrxn . . .
changes signs
If a chemical equation is represented as its elementary steps, ΔGrxn overall is the ____________ of each steps’ ΔG
sum
When ΔG°rxn is positive it represents the _____________________________________
minimum amount of energy required for the reaction to occur
How do you relate standard state ΔG°rxn to nonstandard state?
ΔGrxn = ΔG°rxn + RT · ln(Q)
- Q reaction quotient
- T in kelvin
- R = 8.314 J/mol K
ΔG° rxn = __________ given the equilibrium constant K
-R · T · ln(K)
When K < 1, ln(K) is ________ and ΔG° rxn is __________. Under standard conditions (when Q=1), the reaction is spontaneous in the _________ direction
negative
positive
reverse
When K > 1, ln(K) is ________ and ΔG° rxn is __________. Under standard conditions (when Q=1), the reaction is spontaneous in the _________ direction
positive
negative
forward
