chap 17 quiz 2-midterm

Question 1

What is a spontaneous process

Answer 1

A spontaneous process is something that occurs without any outside intervention

Question 2

What is the driving force in a spontaneous process

Answer 2

An increase in entropy (S of universe)

Question 3

What is entropy

Answer 3

Measure of the randomness or disorder of a system

Question 4

Explain the expansion of gases

Answer 4

The expansion of gases is a spontaneous process because it leads to an increase in positional entropy

Question 5

What is the entropy for all states

Answer 5

Gases are more disordered than liquids than solids

Ssolid < Sliquid < Sgas

ΔS = Sf-Si

Question 6

What is the first law of thermodynamics

Answer 6

Energy can be converted but never created or destroyed

Question 7

What is the second law of thermodynamics

Answer 7

All spontaneous processes produce an increase in the entropy of the universe

Question 8

What is the sign of the entropy of the universe

Answer 8

Positive

Question 9

State basic formulas and how to get to ΔG

Answer 9

ΔSuniverse = ΔSsystem + ΔSsurroundings
ΔSsurroundings = -ΔH/T 
-TΔSuniverse = ΔH -TΔSsystem 
-TΔSuniverse = ΔG 
ΔG = ΔHsystem - TΔSsystem

Question 10

What does the sign of ΔG mean

Answer 10

ΔG < 0 = process is spontaneous
ΔG > 0 = process is not spontaneous
ΔG = 0 = process is at equilibrium

Question 11

What do signs of ΔS and ΔH mean

Answer 11

ΔS = + & ΔH = - = spontaneous at all temperatures
ΔS = + & ΔH = + = spontaneous at high temperatures (exothermicity is unimportant)
ΔS = - & ΔH = - = spontaneous at low temperatures (exothermicity is dominant)
ΔS = - & ΔH = + = not spontaneous at any temperature (reverse reaction is spontaneous at all temperatures)

Question 12

What is the third law of thermodynamics

Answer 12

The entropy of a perfect crystal at 0K = zero
Allows the absolute values for entropies of compounds and elements to be determined (entropy values are expressed in relation to the standard state)

Question 13

State formula for standard entropy values

Answer 13

ΔSreaction = Σ npS(products) - Σ nrS* (reactants)

Question 14

State formula for ΔG*

Answer 14

ΔG* = ΔH* - TΔS*

Question 15

State the standard conditions

Answer 15

For compounds
Gases = 1atm
Condensed states = pure liquid or solid
Solutions = concentrations of 1M
For elements
Conditions of 1atm and 25c
ΔGf of elements in standard states = 0 (diatomics!!)

Question 16

State formula for standard gibbs energy of formation

Answer 16

ΔG* = Σ npΔGf (products) - Σ nrΔGf (reactants)

Question 17

State formula for nonstandard gibbs energy

Answer 17

ΔG = ΔG* + RTln(Q)
ΔG = ΔG* + RTln(k)
K=Kc for aq
K=Kp for gases

Question 18

What does sign of ΔG* mean in relation to K

Answer 18

ΔG* < 0, K > 1 = equilibrium lies closer to products

ΔG* > 0, K < 1 = equilibrium lies closer to reactants

Question 19

State the formula for temperature dependance of K

Answer 19

ln K2/K1 = ΔH/R (1/T1 - 1/T2)