Ch. 19: Chemical Thermodynamics

Question 1

What is a spontaneous process?

Answer 1

happens on its own without any outside assistance

Question 2

Are spontaneous processes reversible or irreversible?

Answer 2

ALWAYS irreversible

Question 3

What is a nonspontaneous process?

Answer 3

the reverse of any spontaneous process | needs outside assistance

Question 4

What is the direction of any spontaneous changes in chemical systems determined by?

Answer 4

loss of energy

Question 5

Are all chemical and physical changes endothermic or exothermic?

Answer 5

EXOthermic

Question 6

What is a reversible process?

Answer 6

can restore a system back to its original state with no changes to its surroundings

Question 7

What is an irreversible process?

Answer 7

one that leaves the surroundings somehow changed when the system is restored to its original state

Question 8

What type of process are REAL processes?

Answer 8

spontaneous processes = IRREVERSIBLE processes

Question 9

What is entropy?

Answer 9

degree of disorder or randomness

Question 10

What does entropy measure?

Answer 10

the tendency for the energy to spread = reducing its ability to accomplish work

Question 11

What is the Second Law of Thermodynamics?

Answer 11

entropy of a universe increases for any spontaneous process

Question 12

What does the “universe” consist of?

Answer 12

surroundings + system

Question 13

What are microstates?

Answer 13

specific microscopic arrangements of atoms/molecules of a thermodynamic state

Question 14

What does “W” represent?

Answer 14

number of microstates

Question 15

What is Boltzmann’s constant?

Answer 15

1.38e-23 J/k

Question 16

What trends must W temperature, volume, and number of molecules follow in order to increase entropy (S)?

Answer 16

W, T, V and number of molecules must increase

Question 17

What are the 3 complex motions can every real molecule undergo?

Answer 17

translational | vibrational | rotational

Question 18

What is translational motion?

Answer 18

movement in one direction

Question 19

What is vibrational motion?

Answer 19

the periodic moving away/toward between atoms in a molecule

Question 20

What is rotational motion?

Answer 20

molecule spins about an axis

Question 21

What decreases entropy in chemical bonding?

Answer 21

formation of new bonds

Question 22

What is the order of entropy between states of matter?

Answer 22

g > l > s

Question 23

What are the 3 processes in which entropy increases?

Answer 23

solids/liquids —-> gases | solids —-> liquids | # gas molecules increases during rxn

Question 24

What is the Third Law of Thermodynamics?

Answer 24

entropy of a pure crystalline substance at temperature absolute 0 is 0

Question 25

What is the relationship between standard molar entropy (Sº) and molecular weight?

Answer 25

Sº increases as MW increases

Question 26

What is Gibbs free energy?

Answer 26

the energy associated with a chemical reaction used to do work

Question 27

What ∆G is associated with any spontaneous reaction? In which way does the reaction go?

Answer 27

∆G < 0 = -∆G | forward direction rxn

Question 28

What ∆G is associated with any NONspontaneous reaction? In which way does the reaction go?

Answer 28

∆G > 0 = +∆G | reverse direction rxn

Question 29

What does ∆G = 0 indicate about a reaction?

Answer 29

it is at equilibrium

Question 30

At all temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , +∆H , -∆S ?

Answer 30

nonspontaneous

Question 31

At all temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , -∆H , +∆S ?

Answer 31

spontaneous

Question 32

At low temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , +∆H , +∆S ?

Answer 32

nonspontaneous

Question 33

At low temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , -∆H , -∆S ?

Answer 33

spontaneous

Question 34

At high temps, what kind of reaction (spontaneous or not) is the following combination: -∆G , +∆H , +∆S ?

Answer 34

spontaneous

Question 35

At high temps, what kind of reaction (spontaneous or not) is the following combination: +∆G , -∆H , -∆S ?

Answer 35

nonspontaneous