Week Eight

Question 1

Entropy

Answer 1

spontaneous processes tend to proceed from states of low probability to states of higher probabilty
spontaneous processes tend to disperse energy

Question 2

Delta S

Answer 2

Sproducts - Sreactants

Question 3

Spontaneous event

Answer 3

accompanied by an increase in entropy of the system

Question 4

Entropy change of a process

Answer 4

change in heat/ temp

Question 5

Factors that affect entropy

Answer 5

volume
temperature
physical state
number of particles

Question 6

Volume

Answer 6

possible to predict whether delta S is positive or negative

entropy increases with increasing volume for gases

Question 7

Temperature

Answer 7

higher the temp, higher the entropy

Question 8

Physical state

Answer 8

solid –> liquid –> gas

Question 9

Number of particles

Answer 9

when all other things are equal, reactions that increase the number of particles in the system tend to have positive entropy change

Question 10

Second law of thermodynamics

Answer 10

whenever spontaneous event occurs in universe, total entropy of the universe increases

Question 11

Entropy change of universe equation

Answer 11

= entropy change of system + entropy change of surroundings

Question 12

Entropy change for surroundings

Answer 12

equal to heat transferred to surroundings from system / Temp

Question 13

Change in entropy surroundings

Answer 13

change in heat surroundings/ temperature

Question 14

Change of entropy system

Answer 14

• change in heat surroundings/ temperature or - change enthalpy system/ temperature

Question 15

Total entropy change

Answer 15

change of entropy system - change in enthalpy system/ temperature

Question 16

Gibbs free energy

Answer 16

H - T x s

Question 17

Gibbs free energy change

Answer 17

delta H - T x delta S

Question 18

Third Law of thermodynamics

Answer 18

at absolute zero, the entropy of a perfectly ordered pure crystalline substance is zero
provides point at which absolute entropy is known

Question 19

Standard entropy

Answer 19

entropy of 1 mol of a substance determined at standard conditions at a temp of 298K

Question 20

Entropy positive - enthalpy positive

Answer 20

spontaneous at high temps, non spontaneous at low temps

Question 21

Entropy positive - enthalpy negative

Answer 21

spontaneous at all temps

Question 22

Entropy negative - enthalpy positive

Answer 22

non spontaneous at all temps

Question 23

Entropy negative - enthalpy negative

Answer 23

non spontaneous at high temps, spontaneous at low temps

Question 24

Standard gibbs free energy change

Answer 24

when change in gibbs is determined at standard pressure, this is called standard free energy change

Question 25

Standard free energy change

Answer 25

change in Heat at standard - temp x change in entropy at standard

Question 26

Maximum conversion of chemical energy into work

Answer 26

can only occur if a process is thermodynamically reversible Requires the system to operate at equilibrium constantly

Question 27

Equilibrium

Answer 27

when a reactions forward and reverse reactions are occuring at same speed no net change in overall composition

Question 28

Kc

Answer 28

equilbrium constant

Question 29

Kc equation

Answer 29

Kc = {C}^c {D}^d ---------------------------- {A}^a {B}^b

Question 30

temperature effect on Kc

Answer 30

dependent on temp so temp is always specified

Question 31

Qc

Answer 31

reaction quotient | same as equilbirum equation but not all values are at equilbrium

Question 32

Kc rules

Answer 32

can only have one positive value at specific temp

Question 33

QC rules

Answer 33

can have multiple positive values

Question 34

Qc = Kc

Answer 34

at equilibrium

Question 35

Qc> Kc

Answer 35

when system reacts to use up all products and generate more reactants

Question 36

Qc< Kc

Answer 36

when system reacts to use up all reactants and generates more products

Question 37

Kp

Answer 37

uses partial pressure to specify the quantity of the two gases

Question 38

Kp equation

Answer 38

Kp = kc x (RxT / standard pressure)^ delta n gas

Question 39

number of moles

Answer 39

n/1 mol

Question 40

Delta n gas

Answer 40

(number of moles of gaseous products) - number of moles of gaseous reactants)

Question 41

Kc'

Answer 41

1/ Kc | when reaction is flipped

Question 42

Kc< 1

Answer 42

more reactant

Question 43

Kc = 1

Answer 43

same amounts of products and reactants

Question 44

Kc > 1

Answer 44

more product

Question 45

Homogeneous

Answer 45

all reactants and products are in same phase

Question 46

Heterogeneous

Answer 46

more than one phase

Question 47

Kc - structure of molecules

Answer 47

cant include the concentration of pure solids or pure liquids

Question 48

Pure liquids and solids at constant temp

Answer 48

ratio of amount of substance to volume of substance is constant