Enthalpy, Entropy And Free Energy

Question 1

Entropy

Answer 1

Measure of disorder or randomness

Question 2

Crystalline Solid Entropy

Answer 2

Low
Higher when it melts

Question 3

Entropy Symbols

Answer 3

Entropy = S
Standard Entropy = S°
Change = /\S°

Units = J K-1mol-1

Question 4

Entropy Change of State Graph

Answer 4

• 0 Kelvin S°=0 -particles not moving - perfect order

•Temp Increases = Movement Increases = Disorder Increases

• Vertical Show Change in state
- large increase S° as temp remains constant

• Vertical section for boiling > Vertical section for melting
- gas very disordered

Question 5

Change in Entropy Equation

Answer 5

/\S°= sum of S° products - sum of S° reactants

Question 6

Free Energy Equation

Answer 6

/\G° = /\H° - T/\S°

Question 7

Feasible Reaction

Answer 7

Free energy (/\G°) must be less than 0

Question 8

Free Energy, /\G°, Units

Answer 8

kJmol-1

Question 9

Cpnvert J K-1mol-1 to kJ K-1mol-1

Answer 9

Divide J K-1mol-1 by 1000

Question 10

Determine temperature for reaction to become feasible

Answer 10

Divide /\H° by /\S° (in kJ K-1 mol-1)

T= /\H
/\S°/1000

Question 12

What is /\G° at change of state

Answer 12

0
System at equilibrium

Question 13

Feasibility when /\H negative and /\S negative

Answer 13

/\G may be + or -

Feasible below certain temps

Question 14

Feasibility when /\H negative and /\S positive

Answer 14

/\G always -

Feasible at any temp

Question 15

Feasibility /\ H positive /\S negative

Answer 15

/\G always positive

Not feasible at any temp

Question 16

Feasibility /\H positive /\S positive

Answer 16

/\G may be + or -

Feasible above certain temps

Question 17

Feasibility Exothermic and Endothermic

Answer 17

Exothermic w/ increase entropy - feasible any temp

Endothermic w/ decrease entropy - NOT feasible at any temp