4.4 Entropy and Gibbs free energy

Question 1

what can be exchanged in an OPEN SYSTEM

Answer 1

energy and matter

Question 2

what can be exchanged in a CLOSED SYSTEM

Answer 2

energy only

Question 3

what can be exchanged in an ISOLATED SYSTEM

Answer 3

neither energy nor matter

Question 4

entropy is a measure of…

Answer 4

possible arrangements with the same overall energy

Question 5

entropy change equation

Answer 5

∆S = S(products) − S(reactants)

Question 6

2nd law of thermodynamics

Answer 6

entropy of the universe is always increasing

∆S(system) + ∆S(surroundings) = ∆S(universe) > 0

Question 7

increasing temperature…

Answer 7

increases kinetic energy > increases possible arrangements > increases entropy

Question 8

increasing concentration…

Answer 8

increases possible arrangements > increases entropy

Question 9

why entropy of liquid > solid

Answer 9

non-fixed vs fixed structure

Question 10

why entropy of gas > liquid

Answer 10

continual movement and occupying more volume

Question 11

what is solid dissolution and why does it increase entropy

Answer 11

a solid solute dissolves in a solvent to form an aqueous solution

solute particles have more possible arrangements

Question 12

spontaneous reaction

Answer 12

any natural reaction that doesn’t need external energy

Question 13

3rd law of thermodynamics

Answer 13

the THEORETICAL entropy of a perfect crystal (lattice) is zero

only 1 arrangement; no vibration; no kinetic energy

Question 14

standard enthalpy

Answer 14

standard conditions 25C and 1 bar pressure

∆Sdeg = ΣSdeg(products) - ΣSdeg(reactants)

Question 15

Gibbs free energy equation and all units involved

Answer 15

∆G = ∆H - T∆S

∆G in kJ/mol
∆H in kJ/mol
T in Kelvins (careful)
∆S in J K-1 mol-1 (careful)

Question 16

∆G < 0, ∆G > 0
and ∆G = 0

Answer 16

if ∆G = neg, it’s spontaneous
if ∆G = pos, it’s not spontaneous

if ∆G = 0, the reaction is at equilibrium (module 5)

Question 17

reaction is spontaneous at all T when:

Answer 17

∆H < 0 (neg)
T∆S > 0 (pos)

Question 18

reaction is NOT spontaneous at any T when:

Answer 18

∆H > 0 (pos)
T∆S < 0 (neg)

Question 19

if ∆H = pos,
reaction is spontaneous at HIGH T when:

Answer 19

∆H < T∆S
so ∆H - T∆S < 0 if T is large

Question 20

if ∆H = neg,
reaction is spontaneous at LOW T when:

Answer 20

∆H > T∆S
so ∆H - T∆S < 0 if T is small