15.2 Entropy

Question 1

What is Entropy?

Answer 1

distribution of available energy among the particles.
-ordered states with small energy distribution have low entropy
-disordered states with high energy distribution have high entropy

Question 2

Delta S of
Solid to Liquid?

Answer 2

increases (+)

Question 3

What does the universe refer to in entropy?

Answer 3

the system and the surroundings

Question 4

Delta S of
gas to liquid

Answer 4

decreases (-)

Question 5

What is absolute Entropy?

Answer 5

The entropy change of substance taken from standard conditions

Question 6

Equation for Change in Entropy

Answer 6

ΔS0=∑nS0(products)−∑mS0(reactants)

Question 7

Equation for Change in Entropy of Surrounding

Answer 7

ΔS= -ΔH/T (T in Kelvin)

Question 8

Equation for Total Entropy Change

Answer 8

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

Question 9

Why can’t Enthalpy or Entropy alone be used to predict the feasibility of a reaction?

Answer 9

Order may increase in local areas but only at the expense of greater disorder elsewhere in the universe.

Question 10

What is Gibbs Free Energy

Answer 10

measure of energy which is free to do useful work rather than just leave a system as heat

Question 11

Gibbs free energy equation

Answer 11

∆G(system) = ∆H(system) – T∆S(system) < 0

Question 12

at lower temperature what happens to ∆G

Answer 12

G(system) ≈ ∆H(system), as T∆S(system) ≈ 0

Question 13

at higher temperature what happens to ∆G

Answer 13

∆G(system) ≈ –T∆S(system)

Question 14

What does it mean when ∆G is negative?

Answer 14

the reaction is spontaneous

Question 15

Basically what conditions make ∆G feasible?

Answer 15

all reactions which have a positive value of ∆S(system) can be feasible at high
temperatures even if they are endothermic.

Question 16

When can ∆Gf⊖ be used to calculate ∆Greaction

Answer 16

when there is no temp change, (at 298K)

Question 17

What is the ∆Gf⊖ of elements in standard state?

Answer 17

0

Question 18

Equation of ∆Greaction with no temp change?

Answer 18

∆Greaction = ∑∆G⊖f (products) – ∑∆G⊖f (reactants)

Question 19

under what value is ∆Greaction considered to be at equilibrium?

Answer 19

< -30 kj/mol

Question 20

when is ∆Greaction at equilibrium mixture?

Answer 20

0 < ∆Greaction < 30 , 0 > ∆Greaction > -30

Question 21

∆Greaction greatere than +30 kj/mol

Answer 21

spontaneous change impossible no reaction