Chapter 10 - Entropy

Question 1

Entropy is a measure of disorder of a system. How does entropy (S) inc and dec?

Answer 1

• order up-S down

* disorder up-S up

Question 2

Define entropy in each of the states.

Answer 2

Ssolid

Question 3

Is Entropy ever negative?

Answer 3

No. ΔS can be tho.

Question 4

What is ΔS in terms of microstates?

Answer 4

ΔS = kln(Wf/Wi)

*W- microstates
k- 1.38e-23

Question 5

What is the 2nd Law of Thermodynamics?

Answer 5

• Spontaneous: ΔSuniv = ΔSsys + ΔSsurr > 0

* Equilibrium: ΔSuniv = ΔSsys + ΔSsurr = 0

Question 6

What is the standard entropy of reaction (1 atm, 25°C)?

Answer 6

ΣS (products) – ΣS (reactants)

Question 7

When judging entropy in a Chem Eq what to look for?

Answer 7

Judge by number of moles on each side. (Product-reactant) If it is same, Probably a small net total S.

Question 8

What is the 3rd Law of Thermodynamics?

Answer 8

Substance is zero at absolute zero of temperature.

Question 9

Define Endo and Exo in terms of entropy.

Answer 9

• Endo ΔSsurr > 0

* Exo ΔSsurr

Question 10

Does decrease in enthalpy guarantee a spontaneous reaction?

Answer 10

It does NOT guarantee.

Question 11

Remember to S = J/K and H = kJ. CONVERT!!!!

Answer 11

J

Question 12

How to tell spontaneity from ΔG?

Answer 12

• ΔG (+) - nonspontaneous
• ΔG (–) - spontaneous
• ΔG (0) - neither