Chapter 18 Free Energy & Thermodynamics Part 2

Question 1

What are the 3 methods of calculating ΔG^o rxn

Answer 1

I) Use tabulated ΔH^o and ΔS ^o and use equation
ΔG^o rxn = ΔH^o rxn - TΔS^o rxn
II) Use ΔG^o rxn for each step
III) Use tabulated free energy of formation (ΔG^o f)

Question 2

Define Standard Free Energy of Formation (ΔG^o f)

Answer 2

The change in free energy when 1 mole of a compound in its standard state forms from its elements in their standard states

Question 3

ΔG^o f of elements is…

Answer 3

Zero

Question 4

ΔG^o f of most compounds is…

Answer 4

Negative

Question 5

Define Standard State

Answer 5

The state of a material at a defined set of conditions

Question 6

Define Nonstandard State

Answer 6

When you can calculate free energy by calculating the free energy change of a reaction at standard conditions

Question 7

What is the equation used for Nonstandard States?

Answer 7

ΔGrxn =ΔG^o rxn + RTlnQ

Question 8

In the Nonstandard State equation
ΔGrxn =ΔG^o rxn + RTlnQ
What does Q, T, and R represent?

Answer 8

Q - reaction quotient
T - temperature in Kelvin
R - gas constant (8.314 J/mol x k)

Question 9

Define ΔGrxn

Answer 9

Represents the total free energies of all substances in the reaction mixture at any particular system composition

Question 10

T/F ΔGrxn varies as composition changes

Answer 10

True

Question 11

How many values does ΔGrxn have for a particular reaction?

Answer 11

ONE

Question 12

Under __________ conditions, Q will always equal to _____, ln(1) = _______, and ΔG^o rxn = ________

Answer 12

Standard; one; 0; ΔGrxn

Question 13

Under __________ conditions value of RT lnQ will be equal to _________, and ΔGrxn = _________

Answer 13

Equilibrium; -ΔGrxn; 0

Question 14

Which of the following is true for a spontaneous process?
I) ΔSuniverse > 0 
II) ΔG < 0 
III) K = 1 
IV) Q = 1

Answer 14

I and II

Question 15

What is the equation used to relate ΔG^o rxn to Equilibrium Constant K to get overall ΔGrxn?

Answer 15

ΔGrxn = RT (lnQ - lnK)

Question 16

What does it mean when Q < K?

Answer 16

ΔGrxn < 0, spontaneous, reaction moves to the right

Question 17

What does it mean when Q > K?

Answer 17

ΔGrxn > 0, nonspontaneous, reaction moves to the left

Question 18

What does it mean when Q = K?

Answer 18

ΔGrxn = 0, at equilibrium, reaction moves neither ways

Question 19

For the given reaction when Q = 8.5x10^-6 and K = 6.4x10^-5, what describes the ΔG of the reaction?

Answer 19

Q < K, so ΔGrxn < 0, reaction is spontaneous

Question 20

Which is always true when a system is at equilibrium?
I) ΔG = 0
II) Q = 1
III) Q = K

Answer 20

I and III

Question 21

What is the equation used to relate ΔG^o rxn to Equilibrium Constant K?

Answer 21

ΔG^o rxn= -RTlnK