Chapter 18 Free Energy & Thermodynamics Part 2 Flashcards Preview

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Flashcards in Chapter 18 Free Energy & Thermodynamics Part 2 Deck (21):
1

What are the 3 methods of calculating ΔG^o rxn

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)

2

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

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

3

ΔG^o f of elements is...

Zero

4

ΔG^o f of most compounds is...

Negative

5

Define Standard State

The state of a material at a defined set of conditions

6

Define Nonstandard State

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

7

What is the equation used for Nonstandard States?

ΔGrxn =ΔG^o rxn + RTlnQ

8

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

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

9

Define ΔGrxn

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

10

T/F ΔGrxn varies as composition changes

True

11

How many values does ΔGrxn have for a particular reaction?

ONE

12

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

Standard; one; 0; ΔGrxn

13

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

Equilibrium; -ΔGrxn; 0

14

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

I and II

15

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

ΔGrxn = RT (lnQ - lnK)

16

What does it mean when Q < K?

ΔGrxn < 0, spontaneous, reaction moves to the right

17

What does it mean when Q > K?

ΔGrxn > 0, nonspontaneous, reaction moves to the left

18

What does it mean when Q = K?

ΔGrxn = 0, at equilibrium, reaction moves neither ways

19

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

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

20

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

I and III

21

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

ΔG^o rxn= -RTlnK