Lecture 20- Equilibrium 3

Question 1

Delta G

Answer 1

• G must be less than zero for a reaction to proceed in a given direction
• G is the maximum amount of work that can be done by a system
• A system is at equilibrium when it is no longer able to do work (G=0)
• Although forward and reverse reactions continue to take place at equilibrium, net changes in concentration are not possible
• Keq is directly related to G

Question 2

When G

Answer 2

• The process favors products at equilibrium
• Keq > 1
• The reaction will proceed to equilibrium in either direction
• The reaction is considered to be “exergonic”

Question 3

Endergonic reactions

Answer 3

• G>0
• The process favors reactants at equilibrium
• K 0) will produce products if the system initially contains only reactants
• If the products are removed, the equilibrium will shift in order to produce more produces (Le Chatelier)

Question 4

What is G again?

Answer 4

• Standard state for G tells us that all species exist as pure substances, all gases have partial pressure of 1 atm, all aqueous species have 1 M concentrations, and the temperature of the system is 298 K
• Because equilibrium exists at other temperatures, we can use the same equations from this lecture to calculate G at other temperatures (Gt)
• G is the maximum amount of work that can be done by a system as it moves from 100% reactions in their standard states to 100% products in their standard states
• G is the maximum amount of work that can be done by a system as it moves from 100% reactants (1 M concentrations and 1 atm) to 100% products (1 M concentrations and 1 atm) at non-standard temperatures

Question 5

Relating G to Keq

Answer 5

• G= -RTlnKeq
• Keq= e^-G/RT
• G must be in J/mol
• R=8.134 J/molK
• T must be in K
• Keq must be calculated using partial pressures for gases and molar concentrations for aqueous species

Question 6

Estimation of Keq

Answer 6

• At 298 K, RT=2400J/mol

- G» 2400J/mol, then K>1

Question 7

Estimation of Keq important chart

Answer 7

• G>0 and K20kj and K1 = mostly products

- G >1 = virtually all products

Question 8

+G

Answer 8

not TDF, favors reactants, lies to left

Question 9

-G

Answer 9

TFD, favors products, lies to right

Question 10

kj to j

Answer 10

1 kj=1000j