CHEMICAL EQUILIBRIA

Question 1

What does the activity of a compound tell us?

Answer 1

The activity of a compound tells us how the free energy/chemical potential of a compoud varies with the progress of the rxn

Question 2

What is the activity of a gas?

Answer 2

P° = standard pressure of 1 atm

Question 3

What is the activity of a pure solid or liquid?

Answer 3

Question 4

What is the activity of a solution?

Answer 4

C° = standard concentration of 1 M

Question 5

What species are used in a mass action expression?

Answer 5

Gaseous and aqueous species only

Question 6

What is the formula for mass action expression?

Answer 6

Q = products / reactants = K (when dG = 0)

Question 7

What is Q?

Answer 7

Q is the reaction quotient, a current or “right now” condition and can be calculated at any point

Question 8

What is K?

Answer 8

Q converges into the equilibrium constant (K) as the system reacts and adjusts

Question 9

The equilibrium constant (K) is constant unless what changes?

Answer 9

Temperature

Question 10

What does it mean when K > 1?

Answer 10

K > 1 ; product favored (rxn moves forward)

Question 11

What does it mean when K < 1?

Answer 11

K < 1 ; reactant favored (rxn moves in reverse)

Question 12

How is K manipulated?

Answer 12

1. When the rxn is reversed, K becomes 1/K
2. Whe the rxn is doubled, K becomes K^2

Question 13

What does it mean when Q < K?

Answer 13

Q < K ; too many reactants, so the rxn tends to move forwards

Question 14

What does it mean when Q = K?

Answer 14

Q = K ; the rxn is at equilibrium (dG = 0)

Question 15

What does it mean when Q > K?

Answer 15

Q > K ; there are too many products, so the rxn tends to move in reverse

Question 16

What does the plot of Gibbs free energy look like when dG° rxn < 0

Answer 16

Question 17

What does the plot of Gibbs free energy look like when dG° rxn > 0

Answer 17

Question 18

At what points on both these plots is the rxn reactant heavy?

Answer 18

Q < K at points 1 and 3

Question 19

At what points on both these plots is the rxn product heavy?

Answer 19

Q > K at points 3 and 3

Question 20

What is the formula for dG rxn?

Answer 20

Question 21

What is the formula for dG° rxn?

Answer 21

Question 22

What is K when dG is < 0?

Answer 22

K > 1 ; products are favored

Question 23

What is K when dG is > 0?

Answer 23

K < 1 ; reactants are favored

Question 24

What is Le Chatelier’s Principle?

Answer 24

Le Chatelier’s Principle states that when a chemical system at equilibrium experiences a change, the equilibrium shifts to counteract the imposed change and a new equilibrium established

Question 25

What happens when reactants are added to a reaction?

Answer 25

When reactants are added, the rxn shifts to the product side

Question 26

What does adding reactants result in?

Answer 26

Q \< K

Question 27

What happens when products are added?

Answer 27

When products are added, the rxn shifts towards the reactants

Question 28

What does adding products result in?

Answer 28

Q \> K

Question 29

What happens when reactants are removed?

Answer 29

When reactants are removed, the rxn shifts to the reactant side

Question 30

What happens when products are removed?

Answer 30

When products are removed, the rxn shifts to the product side

Question 31

What happens when volume increases?

Answer 31

Increase in volume = decrease in pressure = shifts to side with greater gaseous moles

Question 32

What happen when the volume decreases?

Answer 32

Decrease in volume = increase in pressure = shifts to side with least gaseous moles

Question 33

What happens when an inert gas is added at constant pressure?

Answer 33

Volume increases

Question 34

What happens when an inert gas is added at constant volume?

Answer 34

Pressure increases, however, there is no effect

Question 35

What happens when temperature is added to an endothermic reaction?

Answer 35

Increase in temperature for an endothermic rxn (heat is reactant) = shifts to products = K increases

Question 36

What happens when temperature is added to an exothermic reaction?

Answer 36

Increase in temperature for an exothermic rxn (heat is product) = shifts to reactants = K decreases

Question 37

What is the Van't Hoff Equation?

Answer 37

Question 38

What is the formula for Kp?

Answer 38

Kp = Kc (RT) ^ dn