Chapter 11 - Chemical Equilibrium

dynamic equilibrium

Rate of forward reaction will occur at the same rate as that of the reverse reaction

No

Once equilibrium is reached, do the forward and reverse reactions stop?

Not necessarily

Do concentrations of reactants and products have to be equal at the time of equilibrium?

Gibbs' free energy formula including equilibrium constant

∆G° = -RTln(Keq)

Keq < 1

Greater concentration of reactants than products at equilibrium

Keq = 1

Ratio of products to reactants at equilibrium is equal

Delta G is positive, more reactants

When Keq < 1, is ΔG° positive or negative?

Delta G = 0

When Keq = 1, is ΔG° positive or negative?

ΔG° is negative, there are more products

When Keq > 1, is ΔG° positive or negative?

Equilibrium Constant

Based off of concentrations once reaction has reached equilibrium

Reaction quotient

ses concentrations at any point in time during a reaction other than equilibrium

Q < Keq

There is a higher concentration of reactants than there would be at equilibrium, as such the system shifts more towards the forward reaction to reach equilibrium

Q = Keq

The reaction is in dynamic equilibrium

Q > Keq,

There is a higher concentration of products than there there would be at equilibrium, as such the system more towards the reverse reaction to reach equilibrium

Liquid and solids

What type of reactants and products are excluded from calculating equilibrium constant?

Le Châtelier's principle

A system will shift in a direction that restores the equilibrium state in the presence of changes in concentration or in the temperature of the system

forward

If reactants are added, what direction would the reaction shift?

Reverse

If reactants are removed, what direction would the reaction shift?

Reverse

If products are added, what direction would the reaction shift?

Shift towards the side with less moles

If pressure is added to a system resulting in a decrease in volume, how would the equilibrium shift?

Shift towards the side with greater moles

If pressure is removed from a system resulting in an increase in volume, how would the equilibrium shift?

Reactant

If a reaction is endothermic in the forward direction, would heat be considered a reactant or a product?

Product

If a reaction is exothermic in the forward direction, would heat be considered a reactant or a product?

Shift Left

If you lower the temperature in an endothermic forward reaction, what direction would the system shift?

Shift Left

If you increase the temperature in an exothermic forward reaction, what direction would the system shift?

solubility product constant (Ksp)

Used to figure out direction in which reaction will proceed, but also the saturation of the solution and whether or not precipitation will occur

Q = Ksp

What relationship between Q and Ksp would suggest a saturated reaction mixture?

Q > Ksp

What relationship between Q and Ksp would suggest a supersaturated reaction mixture?

Q < Ksp

What relationship between Q and Ksp would suggest an unsaturated reaction mixture?

Precipitation

Q > Ksp. Reaction is currently supersaturated and will proceed in reverse reaction to result in _________

amphoteric

A substance that can act as both an acid and a base, depending on what it is reacting with

Acidic dissociation constant (Ka) formula

Ka = [H+][A-]/[HA]

Basic dissociation constant (Kb) formula

Kb = [OH-][HB+]/B]

Shift left

How would the following reaction shift if HCl is added? HA (aq) + H2O (l) ⇄ H3O+ (aq) + A- (aq)

Shift right

How would the following reaction shift if NaOH is added? HA (aq) + H2O (l) ⇄ H3O+ (aq) + A- (aq)

shift right

How would the following reaction shift if HA is added? HA (aq) + H2O (l) ⇄ H3O+ (aq) + A- (aq)

Shift left

How would the following reaction shift if A- is added? HA (aq) + H2O (l) ⇄ H3O+ (aq) + A- (aq)

Positive

K_eq < 1, then ln(K_eq) is negative, making the ΔG° _______

Equal

K_eq = 1, then ln(K_eq) is zero, making the ΔG° ____ to zero

Negative

K_eq > 1, then ln(K_eq) is positive, making the ΔG° ______ (spontaneous)

Reactants

ΔG° > 0, formation of ______ is favored at equilibrium. 

Products

ΔG° < 0, formation of ______ is favored at equilibrium. 

Irreversible Reactions

Denoted by a unidirectional arrow

Reversible Reactions

Denoted by a bidirecitonal arrow; meaning reactants can convert into products and products can convert into reactants

Dynamic Equilibrium

When the rate of the forward reaction is equal to the rate of the reverse reaction

Same

In a dynamic equilibrium, the forward and reverse reactions proceed at the _____ rate

Do not

The forward and reverse reactions _____ stop once equilibrium is reached

Not always

The concentrations of the reactants and products are ________ equal at the equilibrium

Law of Mass Action

States that the rate of the forward and reverse reaction is proportional to the product of the concentrations of the reactants and products

Equilibrium constant

Allows us to quantify the concentrations of reactants and products for a system in equilibrium under constant temperature

kp

Represents the equilibrium constant of gaseous systems, expressed in partial pressures

Keq < 1

There is a greater concentration of reactants than products

Keq > 1

There is a greater concentration of products than reactants

Keq = 1

Ratio of reactants to products is equal at equilibrium

Positive

When Keq < 1, delta G will be ________

0

When Keq = 1, delta G will be equal to ______

Negative

When Keq > 1, Delta G will be ________

Reactants

When Q < Keq, there is a higher concentration of _______ than there is at equilibrium

Equilibrium

Q = Keq, the reaction is in dynamic _______

Products

When Q > Keq, there is a higher concentration of _______ than there is at equilibrium

Inert Gas

Part of noble gases; it does’t have that much power to do anything

More soluble

Higher Ksp

Less soluble

Lower Ksp