Equilibrium

Static Equilibrium

Two opposing forces are balanced and no change occurs

Dynamic Equilibrium

Two opposing processes are balanced and no apparent change occurs(it occurs but you just cant see it)

Equilibrium of liquids in a closed system

Rate of evaporation=rate of condensation

Characteristics of equilibrium 

Observable properties don't change over time, macroscopic properties are constant 

System is closed and temp is constant

Opposing internal processes proceed at equal rates (rxn is reversible)

What doesn't the equilibrium eqn rell us

The number of molecules or atoms present

Facts of equilibrium

Can be approached from either side of the reaction eqn

At eq’m the concentration of reactants and products don't change

Adding a catalyst doesn't affect eq’m concentrations, but eq’m is reached more quickly

When does constant K change in a rxn

Is unique to a reaction

Changing the temperature of an equilibrium reaction will change the ratio of rate constants resulting in a different equilibrium constant

What do you omit when writing k expressions

Solids and liquids

Characteristics of K

When the coefficients of an equation are changed, the value of K is raised to a power equal to the change

Ex. H2+I2→ 2HI K=50.w is turned into ½ H2+ ½ I2 → HI K= 50.2^1/2

If an equilibrium is written reversed, the the new K =1/K

What to do when adding reactions

Their equilibrium constants must be multiplied to give the K of the overall reaction

How does the system shift to accommodate an increase of pressure 

System shifts to the side with fewer gas particles to decrease pressure

How does the system shift to accommodate an decrease of pressure 

System shifts to the side with more gas particles to increase pressure

Le chateliers principles

When a change is imposed on a system in equilibrium, the system will shift in the direction which counteracts the imposed change

How does the system react when heat is added

It will counteract the heat by favoring the reaction which absorbs heat

If the temperature increases the system shifts right to use up heat

How does the system react when heat is removed

If heat is removed, it will counteract this by favoring the reaction which makes heat 

If temperature decreases, the system shifts left to release heat

What is solubility

The mass or volume that will dissolve in a given amount of solvent to form a saturated solution at a given temperature

Soluble salt

More than 10 g of a salt will dissolve per liter

Slightly soluble salt

1 to 10 g of a salt will dissolve per liter

Insoluble salt

Less than 1 g will dissolve per liter

Difference between solubility and concentration

Solubility is the amount of solute per volume of solvent

Concentration is the amount of solute per volume of solution

1:1 salt

S²

1:2 salt

4s³

1:3 salt

27s^4

When can you compare Ksp values

Only if the salt ratios are the same

Bronsted Lowry acid-base theory

Acids are hydrogen ion donors 

Bases are hydrogen ion acceptors 

What does Amphiprotic mean

A substance that can act as an acid or a base

Ex. Water 

Characteristics of Amphiprotic ions

Has hydrogen- can donate

Negatively charged- can accept a proton

Why is water amphiprotic

Very electronegative oxygen has a lone pair which can accept H+

Conjugate base

A bronsted-Lowry acid loses a proton to become a conjugate base

Conjugate acid

A bronsted Lowry base that gains a proton becomes a conjugate acid

Conjugate acid and base rule

Strong acids have very weak conjugate bases

Strong bases have very weak conjugate acids

Strong acids

Ionize to a large extent (almost 100%)

Equilibrium highly favors the product side 

Large K

Weak acids

Ionized to a small extent

Equilibrium favors the reactant size 

Small K

Acid ionization constant

For weak acids only

Strong bases

Dissociates completely in solution

Weak bases

Ionized to a small extent 

Equilibrium favors the reactant side 

Small k

Base ionization constant

For weak bases only

Strong acids

HClO4: perchloric acid

HI: hydroiodic acid

HBr: hydrobromic acid

HCl: hydrochloric acid

HNO3: nitric acid

H2SO4: sulfuric acid

Strong bases

NaOH, KOH

If K » 1(acids and bases)

The accused or base is strong( concept of k doesn't apply, use stoichiometry)

If K «1(acids and bases)

The acid or base is weak, use k to find eq'm concentrations

Kw

Kw= [H3O][OH]

Kw=1×10^-14

Kw=Ka*Kb 

In any aqueous solution, the ion product  [H3O][OH] will always be

10^-14

A weak acid or base has K from

10. ^ -4 to 10. ^ -10

A strong acid or base has K

K more than or equal to 10. ^ -2

The conjugate of a weak acid or base is

Weak acid or base

The conjugate of a strong acid or base

Very weak acid or base

Common ion effect

The solubility of an ionic substance is decreased when another substance is added that contains one ion that is the same

Equivalence point

Amount in moles of base is equal to the amount of acid, in moles

End point

Occurs when the indicator changed colour

In a titration, what is required to reach the end point

The volume of base needed to reach the end point must equal the volume of Base to reach the equivalence point

Ionization

When a molecular compound forms ions

Dissociation

An ionic compound breaks up into its constituent ions in water

Hydrolysis

Splitting by water

The reaction between the separated ions and the water may produce a solution that is acidic, basic, or neutral

Ideal buffer

buffers against h3o+ and oh- equally

What are buffers needed for

To combat external stresses on the system from drastically shifting pH

An acidic buffer

Adding acids causes a shift left

Addition of base causes reaction with h3o to form water and system shifts right

A basic buffer

Addition of bases causes a shift left to use up the added oh

Adding acid causes a shift right to replace the oh reacting with the acid