G Chem: Equilibrium, Acids, And Bases

Front 1

Equilibrium Constant

Back 1

K = [products] / [reactants]
when reaction is at equilibrium

Coefficients become exponents

Solids omitted

Liquids omitted when they are the solvent (constant concentration)

K is only dependent on temperature

Front 2

Reaction Quotient

Back 2

Q What's happening when reaction is not at equilibrium

follows same rules as K

except dependent on temperature and concentration

Front 3

Le Chatelier's Principle

Back 3

a system in equilibrium will shift to minimize that stress.

Stress cannot be entirely eliminated. Only minimized.

stress can be changes in concentration, volume, pressure, and temperature

Front 4

Concentration or partial pressure (of individual reagents) effects on reaction at K

Back 4

changing the partial pressure of a gas has the same effect as changing the concentration of a substance.

Front 5

total pressure or volume effects reaction at K

Back 5

P and V behave inversely of each other (i.e. increasing pressure is decreasing total volume)

when space is decreased reaction will be pushed in direction with less molecules of gas (sum of coefficients) ignoring solids and solvents

Front 6

Temperature effects on reaction at K

Back 6

must know if reaction is exo or endothermic (usually given in passage)

endothermic - heat is reactant ∆H +

exothermic - is product ∆H -

When heat is treated as a product or reactant, adding or subtracting heat is akin to changing the concentration of a product or reactant

Front 7

Multiple Equilibria

Back 7

If one reaction shifts in a multiple equilibria equation then steps will shift in the same direction

Front 8

Multiple equilibria of CO₂ + H₂O

Back 8

CO₂ (g) + H₂O (l) →
CO₂(aq) + H₂O (l) →
H₂CO₃ (aq) →
H⁺ (aq) + HCO₃⁻ (aq) →
2H⁺ (aq) + CO₃²⁻ (aq)

Front 9

Solubility Equilibria (Ksp vs S)

Back 9

S = molar solubility = maximum molar concentration that can dissolve

Ksp = Solubility product =equilibrium constant for dissociation reaction

Need rxn equation

write equilibrium equation

plug coefficients in as concentrations times variable

Front 10

Qsp vs. Ksp problems

Back 10

shows whether precipitate will form

if Qsp > Ksp then supersaturated
excess will precipitate out

if Qsp = Ksp then in equilibrium (saturated)

if Qsp < Ksp then unsaturated; more can be added without precipitation

Front 11

Common ion effect

Back 11

a salt's solubility will decrease if you try to add it to a solution that already contains a common ion

a salt's solubility will increase if it is added to to a solution where the ion is removed by something

Front 12

Acid Definition

Back 12

Arrhenius - donate H⁺

Bronsted Lowry - donate H⁺

Lewis - accept e⁻

Referred to as electrophile

Front 13

Base definition

Back 13

Arrhenius - donate OH⁻

Bronsted Lowry - accept H⁺

Lewis - donate e⁻

Known as nucleophiles

bases are ligands and chelates - donor in coordinate covalent bond

Front 14

Acid Base recognition

Back 14

usually electronegative atom bonded to hydrogen (EN-H)
ex. EtOH, HCl
-Atoms without H can still be acids if they
they are electron deficient or with large positive
charges
ex. Al³⁺, BF₃(incomplete octet)

Bases generally have electronegative atom with lone pairs (EN:)
ex. :NH₃, H₂O:
-atoms without lone pairs cannot be basic

Front 15

amphoteric

Back 15

substance that exhibits both acidic and basic properties.

Usually one is stronger than the other

ex. NH₃, H₂O: water is actually about equal in acidic and basic properties

Front 16

Acid Dissociation (qualitative)

Back 16

HA + H₂O ↔ H₃O⁺ + A⁻

conjugates are compounds that differ by ONE H⁺

stronger acids dissociate more completely (Equilibrium favors products)

Weaker acids dissociate less completely (Equilibrium favors reactants)

Front 17

Base Dissociation (qualitative)

Back 17

A⁻ + H₂O ↔ HA + OH⁻

conjugates are compounds that differ by ONE H⁺

Stronger base associates more completely with H⁺
(Equilibrium favors products)

Weaker base associates less completely with H⁺
(Equilibrium favors reactants)

Front 18

Acid Dissociation (quantitative)

Back 18

HA + H₂O ↔ H₃O⁺ + A⁻

Acid dissociation constant (equilibrium constant)

Ka = [H₃O⁺][A⁻] / [HA]

Larger Ka means higher acidity and lower pKa

pKa = -Log Ka

Front 19

Base Dissociation (quantitative)

Back 19

A⁻ + H₂O ↔ HA + OH⁻

Base dissociation constant (equilibrium constant)

Kb = [HA] [OH⁻] / [A⁻]

pKb = -log Kb

As Kb increases acidity increases pKb decreases

Front 20

Acid and Base Charge Trend

Back 20

more positive charge increases acidity

more negative charge increases basicity

Front 21

Acid Base electronegativety trend

Back 21

H bonded to more electronegative means stronger acid

Less electronegative increases basicity

This trend only works alongs periods

Front 22

Acid Base size trend

Back 22

Larger atoms increase acidity

Smaller atoms increases basicity

trend only works within groups

Front 23

Acid Base Resonance Trend

Back 23

more atoms in the conjugated system increases acidity

Less atoms in conjugated system increases basicity (electrons that are more localized are easier to donate)

Front 24

Acid base induction trend

Back 24

Electron withdrawing groups increase acidity

closer proximity of electron withdrawing group (to the acidic group) increases acidity

Electron donating groups increase basicity

proximity of donoating group increases basicity as well

Front 25

Strong vs weak acids

Back 25

Strong acids completely dissociate
- Ka > 1
- conjugate base is so weak it's not basic

Weak Acids partially dissociate
- Ka < 1
- conjugate base is a stronger base

Front 26

Strong vs weak bases

Back 26

Strong bases completely dissociate
- Kb > 1
- conjugate acid so weak not even an acid

Weak Bases partially dissociate
- Kb < 1
- conjugate acid is a stronger acid

Front 27

List of common strong acids

Back 27

H₂SO₄ (diprotic)
HClO₄
HClO₃
HNO₃
HCl
HBr
HI

Front 28

List of Common Strong Bases

Back 28

O²⁻ (diprotic as it can accept two Protons)

Group I and Group II Salts of the following anions
OH⁻
OR⁻
NH₂⁻
NR₂⁻
H⁻
R⁻

Front 29

Common Weak Acids

Back 29

HF
HCN
H₂CO₃
NH₄⁺
RNH₃⁺
PhOH (phenol)
RCOOH
Small very positive metal cations (Fe³⁺, Al³⁺)
Electron deficient compounds (BF₃, BeH₂)

Front 30

Common Weak bases

Back 30

F⁻
CN⁻
HCO₃⁻
NH₃⁻
RNH₂
PhO⁻
RCOO⁻

Front 31

Acidic and Basic Salts

Back 31

An acidic salt contains an ion that is a weak acid

Group I and II cations are never acidic

A basic salt contains an ion that is a weak base

Cl⁻, Br⁻, and I⁻ are never basic.

Front 32

∆G at K

Back 32

∆G = -T∆S = 0 at equilibrium