Chemistry Equilibrium, Acid-Base, and Redox Key Concepts

Q > K

Shifts left (too many products)

Q < K

Shifts right (too many reactants)

Q = K

Reaction at equilibrium

Remove product

Shift right

Remove reactant

Shift left

Add reactant

Shift right

Add product

Shift left

Increase pressure

Favors fewer gas moles

Decrease pressure

Favors more gas moles

Catalyst effect

No change to K or shift

Increase temp (endothermic)

Increases K

Increase temp (exothermic)

Decreases K

pH + pOH

14

Strong acid pH

-log[H+]

Strong base pOH

-log[OH-]

Weak acid equation

x = sqrt(Ka·C)

pKa formula

pKa = -log(Ka)

Half-equivalence point

pH = pKa

Weak acid + strong base equivalence

pH > 7

Strong acid + strong base equivalence

pH = 7

Henderson-Hasselbalch

pH = pKa + log(A-/HA)

Best buffer ratio

A-/HA ≈ 1

Conjugate base of HA

A-

Conjugate acid of B-

HB

ΔG formula

ΔG = ΔH - TΔS

ΔG° and K

ΔG° = -RT ln(K)

ΔG < 0

Spontaneous

ΔG > 0

Non-spontaneous

ΔG = 0

At equilibrium

ΔS > 0

Increased disorder

Always spontaneous

ΔH - and ΔS +

Never spontaneous

ΔH + and ΔS -

Spontaneous at high T

ΔH + and ΔS +

Spontaneous at low T

ΔH - and ΔS -

K > 1

ΔG° negative (products favored)

K < 1

ΔG° positive (reactants favored)

Oxidation

Loss of electrons (OIL)

Reduction

Gain of electrons (RIG)

Oxidizing agent

Gets reduced

Reducing agent

Gets oxidized

Oxidation occurs

At the anode

Reduction occurs

At the cathode

Electron flow

Anode → Cathode

Oxidation number of O

-2

Oxidation number of H

+1

Oxidation number of elements

0

MnO4- in acid

Mn2+

MnO4- in base

MnO42-

Acidic redox steps

Split → H2O → H+ → e- → combine

Basic redox steps

Do acidic then add OH- to kill H+

Initial pH weak acid

x = sqrt(Ka·C)

Before equivalence

Use Henderson-Hasselbalch

After equivalence

Use leftover strong base

acidic

pH less than 7

basic

pH greater than 7

amphoteric

a substance that can act as both an acid and a base

neutral

pH of 7

buffer

A solution that minimizes changes in pH when extraneous acids or bases are added to the solution.

entropy

a measure of the disorder of a system

A-

conjugate base

HA

acid

Ka = ….

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

proper chemical equation for the auto-ionization of water

2H2O(l) ⇌ H3O+(aq) + OH-(aq)

Kb = …

[BH+][OH-]/[B]

Kw = …

Ka x Kb = 1.0 x 10^-14

BH+

conjugate acid

B

base