Chem II exam II

Strong Acids

HCl

HBr

HI

H₂SO₄ (polyprotic acid)

HNO₃

HClO₄

HClO₄(oxoacid)

HClO₃^* (sometimes) also oxoacid

note: 100% dissociation

Strong Bases

LiOH

NaOH

KOH

RbOH

CsOH
Ca(OH)2

Sr(OH)2

Ba(OH)2

note: 100% dissociation

Oxoacid

3 elements: hydrogen and oxygen bonded, and another element

• 1) more oxygen = more acidic

• 2) more electronegative atom = more acidic

Binary Acids

typically composed of exactly two elements (Hydrogen + another)

notes:

• the stronger an acid, the weaker its conjugate base

• the stronger a base, the weaker its conjugate acid

Conjugate Base

To find a conjugate base, remove one proton (H+) from the acid’s chemical formula and decrease it’s net charge by 1

examples: Acid → conjugate base

• HCl → Cl^-

• HCO₃^- → CO₃^2-

Conjugate Acid

To find a conjugate acid, add one proton (H+) to the base’s formula and increase its net charge by +1

example: Base → Conjugate Acid

• NH₃ → NH₄⁺

• OH^- → H₂O

Polyprotic acids

An acid that can act as a proton donor more than once

• as they donate H+, it becomes harder to donate successively (becomes less acidic along the way)

• The intitial substance will be the most abundant for a weak acid

  • reminder, H₂SO₄, a strong acid will have zero because 100% dissociation

Lewis Acids

Electron Acceptors

CATIONS (+)

Negligible acids: conjugate acids of strong bases. (any acid outside of these will be considered an acid)

• Group 1 & 2: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Sr²⁺, Ba²⁺

• Transition Metals (+1)

note: HSO₄^- is an anion, however it is ACIDIC because it is polyprotic acid

Lewis Base

Electron Donors

ANIONS (-)

Negligible: conjugate bases of strong acids. (any base outside of these will be considered a base)

• Cl^-, Br^-, I^-, NO₃^-, ClO₄^-, ClO₃^-

Kb

The equilibrium constant specifically for when a WEAK BASE dissociates

Kb= [OH-] [HA] / [A-]

[OH-]= √(kb * [A-]i)

• this is a shortcut for when <5%

The smaller the value of Kb, the weaker base

The greater the value of Kb, the stronger the base

Ka

The equilibrium constant specifically for when a WEAK ACID dissociates

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

[H+]= √(ka * [HA]i)

• this is a shortcut for when <5%

Ka=10^-pKa

The smaller the value of Ka, the weaker the acid

The greater the value of Ka, the stronger the acid

Water Ionization

water can act as a base or acid

H₂O → H+ + OH-

In pure water: Kw= [H+] [OH-]

• at 25 degrees celsius, Kw=1×10^-14

• Kw= Ka * Kb = [H+] [OH-]

pH

the logarithmuc scale to measure how acidic (basic)

pH= -log(H+) H+ = 10^-pH

pOH= -log(OH-) OH- = 10^-pOH

pH+pOH = 14