Chapter 19.1 Teacher Notes
Vocabulary
conjugate acid- particle formed when a base gains a hydrogen ion
conjugate base-particle that remains when an acid has donated a hydrogen ion
conjugate pair- two substances related by the loss or gain of a single hydrogen ion.
hydronium ion- H3O+
amphoteric- substance that can act as both an acid and a base
monoprotic acids- acids that contain one ionizable hydrogen, ex. nitric acid, HNO3
diprotic acids- acids that contain two ionizable hydrogens, ex. sulfuric acid, H2SO4
triprotic acids- acids that contain three ionizable hydrogens, ex. phosphoric acid, H3PO4
Acids taste sour. Bases taste bitter and feel slippery.
Acid Base Theories
Arrhenius Acids- hydrogen containing compounds that ionize to yield hydrogen ions, H+, in aqueous solutions.
*Not all compounds that contain hydrogen are acids
Arrhenius Bases- compounds that ionize to yield hydroxide ions, OH-, in aqueous solutions.
NaOH(s) →Na+(aq) + OH-(aq)
Brønsted-Lowry Acids- a hydrogen ion donor
Brønsted-Lowry Bases- a hydrogen ion acceptor
*All Arrhenius acids and bases are Brønsted-Lowry acids and bases, however, not all Brønsted-Lowry acids and bases are Arrhenius acids and bases.
NH3(aq) + H2O(l) ↔ NH4+(aq) + OH-(aq)
base acid conj. acid conj. base
Lewis Acids- accepts a pair of electrons during a reaction to form a covalent bond
Lewis Base- donates a pair of electrons during a reaction to form a covalent bond
*Lewis was first scientist to discuss the significance of electron pairs in bonding
Hydrogen Ions and Acidity
Neutral solution- [ H+] and [OH-] are equal
In any aqueous solution, when [ H+] increases, [OH-] decreases, and when [OH-] increases, [ H+] decreases----Le Chatelier’s principle.
* Kw – ion-product constant for water=[ H+]x[OH-]=1.0x10-14
Acidic solution-[ H+] is greater than [OH-]
Basic solution-[ H+] is less than [OH-]; also known as alkaline solutions
Concept of pH
pH= - log[ H+]
*Proposed in 1909 by Danish scientist Soren Sorensen.
The pH scale ranges from 0, strongly acidic, to 14, strongly basic. Neutral solutions have a pH of 7.
pOH= - log [OH-]
pH + pOH = 14
Measuring pH
An indicator responds to pH changes over a specific range and changes color in response to acidic or basic conditions.