Test 2-Ch. 18 Acid-Base Equilibria

Arrhenius acid-base definition
-acids and bases classified in terms of their formulas and their behavior in water
Arrhenius Acid
-a substance that has H in its formula and dissociates in water to yield H30+
Arrhenius Base
-a substance that has OH in its formula and dissociates in water to yield OH-
Arrhenius Neutralization
-occurs when the H+ ion from the acid and the OH- ion from the base combine to form H20
Acids and Bases as Electrolytes
-acids and bases are electrolytes in water, therefore, strong electrolytes (bases or acids) dissociate completely in water
Kc for Acids

-Kc is extremely large for strong acids

-Kc is very small for weak acids

Strong Acids

-HCl, HBr, HI, HClO4, HNO3,H2SO4


Stong Bases

-LiOH, NaOH, KOH, RbOH, CsOH, Sr(OH)2, Ba(OH)2

-Ca(OH)2 is NOT for class purposes

Strong Acid Types

-Hydrohalic Acids: HCl, HBr, HI

-Oxoacids in which the # of O atoms exceeds the # of ionizable protons by two or more

Weak Acids

-Hydrohalic Acid HF

-Acids in which H is not bonded to O or a halogen: e.g. HCN and H2S

-Oxoacids in which the # of O atoms equals or exceeds by one the number of ionizable protons

-Carboxylic Acids (formula-RCOOH)

Strong Bases

-M20 and MOH where M = Group 1A(1) metal

-MO or M(OH)2 where M = Group 2A(2) metal (besides Ca(OH)2)


Weak Bases

-electron-rich nitrogen atom are weak bases (and they are not Arrhenius bases)

-Ammonia (NH3)

-Amines (gen. formula RNH2, R2NH, or R3N)

Ion-product Constant for Water, Kw

Kw = [H30+][OH-] = 1.0E-14 (at 25 degrees C)

kw = kc[H20]^2

Consequences of the Auto-ionization of Water

-A change in [H30+] causes an inverse change in [OH-]

-Both ions are present in all aqueous systems

pH = -log[H30+]

pOH = -log[OH-]

Equilibrium Constants in pK

pK = -log[K]

-a low pK corresponds to a high K

pKw = pH + pOH = 14.00 at 25 degrees C
Bronsted-Lowry Acid Definition

-an acid is a proton donor, any species that donates an H+

-All Arrhenius Acids are Bronsted-Lowry acids

Bronsted-Lowry Base Definition

-A base is a proton acceptor, any species that accepts an H+ ion.

-Base must contain a lone pair of electrons to bind to H+ ion

The Bronsted-Lowry Acid-Base Perspective

-the only requirement for an acid-base reaction is that one species donates a proton and another species accepts it

-an acid-base reaction is a proton-transfer process

-a substance that acts as a base(accepts a H+) in one case and as an acid(donates a H+) in the other
Conjugate Acid-Base Pairs

-every acid has a conjugate base and vice-versa

-conjugate base has one fewer H and one more minus charge than the acid

-conjugate acid has one more H and one fewer minus charge than the base

Net Direction of Acid-Base Reaction

-a rxn proceeds to the greater extent in the direction in which a stronger acid and stronger base form a weaker acid and weaker base

-e.g. competition for the proton- stronger base wins and becomes conjugate acid

Why does a weaker acid has a stronger conjugate base?
-the acid gives up its proton less readily bc its conjugate base holds it more strongly

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