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
pH = -log[H30+]
pOH

pOH = -log[OH-]

Equilibrium Constants in pK

pK = -log[K]

-a low pK corresponds to a high K

pKw
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

Amphiprotic
-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

Get access to
knowledge base

MOney Back
Guarantee
No Hidden
Charges
Unlimited
Knowledge base
Become a Member