Chem 1212 Ch 15

Arrhenius Definition: Acid

Substance w/ an H in its formula that can dissociate in H?O to give H?O?
-HCl, CH?COOH, HCN
-NOT CH? (doesn't meet criteria)

Arrhenius Definition: Base

Substance w/ OH in its formula that can dissociate in H?O to give OH?
-NaOH, Ca(OH)?
-NOT CH?CH?OH (Alcohol's are not basic)

Bronsted-Lower Acid-Base Definition

in View of Proton (H?)
Acid: H? donor
Base: H? acceptor (OH? is generated by abstracting H? from H?O)
-Does not require acid to take place in water

Arrhenius and Bronsted-Lowery

-All Arrhenius acids are B-L acids
-All B-L Bases are not Arrhenius bases but all Areehnius bases contail the B-L base, OH?
-H? Goes to stronger Base

Water is atphoteric

H?O is atphoteric, it can act as an acid or base.

Autoionization of Water (Kw)

Kw=autoionization constant
Kw=[H?O?][OH?]
Kw=1.0x10?�? (at 25�C)

Relation of pH and Concentration

pH=-log??[H?O?]
[H?O?]=10^(-pH)

Relation of pH and pOH

pH+pOH=14.00
pKw=pH+pOH

Basic or Acidic

pH>7 is Basic
pH<7 is Acedic

monoprotic and diprotic acid

Monoprotic acid: HA
Diprotic acid: H?A

Strong Acids

-HCL, HBr, HI, H?SO?, HNO?, HCLO?
-Other oxoacids where # O exceeds # of ionizable H by 2 or more
-ex. H?SeO?
-All other are weak acids

Strong Bases

-Li?O, LiOH, CaO, Ca(OH)? are examples
-Soluble oxides/hydroxides of Group 1 ions and Ca�?, Sr�? and Ba�? from Group 2
-Be and Mg oxides/hydroxides are not very soluble in H?O so are not considered strong
-All other are weak Bases

Stong/Weak Acid/Base Term

-"Strong" refers to degree of dissociation and not to the reactivity of the acid/base.
-Strong Acids/Bases dissociate completely and weak acids/bases do not

Acid-Dissociation Constant Ka

HA(aq)+H?O(l)?H?O?(aq)+A?(aq)
Ka=[H?O?][A?]/[HA]

Base-Dissociation Constant Kb

B(aq)+H?O(l)?BH?+OH?(aq)
Kb=[BH?][OH?]/[B]

Relative strength of Acid/Base

equation with ? (completion) is stronger than equation with ? (equilibrium)
Ka bigger means stronger acid
Kb bigger means base is stronger

Strength of conjugate acid/base pairs

-strong acids have very weak conjugate bases
-strong bases have very weak conjugate acids
-weak acids have weak conjugate bases
-weak bases have weak conjugate acids

Predominate direction of reaction

Strength determines direction (? or ?) of reation.
Mixture of acids and bases predominates strong?weak

Fraction ionized

fraction ionized=(x/initial moles)�100%
-note that "x" is from ICE table

Polyprotic acids

Acids w/ more than 1 ionizable proton.
only use first Ka others are not significant

Relationship between Ka and Kb

Ka�Kb=Kw
pKa+pKb=pKw

pH of Salt Solutions

If salts are formed from the cations of weak bases and/or the anions of weak acids, the pH of the resulting solutions are not neutral

Molecular Properties of Acid Strength: Hydrides

Hydrides-Element w/ Hydrogen
-as central nonmetal becomes larger (down a group), bond strength decreases and acid strength increases
-as electronegativity of central nonmetal increases, acid strength increases (right on periodic table)

Molecular Properties of Acid Strength: Oxoacids

Oxoacids-Acid with Oxygen
-Acid strength increases w/ the # of oxygen atoms when central nonmetal remains the same
-If there are the same number of oxygen atoms, the acid strength increases w/ the electronegativity of the central nonmetal.

Lewis Acid-Base Definition

Front the POV of electron pairs
Acid: e? pair acceptor
-e? deficient, BF?, metal cations (Mg�?)
Base: e? pair donor
-lone pair e?, NH? works here too
Adduct: single species that contains a new covalent bond
Any metal ion acts as a Lewis acid with dissolve

Nitrogen Bases

Neutral or negative charged compounds containing Nitrogen are Bases ex NH?, CH3CH2NH2
Positively charged Nitrogen compounds are Acids ex NH??, CH3CH2NH3?