acids and bases Flashcards
State the arrhenius definition
Acids produce hydrogen ions in aq solutions and bases produce hydroxide ions in aq solutions
State the bronsted-lowry definition
An acid is a proton donor and a base is a proton acceptor
According to the bronsted-lowry definition what are acidic protons often attached to
Oxygen
Halogens
Nitrogen atoms
According to the bronsted-lowry definition what do bases need
Lone pair electrons to act as a proton acceptor
Acids and bases occur as what
Acid-base pairs
Base –> conjugate acid
Acid –> conjugate base
What is ka
Acidity constant
Ka = [H+][A-]/[HA]
Describe strong acids
Most of acid is dissociated (ionized, strong electrolyte) Ka = large Equilibrium lies far right [H+]=[HA]initial A- much weaker base than H20
State strong acids
HCl HI HBR HNO3 H2SO4 HClO4
Describe weak acids
Ka = small
Equilibrium lies far left
[H+] < [HA]initial
A- much stronger base than a H2O
State weak acids
HF
CH3COOH (acetic acid)
HCOOH (formic acid)
HOOCCH2CCH2COOHCOOHOH (citric acid)
Describe relationship between acid and base conjugate pairs
Inverse relationship
Strong acid –> doesn’t react as base (spectator)
Weak acid –> weak base
Doesn’t react as acid –> strong base
What is water
Amphoteric
Acts as an acid or base
What is Kw
Ion product constant of water
Kw=[H3O+][HO-] = 1.0x10^-14 @ 25degrees c
What is Kw in neutral
[H30+]=[HO-] = x
Kw=x^2 –> x=1.0x10^-7
What is Kw in acidic
[H30+]>[OH-]
What is Kw in basic
[H30+] IS LESS THAN [OH-]
State relationship between H+ and pH
As [H+] increases pH decreases
As [H+] decreases or [HO-] increases pH increases
State formulas for the pH scale
Kw=[H3O+][HO-] = 1.0x10^-14 pH = -log [H+] pOH = -log [HO-] -logKw = -log [H+]-log[HO-] = 1.0x10^-14 Pkw = pH + pOH / pH+pOH = 14.00 [H+]= 10^-pH [pOH] = 10^-pOH *2 decimal places, 2 sig figs*
State what percent dissociation is and the formula
Extent of ionization for a weak acid
%diss= (molarity of H+ at equil / initial concentration) x 100
How is percent dissociation affected as weak acid becomes more dilute
Increases
Formulas for pka, ka, kb and pkb
- logpka=pka pka goes down ka goes up
- logpkb=pkb pkb goes down kb goes up
State formula for Kb
Kb = [BH+][OH-]/[B]
State strong bases
LiOH KOH NaOH RbOH CsOH Mg(OH)2 Ca(OH)2 Ba(OH)2 Sr(OH)2
State weak bases
Amines = ammonia, methylamine, ethylamine, aniline and pyridine
Hydroxylamines
What are polyprotic acids
Molecules that have more than one acidic proton
What is special about polyprotic acids
Product of 1st reaction = reactant of 2nd reaction
Each dissociation step has a Ka associated with it
How to solve weak polyprotic acids
Must do 2 ice tables and carry down [H+] from first table
How do we deal with something - x in acid base chemistry
Use 5% rule, approximation
If doesn’t work then use quadratic formula
State the generalizations about WEAK polyprotic acids
All of [H+] comes from first dissociation step
Very little of HA- dissociates, assume [H+]=[HA-]
Concentration of [A2-]=ka2
How to solve strong polyprotic acids
Don’t need ka1 –> first dissociation (first ice table) goes to completion
Concentration of H+ carries down to the second ice table
What are salts
Ionic compounds that are products of acid-base neutralizations
Which salts do not affect pH
Salts of the cations of strong bases
Salts of the anions of strong acids
Which salt produces basic solutions
Salts containing cation (with neutral properties) and an anion that is the conjugate base of a weak acid
Which salt produces acidic solutions
Salts containing anion (with neutral properties) and a cation that is the conjugate acid of a weak base
State the relationship for any conjugate acid base pair
Inverse relationship between ka of acid and kb of base
Ka x Kb = Kw
PKa + PKb = 14.00
What do highly charged metal ions form
Complex ions and produce acidic solutions
What happens when both ions in a salt have acid-base properties
Competition between K’s
Ka>Kb pH < 7 acidic
Ka=Kb pH = 7 neutral
Ka is less than Kb ph is less than 7 = basic
What are covalent oxides
They produce acidic solutions
SO3, SO2, CO2, NO2, etc
What are ionic oxides
They produce basic solutions
CaO, K2O, etc
What is the relationship between acidity and increasing electronegativity
Proportional
Acidity increases when going down a column in periodic table
Describe hydrogen halides
Weak acid = strong bond
Strong acid = weak bond
Describe oxyacids
Electron withdrawing effect (inductive) of electronegative atoms makes the O-H bond more acidic
State lewis model definition
Lewis acid is an electron pair acceptor and a lewis base is an electron pair donor (Includes bronsted lowry acids and bases)
Lewis base = e- pair donor
Lewis acid = e- pair acceptor
Acid-base properties of salts: neutral salts
Cation is neutral (alkali metal or alkaline earth metal)
Anion is conjugate base of a strong acid
Ex = NaCl, KNO3
Acid-base properties of salts: basic salts
Cation is neutral (alkali metal or alkaline earth metal)
Anion is conjugate base of a weak acid
Ex = CH3COOHNa, NaCN
Acid-base properties of salts: acidic salts
Cation is conjugate acid of a weak base (or highly charges metal cation)
Anion is the conjugate base of a strong acid
Ex = NH4Cl, AlCl3
