Chapter 17 (Exam 2) Flashcards
Acids (General Characteristics)
Sour taste, ability to dissolve many metals; ability to turn blue litmus paper red; neutralize bases
Common Acids
- Hydrochloric (HCl) - Sulfuric (H2SO4) - Nitric (HNO3O) - Acetic (HC2H3O2) - Citric (H3C6H5O7) - Carbonic (H2CO3) - Hydrofluoric (HF) - Phosphoric (H3PO4)
Carboxylic Acid
Contains: ((O)) H - O - C - R
Bases (General Characteristics)
Bitter taste, slippery feel (react to oils to form soap-like substance); turn red litmus paper blue; ability to neutralize acids
Alkaloids
Organic bases found in plants (often poisonous)
Common Bases
- Sodium Hydroxide (NaOH) - Potassium hydroxide (KOH) - Sodium bicarbonate (NaHCO3) - Sodium carbonate (Na2CO3) - Ammonia (NH3)
Arrhenius Definition: - Acid - Base - Acid + Base = ?
- Acid: Substance that produces H+ ions in aqueous solution –> H+ ions ALWAYS associate with H2O molecules to form hydronium ions (H3O+) –> Strong Acid: Completely ionizes in solution (weak: partially) - Bases: Substance that produces OH- ions in aqueous solution –> Strong Base: Completely dissociates in solution (weak: produces OH- by accepting proton from water/ionizing) - Acid + Base = Water
Bronsted-Lowry Definition: - Acid - Base
- Acid: Proton (H+) donor - Base: Proton (H+) acceptor - Acids + Bases always occur together
Amphoteric
Substances that can act as acids or bases
Conjugate Acid/Conjugate Base
- Any base to which a proton has been added - Any acid from which a proton has been removed NH3 (base) + H2O (acid) –> NH4+ (conj. acid) + OH- (conj. base) - Base accepts proton and becomes conjugate acid - Acid donates proton and becomes conjugate base
Binary Acids: Factors that Affect Ease of H+ Donated
- Factors influencing ease of H+ donated are polarity and strength - Increasing Electronegativity: Increasing Acidity Decreasing Strength: Increasing Acidity
Oxyacids
- Contain H bonded to O atom H - O - H - Y (branch off in diff. directions) - Influence acidity: Electron of Y (increasing electronegativity = weakening polarizing H-O bond–more acidic) - Number of O atoms bonded to Y: Draw electron density away from element Y (more = stronger acid)
Monoprotic Acid
Only one ionizable proton
Diprotic Acid
- Two ionizable protons
Strong Acids
- Hydrochloric (HCl) - Hydrobromic (HBr) - Hydroiodic (HI) - Nitric (HNO3) - Perchloric (HClO4) - Sulfuric (H2SO4) – Diprotic acid
Weak Acids
- Hydrofluoric (HF) - Acetic (HC2H3O2) - Formic (HCHO2) - Sulfurous (H2SO3) - Carbonic (H2CO3) - Phosphoric (H3PO4)
Generic Equilibrium Constant for Acid
HA (aq) + H2O –>/<– H3O+ + A-
HA (aq.) –>/<– H+ (aq) + A- (aq)
Ka = [H3O+][A-]/[HA]
Ka = [H+][A-]/[HA]
Water: Basicity and Acidity
- Water is amphoteric; when pure acts as an acid and a base itself
H2O + H2O –>/<–H3O+ + OH-
- Kw = [H+][OH-]
- Acidic: [H3O+] > [OH-]
- Basic: [OH-] < [H3O+]
- Kw = 1.0 x 10-14 at 25˚C
Calculating pH
- log[H3O+]
- [H3O+][OH-] = 1.0 x 10-14
(then use negative log of hydronium ions)
Finding [H3O+] and pH of Strong Acids
- Completely ionize, therefore concentration of H3O+ = concentration of the stron gacid
- Then -log(H3O+)
Finding [H3O+] and pH of Weak Acids
- Solve equilibrium problem
- Write out entirety of equation; solve ICE equilibrium problem
- Remember: HA (aq) + H2O (aq) –>/<– H3O+ (aq) + A- (aq)
- Use x is small approximation; check and make sure that percentage is []
Quadratic Equation
[- b +/- (b2 - 4ac)-2]/2a
from: ax2 + bx + c
Percent Ionization (Acids)
- Find concetration of hydronium ions
- Divide molarity of hydronium ions by initial molarity and multiply by 100%
Trends in Acids
- Equilibrium H3O+ concentration of weak acid increases with initial increasing concentration of acid
- Percent ionization of weak acid decreases with increasing concentration of acid
Mixtures of Acids: Strong and Weak
Finding pH and [H3O+]
- Relative strength of acids allows us to neglect weaker acid and focus on strong one
- Solve equilibrium for strong acid and the products of the reaction
Mixtures of Acids: Weak + Weak
Finding pH and [H3O+]
- 3 potential sources of hydronium (two weak acids and water)
- If Ka differs by factor of several 100s in magnitude, assume that weaker acid does not make contribution
- Solve equilibrium equation with largest Ka initial and the products
Common Strong Bases
- Lithium hydroxide (LiOH)
- Sodium hydroxide (NaOH)
- Potassium hydroxide (KOH)
- Strontium hydroxide [Sr(OH)2]
- Barium hydroxide [Ba(OH)2]
–> Mostly group 1A or 2A metal hydroxides
—> 1A: Highly soluble and can form concentrated base solutions
–> 2A: Slightly soluble (dissocate in one step)
Weak Bases/Common Weak Bases
- Produce OH- by accepting proton from H2O; ionize H2O to form OH-
- Carbonate ion (CO32-)
- Methylamine (CH3NH2)
- Ethylamine (C2H5NH2)
- Bicarbonate ion (HCO3-)
- Pyridine (C5H5N)
- Aniline (C6H5NH2)
–> All are either ammonia or amines
Weak Base Ionization Constant
- Kb: Extent of ionization of weak base; smaller the constant, weaker the base
Finding OH- of Strong Base Solutions
- Concentration of OH- equals concentration of initial reactant; take -log(H3O+) to find pH (again, Kw = 1.0 x 10-14)
Finding OH- and pH for Weak Base Solution
- Write out equation, solve for ICE equilibrium problem
- Use OH- x H3O+ = 1.0 x 10^-14 to find H3O+; then -log of hydronium!
Anions as Weak Bases
- View as conjugate base of an acid
- General: A- = conjugate base of HA
- Anion that is a conjugate base of weak acid is itself a weak base
- Anion that is conjugate base of strong acid is pH-neutral
- Cl- = HCl
- F- = HF
- NO3- = HNO3
- C2H3O2 = HC2H3O2
Kw = ?
Kw = Ka x Kb
pKa + pKb = 14
Cations as Weak Acids
- In some cases, act as weak acids
- Cations and counterions of strong bases typically pH neutral
- NH4+ (cation) = NH3 (base)
- C2H5NH3+ = C2H5NH2
Small, Highly Charged Cations
- Smaller, more highly chared cation is, the more acidic its behavior
Classifying Salt Solutions (4 Points)
1) Salts in which neither cation nor anion acts as and acid or base form pH-neutral solutions.
2) Salts in which cation does not act as an acid and anion acts as a base to form basic solutions.
3) Salts in which cation acts as an acid/anion does not act as a base forms acidic solutions.
4) Salts in which cation acts as an acid and anion acts as a base form solutions in which pH depends on relative strengths of acid/base
Polyprotic Acids
- Require more than one step to ionize
- Ka2 is always smaller for polyprotic acids (second proton must separate from an anion)
Concentrations of Anions for Weak Diprotic Acid Solution
(Concentration of X2-?)
- General polyprotic (H2X)
(1) H2X (aq) + H2O (l) –>/<– H3O+ (aq) + HX- (Ka1)
(2) HX- (aq) + H2O (l) –>/<– H3O+ (aq) + X2- (aq) (Ka2)
Concentration X2-: Use equlibrium constant and solve for X2-
Lewis Acids and Bases
- Lewis Acid
- Lewis Base
- Electron pair acceptor
- Electron pair donor
SUBSTANCE DOESN’T NEED TO CONTAIN H+ TO BE AN ACID
- Molecules with incomplete octets act as acids
- Some may reconfigure to act as Lewis Acids
- Cations may act as Lewis acids as well….ugh.
