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Unit 16 - Acid-Base Equilibria, image - Coggle Diagram
Unit 16 - Acid-Base Equilibria
16.1 - 16.2 Definitions of Acids and Bases
Bronsted-Lowry acid - proton (H+) donor
Bronsted Lowry base - proton (H+) acceptor
Every acid has a conjugate base, formed by removing the proton from the acid.
Every base has a conjugate acid, formed by adding a proton to the base.
Strong acids completely dissociate in water. (→)
Weak acids only partly dissociate in water. (⇋)
16.3 The Autoionization of Water
Water is called amphoteric because it can react as an acid or a base.
autoionization
ion-product constant for water, KW. At 25oC, KW = 1.0 x 10-14
16.4 The pH Scale
pH = -log[H+]
Kw = [H3O+][OH-] = 1.0 x 10-14
[H3O+] = [OH-] = 1.0 x 10-7M
pOH = -log[OH-]
pKw = -log Kw
pH + pOH = 14 = pKw
16.5 Strong Acids and Bases
Strong Acids
Monoprotic strong acids:
HCl Hydrochloric acid
HBr Hydrobromic acid
HI Hydroiodic acid
HNO3 Nitric acid
HClO3 Chloric acid
HClO4 Perchloric acid
Diprotic strong acid:
H2SO4 Sulfuric acid
[H3O+] = [acid]
Strong Bases
LiOH (lithium hydroxide)
NaOH (sodium hydroxide)
KOH (potassium hydroxide)
Ca(OH)2 (calcium hydroxide)
RbOH (rubidium hydroxide)
Sr(OH)2 (strontium hydroxide)
CsOH (cesium hydroxide)
Ba(OH)2 (barium hydroxide)
16.6 Weak Acids
Ka = [H+][A-]/[HA]
Percent Ionization
Percent ionization = Ionized / Original * 100%
Percent Ionized = [H+]eq/ [HA]initial * 100
16.7 Weak Bases
Kb = [OH-][HB]/[B-]
Weak Bases :
nonbonding pair of electrons, ready to serve as a proton acceptor.
Anions of weak acids (conjugate bases of weak acids after they have lost a proton).
16.8 Relationship Between Ka and Kb
Ka x Kb = Kw
(Kw = 1.0 x 10-14)
pKa = -logKa and pKb = -logKb
pKa + pKb = pKw = 14.00
16.9 Acid-Base Properties of Salt Solutions
Hydrolysis (meaning water splitting) occurs when these ions react with water to generate H+ or OH-.
Anions, negative ions of salts, can react with water in a hydrolysis reaction to form OH- and the conjugate acid and will raise the pH of a solution:
Cations, with acidic protons (like NH4+) and metal cations, will react with water to lower the pH of a solution.
Effects on solution
1.An anion that is the conjugate base of a strong acid will not affect the pH. (ex. Br-)
2.An anion that is the conjugate base of a weak acid will increase the pH. (ex. CN-)
3.A cation that is the conjugate acid of a weak base will decrease the pH.
4.Cations of the strong Arrhenius bases will not affect the pH.
5.Other metal ions will cause a decrease in pH.
16.10 Acid-Base Behavior and Chemical Structure
Factors Affecting Acid Strength
Polarity must be present and the Hydrogen must be the less electronegative element in the bonds
Thus, because polarity increases going from left to right on the periodic table, acidity decreases as you move to the right in a period.
Very strong bonds are less easily dissociated than weaker ones.
Therefore, though HF has a tremendous amount of polarity, its strong bond strength (and ability to form H bonds) limits its ability to dissociate and subsequent acid strength compared to other strong acids in Group 17.
Therefore, acid strength increases going down a group.
Oxyacids
Oxyacids contain one or more O-H bonds. Oxyacids (ex. H2SO4) bound to a central atom
Generally, as the electronegativity of the central atom increases, the acidity increases
For a series of oxyacids (with the same central atom), acidity increases with the number of oxygens present. The acidity increases with the oxidation number of the central atom.
