Key TermsAcidity - the level of acid in substances Arrhenius acid - a substance containing hydrogen that, when
dissolved in water, increases the concentration of H+ ionsArrhenius base - any substance that ionizes when it dissolves in
water to give the OH- ionBronsted-Lowry acid - proton donorBronsted-Lowry base - proton acceptor Conjugate acid - the compound formed when a base gains a
protonConjugate base - the compound formed when an acid loses a
protonHydrogen ion - a positively charged atom of hydrogenHydronium ion - the ion H3O+
Hydroxide ion - the OH- ion Ionization - the condition of being dissociated into ionsKw - is the constant for the self-ionization of water
Key TermsNeutralization reaction - a chemical reaction in which an acid and a
base interact with the formation of a saltpH - a figure expressing the acidity or alkalinity of a solution on a
logarithmic scalepH scale: 0-14pOH - the reciprocal of the logarithm of the hydroxide ion
concentrationSalt - a chemical compound formed from the reaction of an acid with
a baseStrong acid - an acid that ionizes completely in an aqueous solutionStrong base - a base that dissociates completely into a metal ion and
hydroxide ion in aqueous solutionWeak acid - an acid that dissociates incompletely Weak base - a chemical base that does not ionize fully in an aqueous
solution
SaltsIonic compounds that result from acid-base neutralization
Many, but not all, are soluble
Soluble salts dissociate in water and will conduct electricity
Soluble salts that conduct electricity in solution are electrolytes
Insoluble salts are non-electrolytes
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Nature of Acids and BasesThere are three broad categories of acids and
bases and the nature of each is defined by the category
Arrhenius – based on specific ions dissolved in water
Brǿnsted-Lowry – based on behavior associated with protons
Lewis (Not covered in this course)
Arrhenius AcidsCompounds that dissociate in water to produce
hydrogen ions (H+)
The hydrogen ions bond to the water molecules to form hydronium ions (H3O+)
Examples of Arrhenius acidsHClH2SO4
HNO3
HC2H3O2
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Arrhenius BasesCompounds that dissociate in water to
produce hydroxide ions (OH-)
Examples of Arrhenius basesNaOHKOH
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Properties of Acids & Bases Acids Bases
IonsDissociates to produce
H3O+ ionsDissociates to produce OH- ions
Taste Sour BitterFeel Not slippery SlipperypH < 7 > 7Electrical Conductivity Conducts current Conducts current
Reactivity with metalsReacts with active
metals to produce H2 (g)
Does not react with metals
Color with Litmus indicator
Red Blue
Color with phenolphthaleinindicator
Clear Pink
Brǿnsted-Lowry AcidMore broad definition of acid
Includes any substance that reacts in a particular reaction to produce protons (H+) – proton donor
Includes Arrhenius Acids
Brǿnsted-Lowry BaseMore broad definition of base
Also include any substance that reacts in a particular reaction to accept protons (H+) – proton acceptor
Includes Arrhenius Bases
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Brǿnsted-Lowry Acid-Base Reaction NH3 + H2O ↔ NH4
+ + OH- (Base) (Acid) (Conjugate Acid) (Conjugate Base)
The water donates a H+ to the ammonia and is therefore the acid
The ammonia accepts the H+ from the water and is therefore the base
These reactions are reversible and the ammonium is consider the conjugate acid as it will be the donor (acid) in the reverse direction
Likewise the hydroxide will be the acceptor (base) in the reverse reaction and is the conjugate base
Naming Arrhenius Acids & BasesArrhenius Bases follow the naming rules for ionic
compounds. All of these are hydroxide compounds using different metal ions.
Arrhenius Acids are named using a new set of rules as these are all unusual covalent compounds that dissociate in water
Rules for Binary Acids – acids with only two elements
Rules for Ternary Acids – acids with polyatomic ions
Naming Binary Arrhenius AcidsArrhenius Acids involving only two types of
atoms have the prefix “hydro” and the suffix “ic”.
H2S has only hydrogen atoms and sulfur atoms
Hydro-sulfur-ic → Hydrosulfuric Acid
HBr has only hydrogen atoms and bromine atoms
Hydro-bromine-ic → Hydrobromic Acid
Naming Ternary Arrhenius Acids Arrhenius Acids involving a polyatomic ion are named according
to the polyatomic ion as follows:
When an ion ending in “ate” is present with no “per” prefix , the acids are named after the non-oxygen atom and uses the suffix “ic” H3PO4 has a phosphate polyatomic ion
Phosphor-ic Phosphoric Acid
When an ion ending in “ite” is present with no “hypo” prefix, the acids are named after the non-oxygen atom and uses the suffix “ous” HClO2 has a chlorite polyatomic ion chlor-ous Chlorous Acid
When an ion ending in “ate” is present with “per” prefix , the acids are named after the non-oxygen atom with “per” as the prefix and the suffix “ic”
Ions ending in “ite” with “hypo” prefix are named after the non-oxygen atom with “hypo” prefix and the suffix “ous”
Anion prefix
Anion suffix
Acid prefix Acid suffix Example
per ate per ic acid perchloric acid (HClO41-)
ate ic acid chloric acid (HClO31-)
ite ous acid chlorous acid (HClO21-)
hypo ite hypo ous acid hypochlorous acid (HClO1-)
ide hydro ic acid Hydrochloric acid (HCl)
Auto-Ionization of Water - KwWater partially auto-ionizes to form an equal number of
hydrogen ions and hydroxide ions
Kw is the numerical value associated with process and is referred to as the equilibrium constant for water and is the basis of the pH scale
Kw = (concentration of H+) (concentration of OH+) = (1 x 10-7) (1 x 10-7)
Kw = [H+] [OH+] = 1 x 10-14
This constant means that for any solution, if the hydrogen ion concentration or hydroxide ion concentration is known it is simple to calculate the other.
pHMeasures the acidity and basicity of a
solution
Represents the relative concentration of hydrogen and hydroxide ions
Used to simplify discussions concerning the amount of acid or base in the solution
Uses a logarithmic scale
Image used courtesy of: http://en.wikipedia.org/wiki/PH
pH ScaleRanges from zero to 14
<7 = acid (more hydrogen ions than in water)>7 = base (less hydrogen ions than in water)7 = neutral (same concentration of hydrogen ions
as in water)
The concentration of both ions in water is 10-7 M which corresponds to a pH of 7 - neutral
A difference in pH corresponds to a difference in concentration of a factor by a factor of 10 difference in pH of 1 corresponds to a difference in
concentration of a factor of 101 or 10 difference in pH of 2 corresponds to a difference in
concentration of a factor of 102 or 100 difference in pH of 3 corresponds to a difference in
concentration of a factor of 103 or 1000
pH CalculationpH = - log [H+] [H+] = 10-pH
Since the equation for calculating pH has a negative sign, a low pH corresponds to a higher concentration
pOH = - log [OH-] [OH-] = 10-pOH
pH + pOH = 14 - log 10-7 M + -log 10-7 M = 14 Water 7 + 7 = 14
pH IndicatorspH indicators are made using weak acids or
bases
All pH indicators have a characteristic color change based on the pH of a solution
Different pH indicators are useful in different portions of the pH scale Some indicators like litmus can distinguish
solutions as acid or baseOthers are used to determine how acidic or
how basic a solution is
Strong Acids & Weak AcidsStrong Bases & Weak BasesStrong Acids and Strong Bases completely, or
nearly completely, ionize in water making them excellent conductors of electricity
Acids – Hydrochloric, sulfuric, nitric Bases – Sodium hydroxide, potassium hydroxide
Weak Acids and Weak Bases only partially ionize in water making them poor conductors of electricity
Acids – Acetic, phosphoric, carbonic Bases – Ammonia, baking soda
Neutralization ReactionsReactions between strong Arrhenius acids and strong Arrhenius
bases
The products are water and a salt. The water forms from the hydrogen and hydroxide ions present. The salt is formed from the remaining ions of the acid and base.
The degree of neutralization is dependent on the amount and concentration of the acid and base
If the amounts and concentrations result in an equal number of moles of both, the resulting solution is neutral.
If the salt formed is insoluble, it will settle to the bottom as a precipitate.
If the salt is soluble, it will remain in a diluted solution.
Differentiating Reaction CategoriesReduction-Oxidation
Combustion reactions Synthesis reactions involving an element reactant Decomposition reactions producing an element product Single-Replacement reactions
Precipitation Single-Replacement reactions involving metal elements Double-Replacement reactions forming an insoluble
product Acid-Base Neutralization reactions forming an
insoluble salt
Acid-Base Neutralization of Strong Acids & Bases Reactions involving strong Arrhenius acids and bases forming water
and a salt
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