Key Terms Acidity - the level of acid in substances Arrhenius acid - a substance containing hydrogen that, when dissolved in water, increases the concentration of H + ions Arrhenius base - any substance that ionizes when it dissolves in water to give the OH - ion Bronsted-Lowry acid - proton donor Bronsted-Lowry base - proton acceptor Conjugate acid - the compound formed when a base gains a proton Conjugate base - the compound formed when an acid loses a proton Hydrogen ion - a positively charged atom of hydrogen Hydronium ion - the ion H 3 O + Hydroxide ion - the OH - ion Ionization - the condition of being dissociated into ions Kw - is the constant for the self-ionization of water

Key Terms Neutralization reaction - a chemical reaction in which an acid and a base interact with the formation of a salt pH - a figure expressing the acidity or alkalinity of a solution on a logarithmic scale pH scale: 0-14 pOH - the reciprocal of the logarithm of the hydroxide ion concentration Salt - a chemical compound formed from the reaction of an acid with a base Strong acid - an acid that ionizes completely in an aqueous solution Strong base - a base that dissociates completely into a metal ion and hydroxide ion in aqueous solution Weak acid - an acid that dissociates incompletely Weak base - a chemical base that does not ionize fully in an aqueous solution

Salts Ionic 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 Image used courtesy of:

Nature of Acids and Bases There 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 Acids Compounds that dissociate in water to produce hydrogen ions (H + ) The hydrogen ions bond to the water molecules to form hydronium ions (H 3 O + ) Examples of Arrhenius acids HCl H 2 SO 4 HNO 3 HC 2 H 3 O 2 Image used courtesy of: chemistry/arrhenius-theory.html

Arrhenius Bases Compounds that dissociate in water to produce hydroxide ions (OH - ) Examples of Arrhenius bases NaOH KOH Image used courtesy of: 101Fall/CHM101LectureNotes htm

Properties of Acids & Bases AcidsBases Ions Dissociates to produce H 3 O + ions Dissociates to produce OH - ions TasteSourBitter FeelNot slipperySlippery pH< 7> 7 Electrical ConductivityConducts current Reactivity with metals Reacts with active metals to produce H 2 (g) Does not react with metals Color with Litmus indicator RedBlue Color with phenolphthalein indicator ClearPink

Brǿnsted-Lowry Acid More broad definition of acid Includes any substance that reacts in a particular reaction to produce protons (H + ) – proton donor Includes Arrhenius Acids

Brǿnsted-Lowry Base More broad definition of base Also include any substance that reacts in a particular reaction to accept protons (H + ) – proton acceptor Includes Arrhenius Bases Image used courtesy of:

Brǿnsted-Lowry Acid-Base Reaction NH 3 + H 2 O ↔ NH 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 & Bases Arrhenius 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 Acids Arrhenius Acids involving only two types of atoms have the prefix “hydro” and the suffix “ic”. H 2 S 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” H 3 PO 4 has a phosphate polyatomic ion Phosphor-icPhosphoric 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-ousChlorous 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 prefixAnion suffixAcid prefixAcid suffixExample perateperic acidperchloric acid (HClO4 1- ) ateic acidchloric acid (HClO3 1- ) iteous acidchlorous acid (HClO2 1- ) hypoitehypoous acidhypochlorous acid (HClO 1- ) idehydroic acidHydrochloric acid (HCl)

Auto-Ionization of Water - K w Water partially auto-ionizes to form an equal number of hydrogen ions and hydroxide ions K w 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 K w = (concentration of H + ) (concentration of OH + ) = (1 x ) (1 x ) K w = [H + ] [OH + ] = 1 x 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.

pH Measures 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:

pH Scale Ranges 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 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 10 1 or 10 difference in pH of 2 corresponds to a difference in concentration of a factor of 10 2 or 100 difference in pH of 3 corresponds to a difference in concentration of a factor of 10 3 or 1000

pH Calculation pH = - 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 M + -log M = 14 Water = 14

pH Indicators pH 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 base Others are used to determine how acidic or how basic a solution is

pH Indicator Ranges & Colors

Strong Acids & Weak Acids Strong Bases & Weak Bases Strong 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 Reactions Reactions 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.

Neutralization Reactions Image used courtesy of:

Differentiating Reaction Categories Reduction-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 Image used courtesy of: itationreactio