Acids & Bases

A. Properties ACIDS BASES electrolytes  electrolytes sour taste bitter taste turn litmus red turn litmus blue react with metals to form H2 gas slippery feel vinegar, milk, soda, apples, citrus fruits ammonia, lye, antacid, baking soda ChemASAP

Arrhenius acids & bases Arrhenius - In aqueous solution… Acids form hydronium ions (H3O+) Hydrogen ions (protons) plus water HCl + H2O  H3O+ + Cl– H Cl O – + acid

Strong vs. Weak

Increasing polarity = increasing strength

Organic acids Acids that contain the carboxyl group -COOH Weak acids Acetic acid – CH3COOH See your notes for other examples

pouvoir hydrogène (Fr.) pH Scale 14 7 INCREASING ACIDITY INCREASING BASICITY NEUTRAL pH = -log[H3O+] pouvoir hydrogène (Fr.) “hydrogen power”

pH of Common Substances B. pH Scale pH of Common Substances

NH3 + H2O  NH4+ + OH- B. Definitions – + Arrhenius - In aqueous solution… Bases form hydroxide ions (OH-) NH3 + H2O  NH4+ + OH- H N O – + base

Alkalinity Alkaline: solution in which a base has completely dissociated in water to yield aqueous OH- ions Alkalinity depends on concentration of OH- in solution

Strong vs. Weak Bases Strong base Weak base Strong electrolytes – complete dissociation Weak base Removes H+ from water leaving OH-behind

-Substances that already contain ions (i.e. ionic compounds) merely release their ions as the crystal dissociates. -Substances that are neutral molecules (i.e. molecular/covalent compounds) must react with water to produce ions (called ionization) -CONCENTRATED/DILUTE – tell how much acid or base is dissolved in solution (molarity, molality, %conc.) -STRONG/WEAK – refer to the extent of ionization or dissociation of an acid or base

Arrhenius Theory Had some inadequacies: Requires that substances be aqueous NH3, Na2CO3, and C6H5NH2 (aniline) are all basic but they are NOT hydroxides So his theory had to be expanded (added on to)

Bronsted Lowry Includes all Arrhenius acids and bases Plus substances that are not in aqueous solutions and do not have hydroxide

HCl + H2O  Cl– + H3O+ Bronsted Lowry acid conjugate base base Brønsted-Lowry Acids are proton (H+) donors. Bases are proton (H+) acceptors. HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

Proton Transfer Reaction H2O + HNO3  H3O+ + NO3– B A CA CB

Acids – turn to page 465-466 for examples Monoprotic Polyprotic Diprotic Triprotic

Just a note The terms ACID & BASE are used for reactants The terms CONJUGATE ACID & CONJUGATE BASE are used for products Reactants must be stronger than the products in order for the reaction to proceed/occur with any significant extent

Conjugate acid/base Conjugate base – remains after B-L acid has given up proton Conjugate acid – remains after B-L base has accepted proton Conjugate pair – differ from each other by the loss or gain of 1 H+ ion

Strength Strong acids have weak conjugate bases and vice versa The larger the Ka/Kb value – the stronger the acid or base (see chart) Reactions always proceed from the strong to the weak. Strong acid/base ionize readily, the conjugates must be too weak to compete

Strength

C. Strength Strong Acid/Base 100% ionized in water strong electrolyte - + HCl HNO3 H2SO4 HBr HI HClO4 NaOH KOH Ca(OH)2 Ba(OH)2

C. Strength Weak Acid/Base does not ionize completely weak electrolyte - + HF CH3COOH H3PO4 H2CO3 HCN NH3

Amphoteric - can be an acid or a base. B. Definitions NH3 + H2O  NH4+ + OH- B A CA CB Amphoteric - can be an acid or a base.

B. Definitions HF H3PO4 H3O+ F - H2PO4- H2O Give the conjugate base for each of the following: HF H3PO4 H3O+ F - H2PO4- H2O

B. Definitions Br - HSO4- CO32- HBr H2SO4 HCO3- Give the conjugate acid for each of the following: Br - HSO4- CO32- HBr H2SO4 HCO3-

Lewis Acid Base Theory Arrhenius theory & Bronsted-Lowry theory still did not cover all the substances that were acidic & basic SO there must be more Lewis based his theory on Bonding Structure

Lewis Acids & Bases Lewis base Lewis acid Acids are electron pair acceptors. Bases are electron pair donors. Draw the example Lewis base Lewis acid

Lewis Acids & Bases Lewis acids = e- pair acceptor Lewis base = e- pair donor Lewis reaction = the formation of one or more covalent bonds between an electron pair donor and an electron pair acceptor

Neutralization Reaction of hydronium and hydroxide ions to form water molecules and another compound Salt – an ionic compound composed of cation from the base and anion from an acid ACID + BASE>SALT + WATER

Acid Rain Acid Rain – any precipitation that has an unusually high concentration of sulfuric or nitric acids, resulting from chemical pollution of the air Unpolluted rain has a pH of 5.6 Acid rain = pH of 4.6 (10 times more acidic)

Acid Rain Can dissolve marble buildings and statues Kills plankton and other aquatic animals Dissolves metals and nutrients in the soil Usually caused by sulfur trioxide and nitrogen oxide when they combine with water

Mole Ratios Use the coefficients in the balanced equations as ratios to do your calculations