Acids and Bases

Acid Properties Sour taste (citrus fruits) Sour taste (citrus fruits) Conduct electric current Conduct electric current Change the color of indicators Change the color of indicators React with bases to produce salt and water: HCl + NaOH  H 2 O + NaCl React with bases to produce salt and water: HCl + NaOH  H 2 O + NaCl Some react with metals to release H 2 gas: Some react with metals to release H 2 gas: Mg + 2HCl  MgCl 2 + H 2

Naming Acids Review Binary Acids: Binary Acids: –Hydroiodic Acid HI HI –HF Hydrofluoric Acid Hydrofluoric Acid Ternary Acids (oxyacids) HClO 4 Perchloric Acid HClO 3 Chloric Acid HClO 2 Chlorous Acid HClO Hypochlorius Acid

Base Properties Bitter taste (coffee) Bitter taste (coffee) Feel slippery (soap) Feel slippery (soap) Change the color of indicators Change the color of indicators Caustic- attack the skin, cause severe burns Caustic- attack the skin, cause severe burns Conduct electric current Conduct electric current

Arrhenius Acids and Bases Arrhenius Acid: Arrhenius Acid: A compound that produces H + in solution. A compound that produces H + in solution. Ex: HCl (g) + H 2 O  H 3 O + (aq) + Cl - (aq) Ex: HCl (g) + H 2 O  H 3 O + (aq) + Cl - (aq) Arrhenius Base: Arrhenius Base: A compound that produces OH - in solution. A compound that produces OH - in solution. Ex: NaOH (s)  Na + (aq) + OH - (aq) Ex: NaOH (s)  Na + (aq) + OH - (aq) H2OH2O

Acid/Base Strength Strong Acid: Ionizes completely in aq. soln. Strong Acid: Ionizes completely in aq. soln. HClH 2 SO 4 HBrHNO 3 HIHClO 4 Strong Bases: Group 1 and 2 hydroxides

Acid-Base Theories Bronsted-Lowry: expands Arrhenius definition of acids and bases. Bronsted-Lowry: expands Arrhenius definition of acids and bases. –Bronsted-Lowry Acid: proton donor –Bronsted-Lowry Base: proton acceptor ex: HCl + NH 3  NH Cl - ex: HCl + NH 3  NH Cl - Monoprotic B-L Acid B-L Base ex2: H 3 PO 4 + H 2 O  H 3 O + + H 2 PO 4 - Which is the B-L Acid? B-L Base?

Lewis Acids and Bases Based on bonding and structure and include substances that may not include Hydrogen. Based on bonding and structure and include substances that may not include Hydrogen. –Lewis Acid: electron pair acceptor –Lewis Base: electron pair donor ex: BF 3 (aq) + F - (aq)  BF 4 - (aq) ex: BF 3 (aq) + F - (aq)  BF 4 - (aq) Draw the dot structure for these substances and classify as a Lewis Acid or Base. Lewis Acid Lewis Base

Conjugate Acids and Bases (Based on Bronsted-Lowry Classification) Conjugate Base: The substance that remains after an B-L acid has given up a proton (H + ). Conjugate Base: The substance that remains after an B-L acid has given up a proton (H + ). Conjugate Acid: The substance formed when a B-L base has gained a proton. Conjugate Acid: The substance formed when a B-L base has gained a proton. ex: HCl (aq) + H 2 O (l)  Cl - (aq) + H 3 O + (aq) AcidBase Conjugate Base Conjugate Acid Table 15.6: The stronger the acid, the weaker its conjugate base. Equilibrium favors weak acid/base formation.

Amphoteric Compounds Can behave as an acid or base, depending on the strength of the acid or base with which they combine. Can behave as an acid or base, depending on the strength of the acid or base with which they combine. Examples: Examples: – Water – Ammonia

Acid Reactions Neutralization: Neutralization: HCl (aq) + NaOH(aq)  NaCl (aq) + H 2 O (l) HCl (aq) + NaOH(aq)  NaCl (aq) + H 2 O (l) Acid Formation from Acid Anhydrides: Acid Formation from Acid Anhydrides: SO 3 (g) + H 2 O (l)  H 2 SO 4 (aq) SO 3 (g) + H 2 O (l)  H 2 SO 4 (aq) Base Formation from Basic Anhydrides: Base Formation from Basic Anhydrides: Na 2 O (s) + H 2 O(l)  2NaOH Na 2 O (s) + H 2 O(l)  2NaOH Acid Anhydride Acid Rain Basic Anhydride

Aqueous Solutions and pH Self Ionization of Water Self Ionization of Water –Water also supplies H 3 O + and OH - ions. H 2 O (l) + H 2 O (l) H 3 O + (aq) + OH - (aq) H 2 O (l) + H 2 O (l) H 3 O + (aq) + OH - (aq) 1.0 x M Conductivity Experiments show the concentrations of ions at 25 °C: 1.0 x M Ionization Constant of Water, K w Ionization Constant of Water, K w K w = [H 3 O + ][OH - ] = [[ K w = [H 3 O + ][OH - ] = [1.0 x M][1.0 x M] K w = 1.0 x M 2 Constant at a given temperature

Neutral, Acidic, and Basic Solutions Neutral: Neutral: [HO + ] = [OH - ] [H 3 O + ] = [OH - ] Acids: Acids: [HO + ] > [OH - ] [H 3 O + ] > [OH - ] Bases: Bases: [HO + ] < [OH - ] [H 3 O + ] < [OH - ] Determine the hydronium and hydroxide ion concentrations in a 1 x M HCl solution.

pH Scale A more convenient way to express acidity A more convenient way to express acidity pH = -log[H 3 O + ] pH = -log[H 3 O + ] pOH = -log[OH - ] pOH = -log[OH - ] pH + pOH = 14.0 pH + pOH = 14.0 Find the pH and pOH of a 1x M solution of acetic acid. Find the pH and pOH of a 1x M solution of acetic acid.

Indicators and Titration Acid-Base Indicators: Compounds whose colors are sensitive to pH (weak acid or base). Acid-Base Indicators: Compounds whose colors are sensitive to pH (weak acid or base). Titration: Method used to determine an unknown concentration of solution (pg.500) Titration: Method used to determine an unknown concentration of solution (pg.500)

Equivalence Point The point at which the 2 solutions used in a titration are present in equal amounts. The point at which the 2 solutions used in a titration are present in equal amounts. End Point: The point in a titration during which an indicator changes color. End Point: The point in a titration during which an indicator changes color.

Molarity Determination from Titration Because moles of acid=moles of base in a titration AND M = moles/Liter, THEN Because moles of acid=moles of base in a titration AND M = moles/Liter, THEN M A V A /C A = M B V B /C B M A V A /C A = M B V B /C B In a titration, 27.4 ml of M NaOH is added to a 20.0 ml sample of HCl solution of unknown concentration. What is the molarity of the acid solution In a titration, 27.4 ml of M NaOH is added to a 20.0 ml sample of HCl solution of unknown concentration. What is the molarity of the acid solution