Chapter 13 Acids and Bases What are acids and Bases? A. Properties of Acids -tastes sour -conducts electricity -turn blue litmus paper red -reacts with bases to form water and salts -have pH less than 7

Naming Acids Two Types of Acids a. Binary Acid -contains only H and one other element Naming Binary Acids 1. Name begins with prefix hydro- 2. Root of second element follows hydro and ends with the suffix -ic

Examples of Binary Acids Hydrofluoric acidHF Hydrochloric acidHCl Hydrobromic acidHBr Hydrosulfuric acidH 2 S

Acids cont. b. Oxyacid - acid that contains H, O, and a third element,usually a nonmetal Naming Oxyacids 1. Root of the anion plus the suffix –ic followed by the word acid

Examples of Oxyacids Acetic acidacetate Carbonic acidcarbonate Nitric acidnitrate Phosphoric acidphosphate Sulfuric acidsulfate

Properties of Bases - tastes bitter - Feels slippery - Turns red litmus paper blue - Reacts with acids to form water and salts - Have a pH greater than 7

Bases cont. Naming Bases - Element name followed by hydroxide - There are a few exceptions: AmmoniaNH 3 AnilineC 6 H 5 NH 2

Acid-Base Theories Arrhenius Acids and Bases 1. Arrhenius Acid acids in water produce H + ions HNO 3 (aq)  H + (aq) + NO Arrhenius Base bases in water produce OH - KOH(s)  K + (aq) + OH - (aq)

Cont. Bronsted-Lowry Acids and Bases -Acids are proton(H+) donors H 2 CO 3 (aq)+H 2 O(l)  H 3 O + (aq)+HCO 3 - (aq) (acid) (base) (C.A.) (C.B.) -Bases are proton acceptor NH 3 (aq) + H 2 O(l)  NH 4 + (aq) + OH - (aq) base acid C.A. C.B. Conjugate acid- ion formed when a base has accepted a H + Conjugate base- ion formed when an acid has donated a H +

How are weak acids and bases compared? Acid-dissociation constant(K a ) - ratio of concentrations of the products to the reactants for a weak acid - Example CH 3 COOH(aq) + H 2 O(l)  CH 3 COO - (aq) + H 3 O + (aq) K a = [CH 3 COO - ] [H 3 O + ] [CH 3 COOH]

Cont. Base-dissociation constant(K b ) -ratio of concentrations of the products to the reactants for a weak base NH 3 (aq) +H 2 O(l)  NH 4 + (aq) + OH - (aq) K b = [NH 4 + ] [OH - ] [NH 3 ]

The pH scale Is the negative of the common logarithm of the hydronium ion concentration Ranges from 0-14 We use the following equation: pH= -log[H 3 O + ]

Self-Ionization Constant of Water 2H 2 O(l)  H 3 O + (aq) + OH - (aq) K w = [H 3 O + ] [OH - ] K w = 1.00 x at 25° C

Determining [H 3 O + ] and [OH - ] with K w Example What is [OH - ] in a 3.00x M solution of HCl? HCl(g) + H 2 O(l)  H 3 O + (aq) +Cl - (aq) 2H 2 0(l)  H 3 O + (aq) + OH - (aq) What do we know? K w = 1.00 x [H 3 O + ]= 3.00 x 10 -5

Using Logarithms in pH calculations 1. Calculating pH from [H 3 O + ] pH= -log [H 3 O + ] 2. Calculating [H 3 O + ] from pH [H 3 O + ] = 10 -pH

Examples of pH What is the pH of a M solution of HNO 3, a strong acid? [HNO 3 ]= M or 1.0 x M pH= -log[1.0 x10 -4 ] pH= 4.00

Examples cont. What is the pH of a.0136 M solution of KOH, a strong base? [OH - ]=.0136 M K w = 1.00 x Kw= [H 3 O + ][OH - ] pOH= -log[OH - ] pH + pOH = 14

Calculating [H 3 O + ] and [OH - ] from pH What are the concentrations of the hydronium and hydroxide ions in a sample of rain that has a pH of 5.05? [H 3 O + ] = = 8.9 x M Since pH + pOH = 14 pOH= 8.95 so [OH-] = = 1.1 x M

Calculating K a /K b for a weak acid or base A vinegar sample is found to have.837 M CH 3 COOH. Its hydronium concentration is found to be 3.86 x mol/L. Calculate K a for acetic acid. What do we know? [CH 3 COOH]=.837 M [H 3 O + ]= 3.86 x M CH 3 COOH(aq)+ H 2 O(l)  H 3 O + (aq)+CH 3 COO - (aq)

Neutralization and Titrations Neutralization Reaction - a reaction between an acid and a hydroxide base that results in a salt and water HCl + NaOH  NaCl + H 2 O

Titrations - a procedure in which a solution of known concentration is used to determine the concentration of a second unknown solution Equivalence Point - the point at which a neutralization reaction is complete

Titrations cont. How do we know when the equivalence point has been reached? You use an indicator A substance that changes its color as it reacts with either an acid or base The instant the indicator changes color is called the End Point Common indicators are red cabbage juice, litmus, bromthymol blue, and phenolphthalein

Titration Calculations Suppose that in the titration of 40. mL of vinegar, 20.mL of.50 M NaOH were needed to reach the equivalence point. What is the molarity of the acetic acid in the vinegar? NaOH(aq)+CH 3 COOH(aq)  NaCH 3 COO(aq) + H 2 O(l) What do we know? Volume of NaOH= 20. Ml [NaOH]=.50 M Volume of vinegar = 40. ml