Anything in black letters = write it in your notes (‘knowts’) UNIT 6 – Acids & Bases & Redox Rxns Chapter 19 – Acids, Bases, and Salts Chapter 20 – Oxidation-Reduction Rxns Chapter 19 Acids, Bases, and Salts Anything in black letters = write it in your notes (‘knowts’)

Acids Bases 19.1 – Acid-Base Theories Taste sour Dissolve active metals to produce hydrogen gas Turns litmus paper RED Bases Taste bitter Feels slippery on skin (dissolves oils on skin) Turns litmus paper BLUE Have you seen the litmus paper yet?? These are experimental definitions, we need a theoretical…

HCl (aq)  H+ (aq) + Cl- (aq) NaOH (aq)  Na+ (aq) + OH- (aq) Arrhenius’s Definition (~1887) ACID – substance that forms hydrogen (H+) ions in water. HCl (aq)  H+ (aq) + Cl- (aq) HCl is an acid because it produces H+ ions when placed in water. BASES – substance that forms hydroxide (OH-) ions in water. NaOH (aq)  Na+ (aq) + OH- (aq) NaOH is a base because it produces OH- ions when placed in water.

Lewis Acids and Bases (not covered) Bronsted-Lowry Acids/Bases (not covered) Conjugate Acids & Bases (not covered) Lewis Acids and Bases (not covered)

pH = ‘power of the hydrogen ion’ 19.2 – Hydrogen Ions and Acidity The more H+ a substance forms in water, the more acidic the solution becomes. pH = ‘power of the hydrogen ion’ The pH scale is used to describe how acidic or basic (alkaline) a substance is.

[H+] = ‘the hydrogen ion concentration’ Molarity (M) – unit used to express the concentration of a solution mol solute (mol) Molarity = liters of soln (L) anything in [brackets] means the concentration in molarity [H+] = ‘the hydrogen ion concentration’ [OH-] = ‘the hydroxide ion concentration’

pH = ‘power of the hydrogen ion’ Two methods of measuring pH pH = ‘power of the hydrogen ion’ Acid-Base Indicators – change color when a change in pH occurs. pH meters phenolphthalein, litmus, cabbage, etc…

19.3 – Strengths of Acids and Bases not covered…

Acid + Base  Salt + H2O HCl + NaOH  NaCl + H2O 19.4 – Neutralization Reactions Neutralization Rxn – complete rxn of a strong base with a strong acid A neutralization rxn will produce a salt and water. Acid + Base  Salt + H2O HCl + NaOH  NaCl + H2O

Standard – solution of known concentration. Titration – determining the concentration of an unknown solution using a solution whose concentration is known. Standard – solution of known concentration. Equivalence Point – point where the amount of acid equals the amount of base End Point – point where the indicator changes color 11

HCl + NaOH  NaCl + H2O EXAMPLE x M 0.5 M 10.0 mL 20.0 mL 10.0 mL of 0.5 M HCl solution is added to 20.0 mL of NaOH of unknown concentration. What is the concentration of the NaOH? HCl + NaOH  NaCl + H2O x M 0.5 M 10.0 mL 20.0 mL Since the reaction of HCl and NaOH is 1:1 and twice the volume of NaOH was used, the NaOH must half as strong as HCl; [0.25 M].

Always adjust if the rxn is NOT 1:1 EXAMPLE What volume of 0.10 M KOH is required to neutralize 20.0 mL of 0.20 M H2SO4 solution? H2SO4 + 2KOH  K2SO4 + 2H2O 0.20 M 0.10 M 20.0 mL x mL Always adjust if the rxn is NOT 1:1 Since KOH requires twice as many moles as H2SO4, you should double your answer.

Write the balanced chemical equation for each neutralization reaction Sulfuric acid + magnesium hydroxide Phosphoric acid + calcium hydroxide Nitric acid + ammonium hydroxide

Chapter 19 Sample Quiz Questions 1. What color will litmus paper be in an acidic solution? 2. What color will phenolphthalein indicator be in an basic solution? 3. Define an acid in terms of H+ ions. 4. What two products are always formed in an acid-base neutralization reaction? 5. HCl (aq) + KOH (aq)  ______ + _______

19.5 – Salts in Solution not covered…