I. Intro to Acids & Bases (p.236-241) Definitions Properties Uses Ch. 7 - Acids & Bases I. Intro to Acids & Bases (p.236-241) Definitions Properties Uses

HCl + H2O  H+ + Cl– H3O+ + Cl– A. Definitions Acids Ionize to form hydrogen ions (H+) then hydronium ions (H3O+) in water HCl + H2O  H+ + Cl– H3O+ + Cl–

NH3 + H2O  NH4+ + OH- A. Definitions Bases Dissociate or ionize to form hydroxide ions (OH-) in water NH3 + H2O  NH4+ + OH-

A. Definitions Indicator substance that changes color in an acid or base Examples: litmus - red/blue phenolphthalein - colorless/pink goldenrod - yellow/red red cabbage juice - pink/green

B. Properties ACIDS BASES sour taste corrosive electrolytes turn litmus red react with metals to form H2 gas bitter taste corrosive electrolytes turn litmus blue slippery feel

C. Uses ACIDS H3PO4 - soft drinks, fertilizer, detergents H2SO4 - fertilizer, car batteries HCl - gastric juice HC2H3O2 - vinegar

C. Uses BASES NaOH - lye, drain and oven cleaner Mg(OH)2 - laxative, antacid NH3 - cleaners, fertilizer

Acids and Bases in Solution Acids in Solution Acids are made of a H+ ion and an Anion (a negatively charged ion) In water, acids dissociate (breakdown) into H+ and anions 1. HCl  H+ + Cl- Bases in solution Most bases release hydroxides ions into the water 1. NaOH  Na+ + OH- 2. NH3 + H2O  NH4 + OH- 8

Acid / Base Reactions When Acids and Bases are combined a Neutralization reaction produces water and a salt 1. Hydrochloric Acid and Sodium Hydroxide yields water and Sodium Chloride a. HCl + NaOH  H2O + NaCl B. H+ + Cl- + Na+ + OH-  H2O + NaCl 2. Salt is an ionic compound formed from an acid / base reaction (neutralization) 9

II. Strength of Acids & Bases (p. 242-247) Strong vs. Weak pH Ch. 7 - Acids & Bases II. Strength of Acids & Bases (p. 242-247) Strong vs. Weak pH

A. Strong vs. Weak Strong Acid/Base 100% ions in water strong electrolyte HCl, HNO3, NaOH, LiOH - + Weak Acid/Base few ions in water weak electrolyte HC2H3O2, NH3 - +

ConcepTest Which of the following "molecular" pictures best represents a concentrated solution of the weak acid HA? A B

Strength of Acids Remember Acids are compounds that: Release free Hydrogen ions into solution (H+) Reacts with metals and carbonates Turns blue litmus paper red Tastes sour (never taste) Are corrosive, eating away “Need-to-Know “Acids”: Hydrochloric HCl Nitric Acid HNO3 Sulfuric Acid H2SO4 Carbonic Acid H2CO3 13

Strength of Bases Remember Bases are compounds that: 1. Release hydroxide ions (OH-) into solution ii. Have a bitter taste (never taste any solution unless told to do so) iii. feel slippery iv. React with indicators like litmus by turning red litmus blue v. have a pH greater than 7.0 “Need-to-Know “Bases”: Sodium Hydroxide NaOH Potassium Hydroxide KOH Calcium Hydroxide Ca(OH)2 Ammonia NH3 14

B. pH Scale pH a measure of the concentration of H+ or H3O+ ions in solution measured with a pH meter or an indicator with a wide color range 7 INCREASING ACIDITY NEUTRAL BASICITY 14

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

Water & pH pH = -(log[H+])= -(log[10-7]) pH=- (-7) = pH 7 At equilibrium, the concentration of H+ (Hydronium) is 10-7 so we can calculate the pH of water at equilibrium as: pH = -(log[H+])= -(log[10-7]) pH=- (-7) = pH 7 pH scale goes from 0 to 14 17

ConcepTest Is the following statement TRUE or FALSE? A strong acid has a lower pH than a weak acid. FALSE - Strong/weak refers to amount of ionization whereas pH refers to concentration of H+.

Digestion and pH What is Digestion? Digestion breaks down food (complex molecules) into smaller molecules It has two parts (Mechanical and Chemical) Where does mechanical digestion start? Your Mouth (chewing)

Digestion and pH Chemical Digestion is helped by pH levels and enzymes (catalysts) Where does chemical digestion start? Your mouth Mouth: pH is near 7, amylase enzymes start to break down carbohydrates (try the bread test) Stomach; pH is near 2 (acidic) and pepsin enzymes break down proteins Small Intestine: pH is near 8 (basic) and enzymes finish breaking down carbs, fats and proteins

Digestion and pH http://www.youtube.com/watch?v=tTZUBOhm6xw