Chapter 15 Acids and Bases

pH is a measure of the H3O + concentration.

A Neutral Solution Has a pH of exactly 7. Contains equal amounts of hydronium ions and hydroxide ions. Pure Water: 2H2O --> H3O + + OH -

Acids A. Properties 1. taste sour 2. change the color of litmus paper to red 3. react with metals to produce hydrogen gas 4. react with bases to produce a “salt” and H2O (“salt” = ionic compd.) - neutralizes the acid 5. some conduct electric current

Naming Acids 1. binary acids – contain only 2 different elements (one is hydrogen) a) prefix= hydro b) use the first half of the 2nd element’s name c) suffix = ic Ex. #1 HF = hydrofluoric acid #2 HCl = hydrochloric acid #3 HBr = hydrobromic acid

2. oxyacids – compds. made of H, O, and a 3rd element a) name the polyatomic ion in the acid b) change the ending of the ion - if it ends in ate, change it to ic - if it ends in ite, change it to ous Ex. #1 HNO3 = (nitrate) = nitric acid Ex. #2 HC2H3O2 = (acetate) = acetic acid Ex. #3 H2SO4 = (sulfate) = sulfuric acid

Common Acids 1. Sulfuric – H2SO4 – most common industrial acid; used in petroleum refining, making fertilizers, car batteries 2. Nitric – HNO3 – very unstable; used in making explosives, dyes, plastics, rubber 3. Phosphoric – H3PO4 – used as a flavoring agent in beverages and for making detergents 4. Hydrochloric – HCl – produced by stomach during digestion; used in a dilute form in swimming pools (called muriatic acid) 5. Acetic – HC2H3O2 – contained in vinegar; used in making plastics and food supplements

Bases A. Properties 1. taste bitter (ex. Soap) 2. changes the color of litmus paper to blue 3. feel slippery 4. reacts with acids to produce a “salt” and water - neutralizes the base 5. conduct electricity

Definitions of Acids and Bases Arrhenius 1. Arrhenius acid – compd. that produces H+ in aqueous solution a) Remember that H+ reacts with H2O to produce H3O+ ex. HNO3 + H2O  H3O+ + NO3- b) strong acids – one that completely ionizes in aqueous solution ex. HCl and HNO3

All group 1 metals are “alkali” metals and are alkaline bases c) weak acids –are weak electrolytes (ionize only little) ex. HC2H3O2 2. Arrhenius base – compd. that produces OH- in aqueous solution (most will have OH in their formula) a) alkaline – when a base completely dissociates in water to yield OH- (aq) ex. NaOH (s)  Na+ (aq) + OH- (aq) All group 1 metals are “alkali” metals and are alkaline bases

b) strong bases – strong electrolytes; completely dissociates ex. NaOH, KOH c) weak bases – not very soluble in water so they don’t give off many OH- ions ex. Mg(OH)2 and NH3 (ammonia) NH3 + H2O  NH4+ + OH-

NaOH(aq)+HCl(aq)  NaCl(aq)+HOH(l) NaOH  Na+ (aq) + OH- (aq) Neutralization Reactions A. Strong Acid + Strong Base NaOH(aq)+HCl(aq)  NaCl(aq)+HOH(l) NaOH  Na+ (aq) + OH- (aq) HCl  H+(aq) + Cl- (aq) B. Neutralization Rxn – rxn of a strong acid and a strong base to form water and a salt 1. Salt – ionic compound (formed from the rxn of an acid and a base)

Acid Rain - Many industrial processes produce NO, NO2, CO2, SO2, and SO3 gases which dissolve in atmospheric water to produce acidic solutions that come down as acid rain or snow. SO3 + H2O  H2SO4 - Many buildings made of CaCO3 (marble) CaCO3 + H3O+  Ca2+ + CO2 + H2O The acid (H3O+)eats away at the marble

Compounds that show a color change in an acid or base. Indicators Compounds that show a color change in an acid or base. Most indicators are weak organic acids or bases that react with ions in solution. It is this chemical reaction that produces the color change.

Indicators are used to determine the approximate pH of a substance. Two common indicators are Litmus - Acids turn blue litmus red. Bases turn red litmus blue. Phenolphthalein - Colorless in an acid. Very faint pink in a neutral solution. Bright pink in a base. pH Meter: A device used to measure the exact pH of a solution.