Chapter 15Chapter 15

Acids and BasesAcids and Bases

pH is a measure of the pH is a measure of the HH33O O ++ concentration. concentration.

A Neutral SolutionA Neutral Solution

Has a pH of exactly 7. Has a pH of exactly 7. Contains equal amounts of Contains equal amounts of

hydronium ions and hydroxide hydronium ions and hydroxide ions. ions.

Pure Water: 2HPure Water: 2H22O --> HO --> H33O O ++ + + OHOH - -

AcidsAcids

A. PropertiesA. Properties

1. taste sour1. taste sour

2. change the color of litmus paper to 2. change the color of litmus paper to redred

3. react with metals to produce 3. react with metals to produce hydrogen gashydrogen gas

4. react with bases to produce a “salt” 4. react with bases to produce a “salt” and Hand H22O O (“salt” = ionic (“salt” = ionic compd.) compd.)

- neutralizes the acid- neutralizes the acid

5. some conduct electric current5. some conduct electric current

Naming AcidsNaming Acids

1. 1. binary acidsbinary acids – – contain only 2 contain only 2 different elements different elements

(one is hydrogen)(one is hydrogen)

a) prefix= hydroa) prefix= hydro

b) b) use the first half of the 2use the first half of the 2ndnd element’s nameelement’s name

c) suffix = icc) suffix = ic

Ex. #1 HF = hydrofluoric acidEx. #1 HF = hydrofluoric acid

#2 HCl = hydrochloric acid#2 HCl = hydrochloric acid

#3 HBr = hydrobromic acid#3 HBr = hydrobromic acid

2. 2. oxyacidsoxyacids – – compds. made of H, O, and a 3compds. made of H, O, and a 3rdrd elementelement

a) name the polyatomic ion in the acida) name the polyatomic ion in the acid

b) change the ending of the ionb) change the ending of the ion

- if it ends in - if it ends in ateate, change it to , change it to icic

- if it ends in- if it ends in ite ite, change it to , change it to ousous

Ex. #1 HNOEx. #1 HNO33 = (nitrate) = nitric acid = (nitrate) = nitric acid

Ex. #2 HCEx. #2 HC22HH33OO22 = (acetate) = acetic = (acetate) = acetic acidacid

Ex. #3 HEx. #3 H22SOSO44 = (sulfate) = sulfuric = (sulfate) = sulfuric acidacid

Common AcidsCommon Acids

1. 1. Sulfuric – HSulfuric – H22SOSO44 – most common – most common industrial acid; used in petroleum refining, industrial acid; used in petroleum refining, making fertilizers, car batteriesmaking fertilizers, car batteries

2. 2. Nitric – HNONitric – HNO33 – very unstable; used in – very unstable; used in making explosives, dyes, plastics, rubbermaking explosives, dyes, plastics, rubber

3. 3. Phosphoric – HPhosphoric – H33POPO44 – used as a – used as a flavoring agent in beverages and for making flavoring agent in beverages and for making detergentsdetergents

4. 4. Hydrochloric – HClHydrochloric – HCl – produced by – produced by stomach during digestion; used in a dilute form stomach during digestion; used in a dilute form in swimming pools (called muriatic acid)in swimming pools (called muriatic acid)

5. 5. Acetic – HCAcetic – HC22HH33OO22 – contained in – contained in vinegar; used in making plastics and food vinegar; used in making plastics and food supplementssupplements

BasesBases

A. PropertiesA. Properties

1. taste bitter (ex. Soap)1. taste bitter (ex. Soap)

2. changes the color of litmus 2. changes the color of litmus paper to bluepaper to blue

3. feel slippery3. feel slippery

4. reacts with acids to produce a 4. reacts with acids to produce a “salt” and water“salt” and water

- neutralizes the base- neutralizes the base

5. conduct electricity5. conduct electricity

Definitions of Acids and BasesDefinitions of Acids and Bases

ArrheniusArrhenius

1. 1. Arrhenius acidArrhenius acid – compd. that – compd. that produces Hproduces H++ in aqueous solution in aqueous solution

a) Remember that Ha) Remember that H+ + reacts with Hreacts with H22O to produce HO to produce H33OO++

ex. HNOex. HNO33 + H + H22O O H H33OO++ + NO + NO33--

b) b) strong acidsstrong acids – one that completely ionizes in – one that completely ionizes in aqueous solutionaqueous solution

ex. HCl and HNOex. HCl and HNO33

c) c) weak acidsweak acids –are weak electrolytes (ionize only –are weak electrolytes (ionize only little)little)

ex. HCex. HC22HH33OO22

2. 2. Arrhenius baseArrhenius base – compd. that produces – compd. that produces OHOH-- in aqueous solution (most will have in aqueous solution (most will have OH in their formula)OH in their formula)

a) a) alkalinealkaline – when a base completely dissociates in – when a base completely dissociates in

water to yield OHwater to yield OH- - (aq)(aq)

ex. NaOH (s) ex. NaOH (s) Na Na++ (aq) + OH (aq) + OH-- (aq)(aq)

All group 1 metals are “alkali” metals and All group 1 metals are “alkali” metals and are alkaline basesare alkaline bases

b) b) strong basesstrong bases – strong electrolytes; – strong electrolytes; completely dissociatescompletely dissociates

ex. NaOH, KOHex. NaOH, KOH c) c) weak basesweak bases – not very soluble in water so – not very soluble in water so they don’t give off many OHthey don’t give off many OH-- ions ions

ex. Mg(OH)ex. Mg(OH)22 and NH and NH33 (ammonia)(ammonia)

NHNH33 + H + H22O O NH NH44++ + OH + OH--

Neutralization ReactionsNeutralization ReactionsA. Strong Acid + Strong BaseA. Strong Acid + Strong BaseNaOH(aq)+HCl(aq) NaOH(aq)+HCl(aq) NaCl(aq) NaCl(aq)

+HOH(l)+HOH(l)NaOH NaOH Na Na++ (aq) + OH (aq) + OH-- (aq) (aq)

HCl HCl H H++(aq) + Cl(aq) + Cl-- (aq) (aq)

B. B. Neutralization RxnNeutralization Rxn – rxn of a – rxn of a strong acid and a strong base to form strong acid and a strong base to form water and a salt water and a salt

1. 1. SaltSalt – ionic compound (formed – ionic compound (formed from the rxn of an acid and a base)from the rxn of an acid and a base)

Acid RainAcid Rain

- Many industrial processes produce - Many industrial processes produce NO, NONO, NO22, CO, CO22, SO, SO22, and SO, and SO33 gases gases which dissolve in atmospheric water which dissolve in atmospheric water to produce acidic solutions that come to produce acidic solutions that come down as acid rain or snow.down as acid rain or snow.

SOSO33 + H + H22O O H H22SOSO44

- Many buildings made of CaCO- Many buildings made of CaCO33 (marble)(marble)

CaCOCaCO33 + H + H33OO++ Ca Ca2+2+ + CO + CO22 + H + H22OO

The acid (HThe acid (H33OO++)eats away at the )eats away at the marblemarble

IndicatorsIndicators

Compounds that show a color Compounds that show a color change in an acid or base.change in an acid or base.

Most indicators are weak organic Most indicators are weak organic acids or bases that react with ions in acids or bases that react with ions in solution. It is this chemical reaction solution. It is this chemical reaction that produces the color change. that produces the color change.

Indicators are used to determine Indicators are used to determine the approximate pH of a the approximate pH of a

substance.substance. Two common indicators areTwo common indicators are

Litmus - Litmus - Acids turn blue litmusAcids turn blue litmus red.red. Bases turn red litmusBases turn red litmus blue.blue.

Phenolphthalein - Phenolphthalein - Colorless in an acid. Colorless in an acid. Very faint pink in a neutral solution. Very faint pink in a neutral solution. Bright pink in a base. Bright pink in a base.

pH Meter: A device used to measure the pH Meter: A device used to measure the exact pH of a solution. exact pH of a solution.