Acids and

Bases

Take notes on your own paper today…

Write down things that are in yellow

You’ll need this information to answer the lab questions

Svante Arrhenius• He was a Swedish chemist (1859-

1927), and a Nobel prize winner in chemistry (1903)

• one of the first chemists to explain the chemical theory of the behavior of acids and bases

• Dr. Hubert Alyea (professor emeritus at Princeton University) was the last graduate student of Arrhenius.

Hubert N. Alyea (1903-1996)

1. Arrhenius Definition - 1887

• Acids produce hydrogen ions (H1+) in aqueous solution (HCl → H1+ + Cl1-)

• Bases produce hydroxide ions (OH1-) when dissolved in water.

(NaOH → Na1+ + OH1-)

Svante Arrhenius (1859-1927)

2. Brønsted-Lowry – 1923• A broader definition than Arrhenius• Acid is hydrogen-ion donor (H+ or proton);

base is hydrogen-ion acceptor.• Acids and bases always come in pairs.• HCl is an acid.

–When it dissolves in water, it gives it’s proton to water.

HCl(g) + H2O(l) ↔ H3O+(aq) + Cl-

(aq)

• Water is a base; makes hydronium ion.

Johannes Brønsted Thomas Lowry (1879-1947) (1874-1936) Denmark England

Properties of Acids

Acids taste sourAcids have a pH lower than 7Acids effect indicatorsBlue litmus turns redUniversal indicator turns red

Acids are proton (hydrogen ion, H+) donors

Acids react with active metals, produce H2

Acids react with carbonates Acids neutralize bases

Acids Effect Indicators

Blue litmus paper turns red in contact with an acid.

Acids Have a pH less than

7

Acids React with Active Metals

Acids react with active metals to form salts and hydrogen gas.

Mg + 2HCl MgCl2 + H2(g)

Acids Neutralize Bases

HCl + NaOH NaCl + H2O

Neutralization reactions ALWAYS produce a salt and water.

Sulfuric Acid

Highest volume production of any chemical in the U.S.

Used in the production of paper

Used in production of fertilizers

Used in petroleum refining

Nitric Acid• Used in the production

of fertilizers• Used in the production

of explosives• Nitric acid is a volatile

acid – its reactive components evaporate easily

• Stains proteins (including skin!)

Hydrochloric Acid• Used in the pickling of

steel• Used to purify

magnesium from sea water

• Part of gastric juice, it aids in the digestion of protein

• Sold commercially as “Muriatic acid”

Phosphoric Acid

o A flavoring agent in sodas

o Used in the manufacture of detergents

o Used in the manufacture of fertilizers

o Not a common laboratory reagent

Acetic AcidUsed in the manufacture

of plasticsUsed in making

pharmaceuticalsAcetic acid is the acid

present in vinegar

Organic AcidsOrganic acids all contain the “carboxyl” group, sometimes several of them.

The carboxyl group is a poor proton donor, so ALL organic acids are weak acids.

Examples of Organic Acids

Citric acid in citrus fruit Malic acid in sour apples Deoxyribonucleic acid, DNA Amino acids, the building blocks of

protein Lactic acid in sour milk and sore

muscles Butyric acid in rancid butter

Acids are Proton Donors

Monoprotic acidsDiprotic acids Triprotic acids

HCl

HC2H3O2

HNO3

H2SO4

H2CO3

H3PO4

Ionization of HCl and formation of hydronium ion,

H3O+

H2O + HCl H3O+ + Cl-

Protondonor

Protonacceptor

Strong Acids vs. Weak Acids

Strong acids are assumed to be 100% ionized in solution (good proton donors).

Weak acids are usually less than 5% ionized in solution (poor proton donors).

HCl

H2SO4 HNO3

H3PO4 HC2H3O2 Organic acids

Effects of acid on the Environment

Rainwater is naturally acidicWHY?When CO2 (gas) + H2O H2CO3 (aqueous) react they formCarbonic acid Carbon dioxide (from the air) dissolves inrainwater, producing carbonic acid, a weak acid The normal pH of rainwater is about 5.6

Effects of acid on the Environment

• Acid rain is rain with a pH less than 5.

•

• Forms when air-polluting gases dissolve in

• Rainwater

• Sulfur dioxide (SO2) Further lowers the pH of rain.

Effects of acid on the Environment

• Environmental Impact of Acid Rain• Dependent on local geology• Hill Country soil is rich in limestone

(CaCO3), which is basic • Limestone neutralizes the effect of acid

rain on lakes

Damages Caused by Acid Rain1) Damage to aquatic life

• In some sensitive lakes and streams, acidification has completely eradicated

• fish species, such as the brook trout, leaving these bodies of water barren. Hundreds of the lakes in the Adirondacks have acidity levels unsuitable for the survival of fish

Damages Caused by Acid Rain (Cont.)

2.) Damage to vegetation

Damages Caused by Acid Rain (Cont.)

3) Damage to outdoor artwork (monuments & statues)

Properties of Bases Bases taste bitterBases have a pH greater than 7 Bases effect indicators

Red litmus turns blueUniversal indicator turns bluePhenolphthalein turns purple

Bases are proton (H+) acceptors and usually have hydroxide ions- OH- Solutions of bases feel slippery Bases neutralize acids

Examples of Bases

Sodium hydroxide (lye), NaOH

Potassium hydroxide, KOH Magnesium hydroxide,

Mg(OH)2

Calcium hydroxide (lime), Ca(OH)2

Bases Effect Indicators

Red litmus paper turns blue in contact with a base. Phenolphthale

in turns purple in a base.

Bases have a pH

greater than 7

Bases Neutralize Acids

Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.

2 HCl + Mg(OH)2

MgCl2 + 2 H2O

Products of Neutralization

HCl + NaOH

H2SO4 + Ca(OH)2

HNO3 + KOH

The products of neutralization are always a ______ and _______.

NaCl + H2O

CaSO4 + 2 H2O

KNO3 + H2O

salt water