Chapter 14: Acids and Bases

Chapter 14: Acids and Bases

Common Acids

Lactic Acid—milk

Acetic Acid-vinegar

Phosphoric Acid-tart flavor in carbonated beverages

Citric Acid-lemons, oranges, grapefruit

Malic acid- apples

Tartaric acid-grape juice

Common Bases

Household ammonia

Sodium hydroxide-lye

Magnesium hydroxide-milk of magnesia

Aluminum hydroxide-antacid

Sodium hydrogen cabonate-baking soda

Acid Properties

Aqueous solutions of acids have a sour taste.
Acids change the color of acid-base indicators.
Some acids react with active metals and release hydrogen gas, H2.
Acids react with bases to produce salts in water. (neutralized)
Acids conduct electric current.

Acid Nomenclature

Binary acid—an acid that contains only two different elements

Hydrogen and one more electronegative element

Binary Acid Nomenclature

The name of a binary acid begins with the prefix hydro-.
The root of the name of the second element follows this prefix.
The name ends with the suffix –ic.

Oxyacid-an acid that is a compound of hydrogen, oxygen, and a third element, usually a nonmetal.

Names of oxyacids are based on the anion name.

No hydro in these names

Some Common Industrial Acids

Sulfuric Acid

Most commonly produced industrial chemical

More than 47 million tons are made per year in US alone

Attracts water so is a good dehydrating agent

Removes water from gases

Removes water from sugar and other organic compounds

Nitric Acid

Pure is volatile and unstable

Dissolving in water makes more stable

Stains proteins yellow

Suffocating odor

Phosphoric Acid

Used mainly in fertilizers and animal feeds

Dilute has a sour taste

Flavoring agent in beverages

Cleaning agent in dairy equipment

Also making detergents and ceramics

Hydrochloric Acid

Stomach acid

“pickling” iron and steel

industrial cleaning agent

concentrated is commonly called muriatic acid—used to clean masonry and maintain swimming pools

Acetic Acid

Pure is called glacial acetic acid

Freezing point of 17 degrees Celsius

Making plastics

Food supplements

Fungicide

Bases Properties

Aqueous solutions of bases taste bitter.
Bases change the color of acid-base indicators.
Dilute aqueous solutions of bases feel slippery.
Bases react with acids to produce salts and water.
Bases conduct electric current.

Arrhenius Acids and Bases

Arrhenius acids—compound that increases the concentration of hydrogen ions, H+, in aqueous solution.

Arrhenius base—compound that increases the concentration of hydroxide ions, OH-, in aqueous solution

Aqueous Solutions of Acids

Water solutions of Arrhenius acids are called aqueous acids

All are electrolytes

Hydrogen ion represented as hydronium ion H3O+

HNO3 (l) + H2O (l) H3O+ (aq) + NO3- (aq)

Strength of Acids

Strong acid ionizes completely in aqueous solution

Weak acid releases few hydrogen ions in aqueous solution

Aqueous Solutions of Bases

Metal with an OH group

Dissolves in water completely

Some bases produce an OH group when they react with water

Strength of Bases

Depends on the amount that the base dissociates

Strong bases are strong electrolytes

Section 2:Acid-Base Theories

Arrhenius definition of acids and bases works most times

Bronsted-Lowry Acids and Bases

1923-Danish-chemist-J.N. Bronsted and English chemist –T. M. Lowry independently

Bronsted-Lowry Acids-molecule or ion that is a proton donor

All acids donate protons to water

Bronsted-Lowry base- molecule or ion that is a proton acceptor

Bronsted-Lowry acid-base reaction—protons are transferred from one reactant to another

Monoprotic Acid—Acid that can donate only one proton per molecule

Perchloric acid—HClO4

Hydrochloric Acid—HCl

Nitiric Acid—HNO3

Polyprotic Acid—acid that can donate more than one proton per molecule

Sulfuric Acid—H2SO4

Phosphoric Acid-H2PO4

Lose protons one at a time

Diprotic Acid—acid that has 2 protons to donate

H2SO4 + H2O H3O+ + HSO4-

HSO4- + H2O H3O+ + SO42-

Triprotic Acid—acid that has 3 protons to donate

H3PO4 + H2O H3O+ + H2PO4-

H2PO4- + H2O H3O+ + HPO42-

HPO42- +H2O H3O+ + PO43-

Lewis Acids—an atom, ion, or molecule that accepts an electron pair to form a covalent bond

Broadest of three definition

Applies of anything with an electron

Formula need not include hydrogen

Need to do Lewis Dot Structures to see these

Do NOT have to be aqueous solutions can be in any phase

Lewis Base—atom, ion, or molecule that donates an electron pair to form a covalent bond

Lewis acid-base reactions—formation of one or more covalent bonds between an electron-pair and an electron-pair acceptor

Section 3: Acid-Base Reactions

Conjugate Base—species that remains after a Bronsted-Lowry acid has given up a proton is the conjugate base of that acid

HF + H2O F- + H3O+

Acid Conjugate base

The species that is formed when a Bronsted-Lowry base gains a proton is the conjugate acid of that base

HF + H2O F- + H3O+

Base Conjugate acid

HF + H2O F- + H3O+

Acid 1 base 2 base 1 acid 2

Strength of Conjugate Acids and Bases

Hydrochloric acid is a strong acid

Gives up protons readily

Cl- ion has little tendency to attract a proton

The stronger an acid the weaker its conjugate base

The stronger a base the weaker its conjugate acid

HClO4 + H2O H3O+ + ClO4-

Stronger acid stronger base Weaker acid weaker base

Proton transfer reactions favor the production of the weaker acid and the weaker base

See table page 485

Amphoteric Compounds

Any species that can react as either an acid of a base is described as amphoteric.

Water is an amphoteric compound

-OH in a molecule

molecules with an –OH can be amphoteric

to be acidic water must attract hydrogen from a hydroxyl group

works better the more polar the –OH

increase polarity increase acidity

the compound is affected by the number of oxygen atoms connecter to the –OH

larger number of oxygen the more acidic

Basic Cr(OH)2

Amphoteric Cr(OH)3

Acidic H2CrO4

Neutralization Reactions

Baking soda = sodium bicarbonate and tartaric acid

Escaping CO2 causes food to rise

Also antacids for stomach

Strong Acid-Strong Base Neutralization

HCl + NaOH NaCl + H2O

NaOH Na+ + OH-

HCl + H2O H3O+ + Cl-

Overall ion equation

H3O+ +Cl- + Na+ + OH- Na+ +Cl- + 2H2O

Net ionic equation

H3O+ + OH- 2H2O

Neutralization is the reaction of hydronium ions and hydroxide ions to form water molecules

Salt—ionic compound composed of a cation from a base and an anion for an acid

Neutralizations result in water and salt

Acid Rain

NO, NO2, CO2, SO2 and SO3 produced in many industrial processes

Mix with water to form acids

Rainwater is slightly acidic

Can be very acidic—acid rain

Causes damage to statues and ecosystem

1970 acid rain is causing fish populations to drop

Clean Air Act of 1990—limit set on amount of SO2 that power plants are permitted to emit

Has decrease the amount of acid rain