acids and bases: experimental definitions

Acids and Bases: Experimental Definitions

Acids:taste sourturn litmus redreact with active metals to release hydrogen gasreact with bases to form water and a salt

Acids and Bases: Experimental Definitions

Bases:taste bitterturn litmus bluefeel slipperyreact with acids to form water and a salt

Acids and Bases

Acids, Bases, and SaltsArrhenius TheoryAcid: a molecular substance that ionizes in aqueous solution to form hydrogen ions (H+)

Acids, Bases, and SaltsArrhenius TheoryBase: a substance that produces hydroxide ions (OH-) in aqueous solution

Acids, Bases, and Salts

Neutralization: When an acid reacts with a base, the properties of each are neutralized and the products are water and a salt.

Acid + Base --> Water + Salt

Acids, Bases, and Salts

Limitations of the Arrhenius Theory- H+ ions do not exist in water solution. Protons

react with water to form hydronium ions. (H3O+)

H+ + H2O --> H3O+

- The Arrhenius Theory does not explain the basicity of ammonia and similar compounds.

- It only applies to reactions in aqueous solution.

Acids, Bases, and Salts

Brønsted-Lowry Theory

Acid: proton donorHA + H2O --> H3O+ + A-

Base: proton acceptorNH3 + H2O --> NH4

+ + OH-

Nonmetal oxides are acidic

SO3 + H2O --> H2SO4

Metal oxides are basic.Example:Lime (calcium oxide) reacts with water to form slaked lime (calcium hydroxide).

CaO + H2O --> Ca(OH)2

Strong and Weak Acids and Bases

Strong acids ionize completely in water solution. 100%

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

Weak acids only partially ionize in water solution.

HCN(aq) --> H+(aq) + CN-(aq)

Strong and Weak Acids and Bases

Strong bases ionize completely in water solution. 100%

NaOH(aq) --> Na+(aq) + OH-(aq)

Weak bases only partially ionize in water solution.

NH3(aq) + H2O --> NH4+(aq) + OH-(aq)

Neutralization

During neutralization, an acid reacts with a base, forming water and a salt.

The pH Scale

pH is a means of expressing the acidity or basicity of a solution.

The pH ScalepH means “power” of hydrogen.

pH = -log[H+]

The pH Scale

Acid Rain

Nonmetal oxides present in air react with water, forming acidic solutions. Rain with a pH of less than 5.6 is considered to be acid rain. Carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen monoxide (NO), and nitrogen dioxide (NO2) are the major nonmetallic oxides responsible for acid rain formation.

Antacids: A Basic RemedyHyperacidity is when the stomach secretes too much acid. Antacids are often taken to neutralize excess acid and reduce the symptoms of hyperacidity.

Excessive use of antacids can lead to an increase in the pH of blood, a condition known as alkalosis.

Antacids: A Basic Remedy

Antacids: A Basic RemedySubstance Formula Product(s)

sodium bicarbonate

NaHCO3 baking soda

calcium carbonate

CaCO3 Tums®

aluminum hydroxide

Al(OH)3 Amphojel®

magnesium hydroxide

Mg(OH)2 Milk of Magnesia®

Acids and Bases in Industry and at Home

Sulfuric acid is the leading chemical substance produced in the U.S. It is used to manufacture fertilizers and industrial chemicals. It is the acid of automotive batteries. Production is 40 billion kg/year.

Acids and Bases in Industry and at Home

Hydrochloric acid has a number of uses. It is used as a rust remover, it removes lime from mortar and household plumbing fixtures. It can be purchased from hardware stores as muriatic acid. Annual U.S. production is 4 billion kg.

Acids and Bases in Industry and at Home

Lime (CaO) is produced by heating limestone (CaCO3).

CaCO3 + heat --> CaO + CO2

Lime can be made by reacting with water to make calcium hydroxide (Ca(OH)2). Lime is used to make mortar and cement and to sweeten soil. Annual U.S. production is 22 billion kg.

Acids and Bases in Industry and at Home

Sodium hydroxide, also known as lye, can be purchased for home use as oven cleaner or drain cleaners. It is used commercially to make soap. Annual U.S. production is 9 billion kg.

Acids and Bases in Industry and at Home

Ammonia is produced for use as fertilizer and in household cleaning products. Production is about 11 billion kg/year.

Acids and Bases in Health and Disease

Concentrated acids and bases are corrosive to tissue and are health hazards. They can denature proteins in living cells.

The human body has wonderful mechanisms for maintaining the proper pH of tissue, blood, and body fluids.