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Acids
• Aqueous solutions of acids have a sour taste (never taste chemicals)
• Will change the color of acid-base indicators• Some acids react with active metals and
release hydrogen gas• React with bases to produce salts and water• Acids conduct electric current (varies)
Naming Acids
• Binary acid: contains only two different elements; hydrogen and one other more electronegative element– 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 then ends with the suffix -ic
Naming Oxyacids
• Oxyacid: an acid that is a compound of hydrogen, oxygen, and a third element, usually a nonmetal
Common Industrial Acids
• Sulfuric acid: the most commonly produced industrial chemical in the world– H2SO4
– Used for making: fertilizer, paint, paper, detergents, dyes, batteries for cars, also used in refining
• Nitric acid– HNO3
– Used for making explosives, rubber, plastics, dyes, pharmaceuticals
More Acids• Phosphoric acid– H3PO4
– Most is used directly for manufacturing fertilizers and animal feed, used as a flavoring agent in beverages
• Acetic acid– CH3COOH
– Vinegars, synthesizing chemicals used in making plastics, raw material in production of food supplements
One More Acid
• Hydrochloric acid– HCl– Used to remove surface impurities from metals, as
a cleaning agent, food processing, activation of oil wells, recovery of magnesium from sea water, making other chemicals
– Concentrated HCl is commonly called muriatic acid and can be found in hardware stores
Bases
• Aqueous solutions of bases taste bitter (never taste chemicals)
• 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 (varies)
Common Bases
• Ammonia– NH3
– http://www.rmtech.net/uses_of_ammonia.htm
• NaOH (sodium hydroxide)– http://www.chemicalland21.com/industrialchem/i
norganic/CAUSTIC SODA.htm
Another Base
• Baking soda– NaHCO3
– food & food processing, beverages , pharmaceuticals , animal foodstuffs , household cleaning products , rubber & plastics foam blowing , fire extinguishers & explosion suppression , effluent & water treatment, flue gas treatment , oil drilling , industrial & chemical processes
Svante Arrhenius
• Svante Arrhenius was a Swedish chemist who lived from 1859-1927
• He realized that aqueous solutions of acids and bases conducted electricity
• He then theorized that they produce ions in solution
Arrhenius Acid and Base Theory
• Arrhenius acid: a chemical compound that increases the concentration of hydrogen ions, H+, in aqueous solution
• Arrhenius base: a substance that increases the concentration of hydroxide ions, OH-, in aqueous solution
Aqueous Solutions of Acids
• Acid molecules are polar, so the water molecules attract one or more of the hydrogen ions when the acid dissociates in water
• HNO3(aq) + H2O(l) H3O+(aq) + NO3
-(aq)
Strength of Acids
• Strong acid: one that dissociates completely in aqueous solutions
• Concentration is not linked to strength• Weak acid: one that releases few
hydrogen ions in aqueous solution• When a weak acid is dissolved in water,
the reverse reaction occurs simultaneously
Weak Acid Solution
• HCN(aq) + H2O(l) H3O+(aq) + CN-
(aq)
• The number of the hydrogen atoms in the formula does not indicate acid strength
• Organic acids, that contain COOH are usually weak acids
Aqueous Solutions of Bases
• Most bases are ionic compounds containing a metal cation and the hydroxide anion, so they dissociate in water
Strength of Bases
• Strong base: one that completely dissociates in solution
• Strong bases are also strong electrolytes (as well as strong acids)
• Electrolyte: a substance that dissolves in water to give a solution that conducts an electric current
Strength of Bases
• Bases that are not very soluble do not produce a large number of hydroxide ions when added to water
• They are weak bases• Some bases, like NH3, are soluble, but do
not form many OH- ions, so they are weak
Another Theory
• Chemists noticed that some substances acted like acids and bases, but were not in a water solution
• The Arrhenius theory required an aqueous solution
• Another theory had to be considered
Brønsted-Lowry Theory
• Named for 2 chemists J. N. Brønsted and T. M. Lowry who independently expanded the Arrhenius theory
• Brønsted-Lowry acid: a molecule or ion that is a proton donor (H+ is a proton)
• Brønsted-Lowry base: a molecule or ion that is a proton acceptor
Brønsted-Lowry Acid
• Any Arrhenius acid also qualifies as a Brønsted-Lowry acid, but not vice-versa
• HCl + NH3 NH4+ + Cl-
• A proton is donated by the hydrogen chloride molecule even though it is not aqueous
• Water can also act as a Brønsted-Lowry acid
Monoprotic and Polyprotic Acids• Monoprotic acid: an acid that can donate only
one proton (hydrogen ion) per molecule• Examples: HCl and HNO3
• Polyprotic acid: an acid that can donate more than one proton per molecule
• Examples: H2SO4 and H3PO4
• Diprotic acid: an acid that donates two protons per molecule
Another Theory
• Some species behave like acids and bases even though they do not contain, or react to form, a hydrogen ion
• G. N. Lewis, of Lewis stucture fame, proposed a new theory
Lewis Theory of Acids and Bases
• Lewis acid: an atom, ion, or molecule that accepts an electron pair to form a coordinate covalent bond
• Lewis base: an atom, ion, or molecule that donates an electron pair to form a coordinate covalent bond