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Chapter 19“Acids, Bases,
and Salts”
Properties of Acids & Bases!
electrolytes
turn litmus redsour taste
react with metals to form H2 gas
slippery feel
turn litmus bluebitter taste
ChemASAP
vinegar, milk, soda, apples, citrus fruits
ammonia, lye, antacid, baking soda
electrolytes
don’t react w/metals
“clean” feel
pH < 7 pH > 7Produce OH– ions in H2O
Produce H+ ions in H2O
Properties
• Electrolytes can conduct electricity–Can be strong or weak electrolytes in
aqueous solution
Acids have a pH less than 7
Acids Affect Indicators
Blue litmus paper turns red in contact with an acid.
Acids React with Active Metals
Acids react with active metals to form salts and hydrogen gas:HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
How can you tell if the gas produced is hydrogen?
Acids React with Carbonates
2HC2H3O2 + Na2CO3
2NaC2H3O2 + H2O + CO2
Effects of Acid Rain on Marble(calcium carbonate)
George Washington:BEFORE
George Washington:AFTER
Bases have a
pH greater than 7
Bases Affect Indicators
Red litmus paper turns blue in contact with a base.
Phenolphthalein turns purple in a base.
Vid properties
Different Acid & Base Definitions
Definitions• ArrheniusArrhenius - In aqueous solution (when - In aqueous solution (when
dissolved in water)…dissolved in water)…
HCl + H2O H3O+ + Cl– •AcidsAcids form hydronium ions (H3O+) (or H+)
H
HH H H
H
ClClO O
–+
acidCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Arrhenius said: An acid can be defined as a substance that
yields hydrogen ions (H+) when dissolved in water.
HCl•Pure, dry substance is hydrogen chloride•When dissolved in water it’s hydrochloric acid… it breaks into H+ ions & Cl- ions
2.7
A base can be defined as a substance that yields
hydroxide ions (OH-) when dissolved in water.
NaOH sodium hydroxideKOH potassium hydroxideBa(OH)2 barium hydroxide
Definitions
• ArrheniusArrhenius - In aqueous solution… - In aqueous solution…
•BasesBases form hydroxide ions (OH-)
NH3 + H2O NH4+ + OH-
H
H
HH H
H
N NO O–+
HH
H H
baseCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Video 1
Definitions
• Brønsted-LowryBrønsted-Lowry
HCl + H2O Cl– + H3O+
•AcidsAcids are proton (H+) donors. •BasesBases are proton (H+) acceptors.
conjugate acidconjugate base
baseacid
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Acids and bases come in pairs• A “conjugate base” is the
remainder of the original acid, after it donates it’s proton/hydrogen ion
• A “conjugate acid” is the particle formed when the original base gains a proton/hydrogen ion
• Indicators are weak acids or bases that have a different color from their original acid and base
Definitions
H2O + HNO3 H3O+ + NO3–
CBCAAB
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
H
H
OH O
O
ON
Base Acid
Acids and bases come in pairs• Amphoteric – a substance that can act as both
and acid and base- as water shows
Video 2
Definitions• Lewis –Lewis – same guy who came up with the
Lewis-dot structures
• AcidsAcids are electron pair acceptors. • BasesBases are electron pair donors.
Lewis base
Lewis acid
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Acid Definitions
Lewis acids
Bronsted-Lowry
Arrheniusacids
The Arrhenius model of acids and bases was broadened by the Bronsted-Lowry model.
The Bronsted-Lowry model was broadened by the Lewis model
The Lewis acid-base model is the most general in scope.
Ralph A. Burns, Fundamentals of Chemistry 1999, page 483
Acid – Base Systems
Type Acid Base
Arrhenius H+ or H3O + producer
OH - producer
Bronsted-
Lowry
Proton (H +) donor
Proton (H +) acceptor
Lewis Electron-pair acceptor
Electron-pair donor