acids and bases. properties of acids acids taste sour acids effect indicators blue litmus turns...
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ACIDS AND BASES
Properties of AcidsProperties of Acids
Acids taste sour Acids effect indicators
Blue litmus turns red Methyl orange turns red
Acids have a pH lower than 7 Acids are proton (hydrogen ion, H+) donors Acids react with active metals, produce H2
Acids react with carbonates Acids neutralize bases
Acids you must know:Acids you must know:
Strong Acids Weak Acids
Hydrochloric acid, HCl
Nitric acid, HNO3
Sulfuric acid, H2SO4 Phosphoric acid, H3PO4
Acetic acid, HC2H3O2
Properties of BasesProperties of Bases Bases taste bitter Bases effect indicators
Red litmus turns blue Phenolphthalein turns purple
Bases have a pH greater than 7 Bases are proton (hydrogen ion, H+) acceptors Solutions of bases feel slippery
Bases neutralize acids
Examples of BasesExamples of Bases
Sodium hydroxide (lye), NaOH Sodium hydroxide (lye), NaOH Potassium hydroxide, KOH Potassium hydroxide, KOH Magnesium hydroxide, Mg(OH)Magnesium hydroxide, Mg(OH)2 2
Calcium hydroxide (lime), Ca(OH)Calcium hydroxide (lime), Ca(OH)22
Arrhenius Acids and BasesAcids release hydrogen ions in water.Bases release hydroxide ions in water.
An acid is a substance that produces hydronium ions, H3O+, when dissolved in water.
Lewis DefinitionsA Lewis acid is a substance than can accept (and share) an electron pair.A Lewis base is a substance than can donate (and share) an electron pair.
Lewis acids
Lewis Acid
Bronsted-Lowry DefinitionsA Bronsted-Lowry acid is a proton donor; it donates a hydrogen ion, H+.A Bronsted-Lowry base is a proton acceptor; it accepts a hydrogen ion, H+.
Bronsted-Lowry
Arrheniusacids
Acid Definitions
Acid Definitions
Lewis acids
Bronsted-Lowry
Arrheniusacids
The Arrhenius model of acidsand bases was broadened bythe Bronsted-Lowry model.
The Lewis acid-base model isthe most general in scope.
The Lewis definition of an acidincludes any substance thatis an electron pair acceptor;a Lewis base is any substancethat can act as an electron pair donor.
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
Acids are Proton DonorsAcids are Proton Donors
Monoprotic acidsDiprotic acids Triprotic acids
HCl
HC2H3O2
HNO3
H2SO4
H2CO3
H3PO4
Ionization of HCl and Ionization of HCl and formation of hydronium ion, formation of hydronium ion,
HH33OO++
H2O + HCl H3O+ + Cl-
Proton donor
Proton acceptor
Self-Ionization of WaterSelf-Ionization of Water
H2O + H2O H3O+ + OH-
Though pure water is considered a non-conductor, there is a slight, but measurable conductivity due to “self-ionization”
Ion Concentration in Ion Concentration in SolutionsSolutions
KKww – Ionization Constant for – Ionization Constant for WaterWater
In pure water at 25 C:
[H3O+] = 1 x 10-7 mol/L
[OH-] = 1 x 10-7 mol/L
Kw is a constant at 25 C:
Kw = [H3O+][OH-]
Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-
14
pH scale
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
ACID BASE
NEUTRAL
Each step on pH scale represents a factor of 10.
pH 5 vs. pH 6 (10X more acidic)pH 3 vs. pH 5 (100X different)pH 8 vs. pH 13 (100,000X different)
: measures acidity/basicity
10x10x10x100x
H+, OH-, and pHH+, OH-, and pH
Calculating pH, Calculating pH, pOHpOHpH = -log10(H3O+)
pOH = -log10(OH-)
Relationship between pH and Relationship between pH and pOHpOH pH + pOH = 14
Finding [HFinding [H33OO++], [OH], [OH--] from pH, pOH] from pH, pOH
[H3O+] = 10-pH
[OH-] = 10-pOH
Strong Acids vs. Weak AcidsStrong 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
Strong Acid DissociationStrong Acid Dissociation
Weak Acid DissociationWeak Acid Dissociation
Acids Effect IndicatorsAcids Effect Indicators
Blue litmus paper turns red in contact with an acid.
Acids Acids Have a pH Have a pH less than less than
77
Effects of Acid Rain on MarbleEffects of Acid Rain on Marble(calcium (calcium carbonatecarbonate))
George Washington: BEFORE
George Washington: AFTER
Bases Effect Bases Effect IndicatorsIndicators
Red litmus paper turns blue in contact with a base. Phenolphthale
in turns purple in a base.
Bases Bases have a pH have a pH
greater greater than 7than 7
Bases Neutralize Bases Neutralize AcidsAcids
Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O
Acids Neutralize BasesAcids Neutralize Bases
HCl + NaOH NaCl + H2O
Neutralization reactions ALWAYS produce a salt and water.
Neutralization
NeutralizationNeutralization is a chemical reaction between an acid and a base to produce a salt (an ionic compound) and water.
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)base acid salt water
Some neutralization reactions:
H2SO4(aq) + NaOH(aq) Na2SO4 + HOH
sulfuric acid sodium hydroxide sodium sulfate water
HC2H3O2(aq) + Ca(OH)2(aq) Ca(C2H3O2)2 + HOH
acetic acid calcium hydroxide calcium acetate water
2 2
2 2
Neutralization
ACIDACID + BASE + BASE SALT + WATER SALT + WATER
HCl + NaOH HCl + NaOH NaCl + H NaCl + H22OO
HCHC22HH33OO22 + NaOH + NaOH NaC NaC22HH33OO22 + H + H22OO
– Salts can be neutral, acidic, or basic.
– Neutralization does not mean pH = 7.
weak
strong strong
strong
neutral
basic
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Salts
SaltsSalts - Ionic compounds containing a positive ion other than the hydrogen ion and a negative ion other than the hydroxide ion.
i.e., a metal and a non-metal
NaCl(s) + H2O(l) Na1+(aq) + Cl1-(aq)
Formulas and names of common salts
SALT FORMULA Common Name
sodium chloride NaCl (table) salt
sodium nitrate NaNO3 Chile saltpeter
sodium bicarbonate NaHCO3 baking soda
potassium carbonate K2CO3 potash
ammonium chloride NH4Cl sal ammoniac
NaCl