Acids and Bases Dr. Ron Rusay Spring 2004 © Copyright 2001-2004 R.J. Rusay.
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Transcript of Acids and Bases Dr. Ron Rusay Spring 2004 © Copyright 2001-2004 R.J. Rusay.
Acids and BasesAcids and Bases
Dr. Ron RusayDr. Ron Rusay
Spring 2004Spring 2004
© Copyright 2001-2004 R.J. Rusay© Copyright 2001-2004 R.J. Rusay
Introduction to AqueousIntroduction to Aqueous Acids & Bases Acids & Bases
Acids: taste sour and cause certain dyes Acids: taste sour and cause certain dyes to change color.to change color.
Bases: taste bitter, feel soapy and Bases: taste bitter, feel soapy and cause certain dyes to turn color.cause certain dyes to turn color.
ElectrolytesElectrolytes Aqueous solutions can be categorized into 3 Aqueous solutions can be categorized into 3
types: non-electrolytes, strong electrolytes or types: non-electrolytes, strong electrolytes or weak electrolytes based on their ability to conduct weak electrolytes based on their ability to conduct electricity.electricity.
A solution must have A solution must have ions ions to conduct.to conduct. Pure Water Pure Water does not conduct.does not conduct. Aqueous solutions can be tested for conductivity Aqueous solutions can be tested for conductivity
which will determine the degree of ionization of which will determine the degree of ionization of the solutes.the solutes.
It is possible to have full or partial ionization.It is possible to have full or partial ionization.
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© Copyright 1995-2000 R.J. Rusay© Copyright 1995-2000 R.J. Rusay
Solution Test ApparatusSolution Test Apparatusfor Electrolytes for Electrolytes
04_43 Power Source
(a)(b)(c)+−+++−−−− −++
ElectrolytesElectrolytes Almost all Almost all ionic compoundsionic compounds and a few molecular and a few molecular
compounds are strong electrolytes.compounds are strong electrolytes. Most Most molecular compoundsmolecular compounds are non-conductors. are non-conductors. Conductivity is directly related to the amount of Conductivity is directly related to the amount of
ionization, i.e. ions in solution. Table salt, sodium ionization, i.e. ions in solution. Table salt, sodium chloride, is completely ionized:chloride, is completely ionized:
NaCl(s) + H2O(l) ---> NaCl(aq) ---> 0.10mol Na
+(aq) + Cl -
(aq)
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© Copyright 1995-2000 R.J. Rusay© Copyright 1995-2000 R.J. Rusay
0.00mol 0.10mol 0.10mol
Strong vs. Weak ElectrolytesStrong vs. Weak Electrolytes
Sugar is non-ionized in water and does not conduct. Sugar is non-ionized in water and does not conduct.
What is an acid and how strong is it?What is an acid and how strong is it?
Acids have a proton, Acids have a proton, H+, eg HCl(aq).eg HCl(aq). A strong acid is 100% ionized. For example nitric A strong acid is 100% ionized. For example nitric
acid, acid, HNOHNO3 3 , produces 100% H+ (aq). Other common . Other common
strong acids are sulfuric, Hstrong acids are sulfuric, H22SOSO44 (aq) and (aq) and
hydrochloric, HCl (aq) which also produce hydrochloric, HCl (aq) which also produce 100% H+ (aq). .
Acids & Strong Acids:Acids & Strong Acids:
Dissociation Dissociation of Strong and of Strong and Weak AcidsWeak Acids
A weak acid does A weak acid does not dissociate not dissociate
100%, eg. Acetic 100%, eg. Acetic acid in vinegar.acid in vinegar.
Acid StrengthAcid Strength(continued)(continued)
A weak acid is not 100% ionized. For A weak acid is not 100% ionized. For example acetic acid, example acetic acid, CHCH33COOH,COOH,
produces <100% H+ (aq). Most acids, . Most acids, particularly organic acids, are weak particularly organic acids, are weak acids.acids.
Weak AcidsWeak Acids::
Strong or weak acids? Strong or weak acids?
Strong or weak acids? Strong or weak acids?
A scale to relate acidities. A scale to relate acidities.
Aqueous BasesAqueous Bases Any compound that accepts a proton is a base.Any compound that accepts a proton is a base. The common bases are group IA & IIA metal The common bases are group IA & IIA metal
hydroxide compounds. “hydroxide compounds. “StrongStrong” and “” and “weakweak” are ” are used in the same sense for bases as for acids.used in the same sense for bases as for acids.
StrongStrong = = complete dissociation complete dissociation (100% (100% hydroxide ion is supplied to the solution) An hydroxide ion is supplied to the solution) An example of a weak base is ammonia.example of a weak base is ammonia.
NH3 (g) + H2O(l) NH3 (aq) NH4+
(aq)+ OH-
(aq)
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© Copyright 1995-2001 R.J. Rusay© Copyright 1995-2001 R.J. Rusay
⇔ ⇔
BasesBases(continued)(continued)
WeakWeak bases have very bases have very little dissociation little dissociation (or reaction (or reaction with water), eg. methyl amine has <100% hydroxide with water), eg. methyl amine has <100% hydroxide ion in aqueous solution.ion in aqueous solution.
HH33CNHCNH22(aq) + H(aq) + H22O(l) O(l) H H33CNHCNH33++(aq) + OH(aq) + OH(aq)(aq)
Organic bases are weak bases; for example, Organic bases are weak bases; for example, dopamine (neurotransmitter), cadaverine (product of dopamine (neurotransmitter), cadaverine (product of cellular decomposition) and morphine (narcotic pain cellular decomposition) and morphine (narcotic pain killer) are weak bases.killer) are weak bases.
Strong or weak bases? Strong or weak bases?
Water as an Acid and a BaseWater as an Acid and a Base
Water is Water is amphotericamphoteric (it can behave (it can behave either as an acid or a base).either as an acid or a base).
HH22O + HO + H22O O H H33OO++ + OH + OH
conj conjconj conj acid 1 base 1 acid 2 base 2acid 1 base 1 acid 2 base 2
KKww = 1 = 1 10 101414 at 25°C at 25°C
Water: Self-ionizationWater: Self-ionization
The pH ScaleThe pH Scale pH pH log[Hlog[H++] ] log[Hlog[H33OO++] ]
pH in water ranges from 0 to 14.pH in water ranges from 0 to 14.
KKww = 1.00 = 1.00 10 101414 = [H = [H++] [OH] [OH]]
pKpKww = = 14.00 = pH + pOH14.00 = pH + pOH As pH rises, pOH falls (sum = 14.00).As pH rises, pOH falls (sum = 14.00).There are no theoretical limits on the values of pH or pOH. (e.g. pH of 2.0 M HCl is -0.301, the pH at Iron Mountain is ~ -2 to -3)
The pH of Some Familiar
Aqueous Solutions
[H3O+]
[OH-]
[OH-] = KW
[H3O+]
neutralsolution
acidicsolution
basicsolution
[H3O+]> [OH-]
[H3O+]< [OH-]
[H3O+] = [OH-]
Natural IndicatorsNatural Indicators
The pH ScaleThe pH Scale
1 1
1 1
1.0 1.0
12.0 12.0
1 x 101 x 10-11-11 3 3
1 x 101 x 10-4-44 4
1 x 101 x 10-1-1
Neutralization ReactionsNeutralization Reactions
Aqueous Reactions:Aqueous Reactions: NeutralizationNeutralization Net Ionic EquationsNet Ionic Equations
HCl(aq) + NaOH (aq) ---> NaCl (aq) + H2O(l) ___________________________________________________
HCl(aq) ---> H+(aq) + Cl -
(aq)
NaOH (aq) ---> Na+(aq)+ OH-
(aq)
NaCl (aq) ---> Na+(aq)+ Cl-
(aq) ________________________________________________
Na+(aq)+ OH-
(aq) + H+(aq) + Cl -
(aq) ---> Na+(aq)+
Cl-(aq) + H2O(l) _______________________________________________________
© Copyright 1995-2000 R.J. Rusay© Copyright 1995-2000 R.J. Rusay
H+(aq) + OH -
(aq) ---> H2O(l)
Acid-Base TitrationAcid-Base Titration
Acid-Base TitrationAcid-Base Titration
Stomach ChemistryStomach Chemistry
BuffersBuffers