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Acid-Base Theories. And Much More. Arrhenius Theory. An Acid is a substance that produces H+ ions in solution. A base is a substance that produces OH- ions in solution. Neutralization occurs when H+ ions combine with OH- ions to form water. Acid or Base (Arrhenius Style). H 2 SO 4 - PowerPoint PPT Presentation
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Properties of Acids• Sour taste• Turn blue litmus red (and other indicators)• Neutralize bases• Conduct electricity (electrolytes)• React with active metals (group I, II) to produce H2 gas
• React with metal oxides to produce a salt of the metal and water
• Produce H+ or H3O+ in solution (see acid-base theories)
• pH less than 7
Properties of Bases
• Bitter taste ex. tonic water (quinine)• Turn red litmus blue (and other indicators)• Neutralize acids• Conduct electricity (electrolytes)• Feel slippery (soapy)• pH greater than 7• Produce OH- in solution
Arrhenius Theory
An Acid is a substance that produces H+ ions in solution.
A base is a substance that produces OH- ions in solution.
Neutralization occurs when H+ ions combine with OH- ions to form water.
)()()(: 2 lOHaqOHaqHequationionicNet
)()()()( 2 aqNaCllOHaqNaOHaqHCl
)()()()( 2 aqNaCllOHaqNaOHaqHCl
Limitations of Arrhenius Theory
• Acids (like HCl) are able to be neutralized by NaOH and NH3.
• Not all bases have OH- ions, NH3 in H2O does, but, if NH3 reacts as a gas with HCl gas, NH4Cl is still formed, but is not a solution, so this theory won’t always work.
)()()(
)()()()(
43
2
aqClNHaqHClaqNH
lOHaqNaClaqNaOHaqHCl
Bronsted-Lowry Theory
• An acid is a proton donor.• A base is a proton acceptor.
ClOHHClOH 32
H3O+ is a hydronium ion (aka. THE
PROTON)
HCl is the acid
H2O is the base.
Conjugate Acid-Base Pairs
A conjugate acid is the substance that hasaccepted the proton (gained an H+)A conjugate base is the substance that has lostthe proton.Each acid has a conjugate base and each basehas a conjugate acid.
Formation of Acids
• Acids are formed when a non-metal oxide is dissolved in water (forms an oxyacid)
SO2 + H2O H2SO3
Formation of Bases
• Formed when a metal oxide reacts with water (forms a strong base)
Na2O + H2O 2NaOH
Strong Acids & Bases
• Strong acids – hydrogen halides, oxyacids of halogens, sulfuric acid & nitric acid
• Strong bases – NaOH, KOH, Cs(OH)2, Ca(OH)2
• Both of these ionize completely in H2O.
OHNaNaOH
ClOHOHHCl 32
Weak Acids & Bases
• Weak acids and bases do not ionize completely in water
• A weak acid/base will be shown with a double arrow reaction, and also have small Ka and Kb values
Ionization Constants
Acid ionization constant (Ka)• Magnitude dictates the
strength of the acid• Strong acids have large Ka
values – this means that they dissociate completely (100%)
• Weak acids have small Ka values – and do not dissociate completely (usually 5% or so)
Base ionization constant (Kb)• Magnitude dictates the
strength of the base• Strong bases have large Kb
values – and dissociate completely (100%)
• Weak bases have small Kb values - and do not dissociate completely (5% or so)
Ion Product of Water (Kw)
Kw = 1.0 x 10-14=[H+][OH-] – changes with temperature
Kw = Ka x Kb- Uses: Can find concentration of OH- or H+, the
Kb of the conjugate base (and vice versa), or used with pH or pOH calculations when necessary
pH and pOH
pH = -log10[H+] or pH = -log10[H3O+] (same thing)
[H+] = 10-pH
pOH = -log10[OH-]
[OH-] = 10-pOH
Equilibrium Problems Using Acids
Type 1: Solving for KaYou must have the following:
- the equation for the reaction- the equilibrium expression- the concentrations at equilibrium (ICE chart)
- The concentrations at equilibrium are usually found with pH or a % ionization.