HAVE A GREAT BREAK

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Announcements

• HAVE A GREAT BREAK!
• REMINDER NO LAB

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Types of Chemical Reactions

• Chapter 4 Goals
• To be able to predict chemical reactivity.
• To know how to synthesize specific compounds.

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Types of Reactions

• Acid-Base
• Oxidation-Reduction
• Precipitation
• Gas Forming
• Organic
• Substitution
• Addition
• Elimination

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Reactions in Aqueous Solution

• Aqueous- solvent is water
• Reactions well discuss today/next week are in
  aqueous solution, unless otherwise noted
• Acid-Base
• Redox
• Precipitation

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Electrolytes

• Strong All of the solute comes apart to yield
  ions in solution
• Dissolution of KMnO4
• Weak Some of the solute comes apart to yield
  ions
• Nonelectrolytes No ions formed
• Lets compare

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Electrolytes in the Human Body

• Most important
• Na, Cl-, K, Ca2, Mg2 ,HCO3-, and PO43-, SO42-
• Elevated K? cardiac arrythmia
• Decreased extracellular K? paralysis
• Excess extracellular Na? fluid retention
• Decreased plasma Ca2 and Mg2 ? muscle spasms

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Acids and Bases

• Theories- theres lots of them
• Ones well use in this course
• Lewis (later)
• Brønsted-Lowry (now)
• An acid is a substance that donates a proton (H)
  to a base
• The hydronium ion

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Brønsted-Lowry Definitions

• Acid donates a proton (H) to a base
• Base accepts a proton (H) from an acid
• Acid base reactions are reversible (almost always)

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Brønsted-Lowry Definitions

• Acid donates a proton (H) to a base
• Base accepts a proton (H) from an acid
• Acid base reactions are reversible (almost always)

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Important Acids and Bases
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Strong Acids

• 100 of acid molecules produce ions in water
• Dissociation vs. ionization

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Weak Acids

• Only a few acid molecules produce ions (5)
• Strong vs. Weak acid ionization

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Polyprotic Acids

• Polyprotic acids can donate more than one H
• Sulfuric acid
• Citric acid (C6H8O7) Not all Hs are acidic

H2SO4 ? H HSO4- HSO4- ? H SO42-
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Bases

• Strong bases are hydroxide salts
• For now, the only important weak base is NH3.

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If H3PO4 reacts as an acid, which of the
following can it not make?

• H4PO4
• H2PO4-
• HPO42-
• PO43-

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If C2O42- (oxalate ion) reacts in an acid-base
reaction, which of the following can it not make?

• H2C2O4
• HC2O4-
• 2 CO2

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Acid Base Reactions
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Acid Base Reactions

• Strong Acid Strong Base
• HCl(aq) NaOH(aq) ? NaCl(aq) H2O(l) acid
  base salt
  water
• What do we get if we mix
• HBr LiOH ?

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Acid Base Reactions

• Diprotic acids or bases
• H2SO4(aq) NaOH(aq) ?
• H2SO4(aq) Ba(OH)2(aq) ?
• HCl(aq) Ba(OH)2(aq) ?

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Acid-Base Reactions

• Diprotic Acids or Bases
• H2SO4(aq) NaOH(aq) ?
• H2SO4(aq) Ba(OH)2(aq) ?
• HCl(aq) Ba(OH)2(aq) ?

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Acid-Base Reactions

• Strong Acid Weak Base
• HCl(aq) NH3(aq) ? NH4Cl(aq)

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Acid-Base Reactions

• Weak Acid Strong Base
• HCN(aq) NaOH(aq) ? NaCN(aq) H2O(l) acid
  base salt
  water

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Net Ionic Equations

• HCl(aq) NaOH(aq) ? NaCl(aq) H2O(l)
• What really happens
• H(aq) OH-(aq) ? H2O(l)
• Sodium ion and chloride ion are spectator ions

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Reactions involving weak bases

• HCl(aq) NH3(aq) ? NH4(aq) Cl-(aq)
• Net-Ionic Equation
• NH3(aq) H(aq) ? NH4(aq)

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CH3CO2H(aq) NaOH(aq) ?

• 1. CH3CO2H2(aq) NaO(aq)
• 2. CH3CO2-(aq) H2O(l) Na(aq)
• 3. CH4(g) CO2(g) H2O(l)

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HCN(aq) NH3(aq) ?

• 1. NH4(aq) CN-(aq)
• 2. H2CN(aq) NH2-(aq)
• 3. C2N2(s) 3 H2(g)

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Solution Concentration Molarity

• Molarity moles solute per liter of solution
• 0.30 mol NH3 dissolved in 0.500 LConcentration
  
• Written like NH3 0.60 M

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pH Scale

• In pure water, a few molecules ionize to form
  H3O and OHH2O H2O ? OH H3O
• In acidic and basic solutions, these
  concentrations are not equalacidic H3O gt
  OHbasic OH gt H3Oneutral H3O
  OH

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pH Scale

• Measure how much H3O is in a solution using pH
• pH lt 7.0 acidic
• pH gt 7.0 basic
• pH 7.0 neutral
• Measure of H3O and OH concentration (moles per
  liter) in a solution
• As acidity increases, pH decreases

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pH Scale

• The pH scale is logarithmic100 102 log(102)
  210 101 log(101) 11 100 log(100)
  00.1 101 log(101) 10.01 102 log(102)
  2
• pH log H3O
• pH if H3O 105? 109? Acidic or basic?
• pH if H3O 0.000057 M?

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Finding H3O from pH

• H3O 10-pH
• What is H3O if pH 8.9?

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pH Quantitative Measure of Acidity

• Acidity is related to concentration of H (or
  H3O)
• pH -logH3O