AcidBase Reactions: HCl example

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Acid-Base Reactions HCl example

• HCl (g) H2O (l) ? H3O (aq) Cl- (aq)
• HCl NaOH in water
• H3O (aq) Cl- (aq) Na (aq) OH- (aq) ?
• H2O (l) Cl- (aq) Na (aq) HOH
  (l)
• H3O (aq) OH- (aq) ? 2H2O (l)

Proton Transfer
Bronsted-Lowry Acids substances that donate a
proton Bronsted-Lowry Bases substances that
accept a proton
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What about weak acids?

• CH3COOH (aq) NaOH (aq) ? CH3COONa (aq) H2O
  (l)
• Total ionic?
• Net Ionic?
• Proton transfer occurs Ion appears undissociated

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Oxidation-Reduction Reactions

• Net movement of electrons from one reactant to
  another
• 2 Mg (s) O2 (g) --gt 2 MgO (s)
• Charge on magnesium? Oxygen?
• LEO GER
• Reducing agent? Oxidizing agent?

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Oxidation Numbers (O.N.)

• Any element has O.N. 0
• 1A(1) ions 1 2A(2) ions 2
• H ion can only be 1 or -1
• Oxygen only -2 (unless in peroxide or with F)
• Examples ZnCl2
• sulfur trioxide
• potassium permanganate

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Redox Reaction?

• CaO (s) CO2 (g) ? CaCO3 (s)
• Ca before 2 after 2
• O before 2- after 2-
• C before 4 after 4

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Balancing Redox Equations

• e- lost e- gained
• Oxidation Number Method
• Assign O.N.s
• Identify reduced and oxidized species
• Compute e- lost and gained
• Multiply so e- lost e- gained
• Complete balancing

Example PbS (s) O2 (g)
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Balancing Redox Equations

• Half-Reaction Method
• Assign O.N.s
• Write out each half reaction
• Multiply until e- lost e- gained
• Complete balancing

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Elements in Redox Reactions

• When an atom or molecule that starts as an
  element becomes part of a compound redox
  reaction
• Combination Reactions
• Decomposition Reactions
• Displacement Reactions

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Combination Reactions

• Metal nonmetal
• 4 Al (s) 3 O2 (g) ? 2 Al2O3 (s)
• Nonmetal nonmetal
• N2 (g) 3H2 (g) ? 2 NH3 (g)
• Compounds elements
• 2 NO (g) O2 (g) ? 2 NO2 (g)

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Decomposition Reactions

• Thermal Energy (Heat)
• 2 KClO3 (s) ? 2 KCl (s) 3 O2 (g)
• Electrical Energy (Electrolysis)
• 2 H2O (l) 2H2 (g) O2 (g)

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Displacement Reactions

• Double displacement
• Precipiatation
• Acid-base
• Single displacement
• Redox
• How do you know what will displace what?
• Activity Series (metals halogens)

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Activity Series of Metals

• Metal water ? metal hydroxide H2
• Metal metal halide

X-
X-
M
M
M
M


?
Strong reducing agent - more reactive
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Activity Series of Halogens

• F2 gt Cl2 gt Br2 gt I2

I2
I-
Cl2
Cl-
M
M

2
2

?
2
Strong oxidizing agent - more reactive
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Combustion Reactions

• Always redox O2 becomes O 2-
• O2 always a reactant
• H2O and CO2 common products

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Reversibility

• When it appears that no more product being made
  equilibrium
• Dynamic (not static)
• Example decomposition of CaCO3 (s)
• Weak acids/bases often at equilibrium