Double Displacement (or Replacement) Reactions - PowerPoint PPT Presentation

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Double Displacement (or Replacement) Reactions

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Double Displacement (or Replacement) Reactions Also referred to as metathesis reaction The two compounds exchange ions to produce two new compounds. – PowerPoint PPT presentation

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Title: Double Displacement (or Replacement) Reactions


1
Double Displacement (or Replacement) Reactions
  • Also referred to as metathesis reaction
  • The two compounds exchange ions to produce two
    new compounds. It is easier to simply remember
    that the cations ( ions) exchange anions (-
    ions).
  • AB CD ? CB AD
  • NOTE always write the cation first then the
    anion.
  • Many reactions including precipitation and
    neutralization use the double displacement
    mechanism.

2
Double Displacement (or Replacement) Reactions
  • PREDICT THE PRODUCT BALANCE
  • 1. MgSO4 LiOH ? ___________
  • 2. Pb(NO3)2 Na2CO3 ? ____________
  • 3. HNO3 Ba(OH)2 ? ___________

Answers are on the next slide.
3
Double Displacement (or Replacement) Reactions
  • ANSWERS
  • 1. MgSO4 2 LiOH ? Mg(OH)2 Li2SO4
  • 2. Pb(NO3)2 Na2CO3 ? PbCO3 2 NaNO3
  • 3. 2 HNO3 Ba(OH)2 ? Ba(NO3)2 2 H2O

Exchange cations
4
PRECIPITATION REACTION
  • A reaction where an insoluble solid is formed
    during a reaction between two aqueous solutions.
  • (aq) (aq) ? (aq) (s)
  • 2KI(aq) Pb(NO3)2(aq) ? 2KNO3(aq) PbI2(s)
  • NEUTRALIZATION REACTION
  • A reaction between an acid and a base which
    results in the production of a salt and water.
  • HA BOH ? (metal/nonmetal) H2O
  • HNO3(aq) KOH(aq) ? KNO3(aq) H2O(l)

Exchange cations
5
Single Displacement (or Replacement) Reactions
  • One element reacts with a compound to produce a
    different element and a new compound.
  • A BC ? AC B
  • NOTE if the element is a metal, it will replace
    the cation.
  • A BC ? C BA
  • NOTE if the element is a nonmetal, it will
    replace the anion.
  • Many reduction-oxidation reactions use the
    single displacement mechanism.

6
Single Displacement (or Replacement) Reactions
  • PREDICT THE PRODUCT
  • 1. Ca HCl ?
  • 2. ZnBr2 I2 ?
  • 3. Cu AgNO3 ?

Answers are on the next slide.
7
Single Displacement (or Replacement) Reactions
  • ANSWERS
  • 1. Ca 2 HCl ? CaCl2 H2
  • 2. ZnBr2 I2 ? ZnI2 Br2
  • 3. Cu 2AgNO3 ? 2Ag Cu(NO3)2

8
Reduction-Oxidation Reactions
  • A reaction in which electrons are transferred
    from one species to another.
  • Oxidation means the loss of electrons
  • Reduction means the gain of electrons
  • Rusting is a redox reaction
  • 4Fe (s) 3O2 (g) ? 2Fe2O3 (s)
  • As a reactant Fe has a zero oxidation state but
    as a product (in Fe2O3) iron has a 3 oxidation
    state. Three electrons per atom had to be
    transferred (lost) in order for this to happen.
    Note that oxygen also changed from a zero
    oxidation state to a 2- oxidation state. Oxygen
    needed to gain 2 electrons per atom.

9
Reduction-Oxidation Reactions
  • Oxidation means the loss of electrons
  • Reduction means the gain of electrons
  • Electrochemistry involves redox Rx.
  • Cu(s) 2AgNO3(aq) ? 2Ag(s) Cu(NO3)2(aq)
  • The reactant Cu has a zero oxidation state (all
    elements have a zero oxidation state) but as a
    product, in Cu(NO3)2,the copper atom loses two
    electrons and has a 2 oxidation state. The
    other atom which acquired the electrons donated
    by copper is silver. As a reactant silver has a
    1 oxidation state then by gaining electrons from
    copper, the ions are turned into elemental silver
    with a zero oxidation state.
  • The net effect of this reaction has metallic
    copper being oxidized to copper ions and silver
    ions being reduced to silver metal.

10
COMBINATION REACTION
  • A reaction in which two or more substances
    combine to form a single product.
  • A B C ? ABC
  • CaO(s) SO2(g) ? CaSO3(s)
  • DECOMPOSITION REACTION
  • A reaction in which a single compound reacts to
    give two or more substances, usually requiring a
    raise in temperature.
  • ABC ? A B C
  • 2KClO3(s) ? 2KCl(s) 3O2(g)

11
COMBUSTION REACTION
  • A reaction of a substance with oxygen, usually
    the rapid release of heat produces a flame.
  • CH O2 ? CO2 H2O
  • 2C4H10(g) 13O2(g) ? 8CO2(g) 10H2O(g)
  • Many times in a combustion reaction, heat energy
    is given off. In chemical terms this is called
    an exothermic reaction. Thermochemistry is field
    of chemistry which studies the transfer of heat
    in a reaction.
  • The thermodynamic equation representing this
    exothermic reaction is
  • 2C4H10(g) 13O2(g) ? 8CO2(g) 10H2O(g)
    heat (in Joules)

12
GAS FORMATION REACTIONS
  • A reaction that produces a gas from reactants not
    in the gaseous state.
  • 2 HCl (aq) ZnS (s) ? ZnCl2 (aq) H2S (g)
  • Zn (s) 2 HCl (aq) ? ZnCl2 (aq) H2 (g)
  • Many gas formation reactions involve two steps,
    first the double displacement reaction then the
    decomposition reaction of an unstable substance.
  • Na2CO3 2HCl ? 2 NaCl H2CO3
  • H2CO3 ? CO2 H2O
  • Besides carbonic acid (H2CO3), sulfurous acid
    (H2SO3) also decomposes into SO2 and water.

13
PRACTICE PROBLEMS Write the following as
balanced chemical equations then classify each
reaction.
  • 1. Magnesium metal is combined with nitrogen at
    elevated temperatures to form magnesium nitride
    powder.
  • 2. An aqueous solution of soluble aluminum
    nitrate is mixed with aqueous sodium hydroxide to
    produce insoluble aluminum hydroxide and a sodium
    nitrate solution.
  • 3. Solid potassium sulfite is added to
    hydrochloric acid to produce sulfur dioxide,
    water, and potassium chloride.
  • 4. Acetic acid reacts with calcium hydroxide to
    produce calcium acetate and water.
  • 5. Lithium metal is dropped in water to produce
    lithium hydroxide and hydrogen gas.

3 Mg (s) N2 (g) ? Mg3N2 (s) combination, redox
Al(NO3)3 (aq) 3NaOH (aq) ? Al(OH)3(s)
3NaNO3(aq) ppt, DD
K2SO3 (s) 2HCl (aq) ? H2SO3 (aq) 2KCl (aq)
DD then H2SO3 (aq) ? H2O (l) SO2 (g)
decomposition overall Rx K2SO3 (s) 2HCl (aq)
? H2O (l) SO2 (g) 2KCl (aq)
2 HC2H3O2 (aq) Ca(OH)2 (aq) ? Ca(C2H3O2)2 (aq)
2H2O (l) DD, neutralization
2Li (s) 2H2O(l) ? 2LiOH (aq) H2 (g) SD, redox
14
GROUP STUDY PROBLEMSWrite the following as
balanced chemical equations then classify each
reaction.
  • 1. Solid mercuric oxide decomposes at high
    temperatures to form metallic mercury and oxygen.
  • 2. Aqueous lead(II) nitrate reacts with aqueous
    magnesium bromide to produce the insoluble salt
    lead(II)bromide and soluble magnesium nitrate.
  • 3. At room temperature, aqueous ammonium
    carbonate is added to hydrochloric acid to
    produce aqueous ammonium chloride, water and
    carbon dioxide.
  • 4. Hydrochloric acid is poured over tin metal
    producing hydrogen gas and tin (IV) chloride.
  • 5. The combustion of ethanol, C2H5OH, results in
    the production of carbon dioxide and water.
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