Section 1.14 Chemical Reactions  Page 53
a) decomposition reaction - a compound is broken down into two elements

b) synthesis reaction - two elements combine to form a compound

c)  decomposition reaction - a complex compound is broken down into two simpler compounds
  2 H2O(l) --> 2 H2(g) + O2(g)
A synthesis reaction is the combination of two or more simpler substances to form a more complex substance.  A combustion reaction is the rapid combination of oxygen and another element or compound to form new substances.  Thus, a combination reaction is a type of synthesis reaction where one of the reactants is oxygen.  For example,  4 Na(s)  +  O2(g) -->  2 Na2O(s) is a combustion reaction as well as a synthesis reaction.
a)   Zn(s)  +  CuCl2(aq) ----->  ZnCl2(aq) +  Cu(s)

b)   Ca(s)  +  2 HCl(aq)   ---->  CaCl2(s)  +  H2(g)

c)   2 Na(s)  +  2 H2O(l)   ------>  2 NaOH(aq)  +  H2(g)
In general, a synthesis reaction involves the reaction of two elements to form a new compound.  A decomposition reaction involves the breaking down of a compound into elements or simpler compounds.  A single displacement reaction is a reaction between an element and a compound.  A double displacement reaction occurs between two compounds.
The general equation for a synthesis reaction is  A  +  B  -->  AB, whereas the general equation for a decomposition reaction is AB  --->  A  +  B.  The decomposition reaction is the reverse of the synthesis reaction and vice versa.   They are therefore opposite reactions.
a)  Al(s)  +  3 AgNO3(aq)  --->  Al(NO3)3(aq)  + 3 Ag(s)    a single displacement reaction

b)  zinc  +  sulphuric acid ----->  zinc sulphate  + hydrogen gas
     Zn(s)  +  H2SO4(aq)  ----->  ZnSO4(aq)  +  H2(g)    a single displacement reaction

c)  aqueous magnesium chloride + aqueous silver nitrate --->  
                                                   solid silver chloride + aqueous magnesium nitrate
     MgCl2(aq)   + 2  AgNO3(aq)  ---->  2 AgCl(s)   +   Mg(NO3)2(aq)    a double displacement reaction

d)   sodium + water --->   sodium hydroxide and hydrogen gas
      2 Na(s)  + 2 H2O(l)   ---->  2 NaOH(aq)  + H2(g)   a single displacement reaction

e)   3 KOH(aq)   +  FeCl3(aq)  ----->   Fe(OH)3(ppt)  +  3 KCl(aq)  a double displacement reaction
a)   2 Li2O(s) --->  4 Li(s)  +  O2(g)
      2 MgO(s)  --->  2 Mg(s)  +  O2(g)
      ZnCl2(s)  --->  Zn(s)  +  Cl2(g)
a)  nitrogen monoxide decomposes into nitrogen and oxygen
     2 NO2(g) -----Pt/Pd----->   N2(g)  +  O2(g)

b)  Catalytic converters help to reduce the amounts of carbon monoxide, hydrocarbons, and nitrogen oxides in car exhaust, which are responsible for smog, acid rain, and pollution.  A catalytic converter is shaped like a honeycomb and is attached to a car's exhaust pipe.  It is coated with platinum and palladium, which act as catalysts (substances that speed up a chemical reaction but are recovered at the end) in the decomposition reactions of hydrocarbons to water and carbon monoxide, of carbon monoxide to carbon dioxide, and of nitrogen oxides to nitrogen and oxygen.  Since the products of these reactions do not contribute to air pollution, catalytic converters are effective tools in reducing air contaminants from cars.
a)  Student answers will vary depending on the metal they have chosen.  Copper is a metal that is rarely found in elemental form.  Most copper is mined as a carbonate or oxide ore.

b)   Copper carbonate and copper oxide are treated with dilute sulphuric acid to leach the copper out as copper(II) sulphate solution.  For copper oxide, the reaction is:
CuO(s)  +  H2SO4(aq)  ---->  CuSO4(aq)  +  H2O(l)

if the copper(II) sulphate solution reacts with iron, the copper is displaced, according to the following reaction equation:

CuSO4(aq)   +   Fe(s) ----->  FeSO4(aq)   +  Cu(s)

The copper has now be recovered in its elemental state.

c)   The types of reactions used to purify copper are a double displacement reaction
CuO(s)  +  H2SO4(aq)  ---->  CuSO4(aq)  +  H2O(l)

and a single displacement reaction
CuSO4(aq)   +   Fe(s) ----->  FeSO4(aq)   +  Cu(s)

d)  Copper mine tailings (leftover earth) are usually piled up or spread around a copper mine site.  These tailings have essentially no organic matter, are highly acidic, and represent an environmental threat from blowing dust, erosion, and runoff.  Also, if they run into bodies of water, they can cause damage to marine or freshwater ecosystems.