Tuesday, October 25, 2011

3rd Quarter: Completing Chemical Reactions

COMPLETING CHEMICAL REACTIONS

 COMBINATION REACTIONS:    A  +  B   →   AB
The substance formed after a combination reaction can be predicted using the following:
1.       metal  +  nonmetal →  binary compound (oxide, sulfide, halide, etc.)
4 Al  +  3 O2  →  2 Al2O3
2.       nonmetal  +  oxygen  →  nonmetal oxide
C  +  O2  →  CO2  (in excess oxygen)
3.       metal oxide  +  water  →  metal hydroxide
CaO  +  H2O  →  Ca(OH)2
4.       nonmetal oxide  +  water  →  oxyacid
SO2  +  H2O  →  H2SO3
5.       metal oxide  +  nonmetal oxide  →  salt
CaO  +  SO2  →  CaSO3
6.       ammonia  +  acid  →  ammonium salt
NH3  +  HCl  →  NH4Cl

DECOMPOSITION REACTIONS:    AB  → A  + B   
  1. Hydrates when heated, decompose to yield water and the anhydrous salt.
BaCl2 Ÿ 2 H2O → BaCl2  +  H2O
  1. Chlorates, when heated, decompose to form chlorides plus and oxygen gas.
2 KClO3  →  2 KCl  +  3 O2
  1. A few metal oxides decompose when heated to form the free metal and oxygen gas.
2 HgO  →  2 Hg  +  O2
  1. Most carbonates, when heated, decompose to form oxide and carbon dioxide.
CaCO3  →  CaO  +  O2
  1. Most hydrogen carbonates (bicarbonates) when heated, decompose to form an oxide plus water and carbon dioxide.
Ca(HCO3)2  →  CaO  +  H2O  +  CO2
(Note that IA carbonates are stable toward heat, other carbonates are not.)
2 NaHCO3  →  Na2CO3  +  H2O  +  CO2
  1. Some acids, when heated, decompose into water and nonmetallic oxides.
H2CO3  →  H2O  +  CO2
  1. Many metallic hydroxides, when heated, decompose into metallic oxides and water.
Ca(OH)2  →  CaO  +  H2O
  1. Some decomposition reactions are produced by an electric current.
2 H2O  →  2 H2  +  O2
  1. Some nitrates, when heated, decompose into metallic nitrites and oxygen gas.
2 KNO3  →  2 KNO2  +  O2

Single Replacement Reactions:    A  +  BC  →  B  +  AC

Activity Series of Metals -  Li, K, Ba, Sr, Ca, Na, Mg, Al, Mn, Zn, Fe, Cd, Co, Ni, Sn, Pb, H, Cu, Ag, Hg, Au
Nonmetals (halogens) -  F2, Cl2, Br2, I2
1.       Replacement of a metal in a compound by a more active metal
Zn  +  CuSO4    →  ZnSO4  +  Cu
2.       Replacement of hydrogen in water by metals
Ca   +  2 H2O  →   Ca(OH)2   +  H2
3.       Replacement of Hydrogen in acids by metals
Mg  +  H2SO4  →   MgSO4   +  H2
4.       Replacement of halogens
Cl2   +  2 KBr   →   2 KCl   +  Br2      

 

Double Replacement Reactions:    AB  +  CD   →  CB   +  AD

1.       A salt and a base
Ca(NO3)2  +  2 NaOH  → 2  NaNO3  +   Ca(OH)2
2.       Two salts
2 KCl   +   Pb (NO3)2   →    PbCl2   +   2 KNO3
3.       A salt and an acid
Ba(NO3)2  +   H2SO4   →    BaSO4   +   2 HNO3
4.       Metal carbonate and an acid
MgCO3   +    2 HCl   →     MgCl2   +   H2O   +  CO2
5.       An acid and a base (neutralization reaction)
2 HCl +   Mg(OH)2    →   MgCl2   +  2 H2O
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