Types of Reactions

Five Types of Reactions Synthesis Decomposition Single Replacement Double Replacement Combustion

1. Synthesis A + X a AX Mg + S a MgS 4 Fe + 3 O2 a 2 Fe2O3 Examples: Mg + S a MgS 4 Fe + 3 O2 a 2 Fe2O3 N2 + 3 H2 a 2 NH3 2 Na + S a Na2S Na+1S-2 2 Ca + O2 a 2 CaO Ca+2O-2 CaO NH3 + H2O a NH4OH Synthesis reactions can be recognized by 2 or more substances producing one.

2. Decomposition AX a A + X electricity 2 H2O a 2 H2 + O2 CaCO3 a CaO + CO2 D means heat 2 NH3 a N2 + 3 H2 NH3 a N2 + H2 Decomposition reactions can be recognized by 1 substance producing 2 or more.

3. Single Replacement AX + B a BX + A or AX + Y a AY + X If B is a metal, it will replace the metal, A AX + B a BX + A A X B If Y is a nonmetal, it will replace the nonmetal, X AX + Y a AY + X A X Y

Example: SrBr2 + Cl2 a SrCl2 + Br2 nonmetal 2 NaCl + F2 a 2 NaF + Cl2 Na+1F-1 + Cl2 Ca + ZnO a Zn + CaO metal Ca + a 2 H2O HOH Ca(OH)2 + H2 Ca+2OH-1 + H2 think of water as HOH metal

Some replacement reactions are not possible. In order for an element to be replaced, it has to be less active than the element that is replacing it. For example, the reaction Zn + CaCl2 a no reaction Zn is not more active than Ca. So it cannot replace it.

Activity Series for single replacement reactions Nonmetals Fluorine Lithium Potassium Barium Calcium Sodium Magnesium Aluminum Manganese Zinc Chromium Iron Cobalt Nickel Tin Lead Hydrogen Copper Silver Mercury Platinum Gold Nonmetals Fluorine Chlorine Bromine Zn + CaCl2 a no reaction decreasing activity Ca + ZnCl2 a CaCl2 + Zn

4. Double Replacement AX + BY a BX + AY 2 KI + Pb(NO3)2 a + PbI2 Pb+2I-1 K I Pb K+1 2 KNO3 KNO3 NO3 NO3-1 (balance the equation) (correct formulas) (switch places) (check the charges)

HCl + Mg(OH)2 a (switch places) HCl + Mg(OH)2 a MgCl + HOH check the charges HCl + Mg(OH)2 a Mg+2Cl-1 + H+1OH-1 correct formulas HCl + Mg(OH)2 a MgCl2 + HOH balance the equation 2HCl + Mg(OH)2 a MgCl2 + 2 HOH or 2 H2O

(switch places) FeS + HCl a FeS + HCl a FeCl + HS check the charges FeS + HCl a Fe+2Cl-1 + H+1S-2 correct formulas FeS + HCl a FeCl2 + H2S balance the equation FeS + 2 HCl a FeCl2 + H2S

5. Combustion of hydrocarbons CxHy + O2 a CO2 + H2O complete combustion CxHy + O2 a CO + H2O incomplete combustion Hydrocarbons are usually fuels. CH4 methane C3H8 propane (LP gas) C4H10 butane C8H18 octane (gasoline)

The reaction for the complete combustion of methane: CH4 + O2 a predict the products CH4 + O2 a CO2 + H2O balance the equation CH4 + O2 a CO2 + 2 H2O CH4 + 2 O2 a CO2 + 2 H2O

The reaction for the incomplete combustion of propane: C3H8 + O2 a CO + H2O balance the equation C3H8 + O2 a 3 CO + H2O C3H8 + O2 a 3 CO + 4 H2O 7 oxygens C3H8 + 3½ O2 a 3 CO + 4 H2O multiply by 2 2 C3H8 + 7 O2 a 6 CO + 8 H2O

5. Combustion of hydrocarbons 1. Synthesis A + X a AX 2. Decomposition AX a A + X 3. Single Replacement AX + B a BX + A or AX + Y a AY + X 4. Double Replacement AX + BY a BX + AY 5. Combustion of hydrocarbons CxHy + O2 a CO2 + H2O complete combustion CxHy + O2 a CO + H2O incomplete combustion