# Synthesis and Decomposition reference ```LOOK AT YOUR EOC REFERENCE SHEETS IN THE FRONT OF YOUR 3-RING BINDER. YOU CAN USE THESE
PREDICT PRODUCTS!
Synthesis Reactions
Occurs when two or more substances combine to form a new compound
General Form:
A + B  AB
1. Formation of a Binary Compound
Reactions of elements with oxygen
Example:
2Mg (s) + O2 (g)  2MgO (s)
Reaction of two nonmetals
Example:
2H2 (g) + O2 (g)  2H2O (g)
S (s) + O2 (g)  SO2 (g)
Reactions of metals with nonmetals other than oxygen
Example:
2Na (s) + Cl2 (g)  2NaCl (s)
Co (s) + F2 (g)  CoF2 (s)
2. Metal oxide - water reactions
Example:
CaO (s) + H2O (l)  Ca(OH)2 (s)
- Active metals are highly reactive metals. Oxides of active metals
react with water to produce metal hydroxides.
3. Nonmetal oxide-water reactions
Example:
SO2 (g) + H2O (l)  H2SO3 (aq)
CO2 (g) + H2O (l)  H2CO3 (aq)
- Oxides of nonmetals from the upper right portion of the periodic
table react with water to produce acids.
A few things to notice:
- We start with more than one substance, but end up with only 1 compound.
- If we know the reactants we can predict the products using the criss-cross
method.
LOOK AT YOUR EOC REFERENCE SHEETS IN THE FRONT OF YOUR 3-RING BINDER. YOU CAN USE THESE
PREDICT PRODUCTS!
Decomposition Reactions
Occurs when a more complex substance breaks down into two simpler substances
General Form:
AB  A + B
1. Binary compounds
AB  A + B
Example: MgCl2 (s)  Mg (s) + Cl2 (g)
2. Metallic carbonates
MCO3  MO + CO2
Example: K2CO3 (s)  K2O (s) + CO2 (g)
3. Metallic hydrogen carbonates
MHCO3  MO + H2O + CO2
Example: Cu(HCO3)2 (s)  CuO (s) + H2O (l) + CO2 (g)
4. Metallic hydroxides
MOH  MO + H2O
Example: 2KOH (s)  K2O (s) + H2O (l)
5. Metallic chlorates
MClO3  MCl + O2
Example: 2KClO3 (s)  2KCl (s) + 3O2 (g)
6. Oxyacid (Ternary Acids) decompose to nonmetal oxides and water:
Acid  (NM)O + H2O
Example: H2SO4 (aq)
 SO3 (g) + H2O(l)
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