1 - Synthesis/Decomposition Reactions

Synthesis Reaction

Two or more elements or compounds combine to form a new substance

In general:

A + B → AB

Synthesis Reactions are also called…

COMBINATION or ADDITION reactions

Decomposition Reactions

A compound breaks down into elements or other compounds

In general:

AB → A + B

Oxides

When an element combines with oxygen an oxide is formed

Metal Oxides

• metals react with oxygen to form metal oxides

• are always solids

• react in water to form BASIC solutions

• are also called basic oxides

Non-metal oxides

• non-metals react with oxygen to form non-metal oxides

• are often gases or liquids

• react in water to form acidic solutions

• are also called acidic oxides

Special case - chlorates (ClO₃ ⁻¹)

metal chlorate → metal chloride + oxygen

example: CuClO₃₍ₛ₎ → CuCl₍ₛ₎ + O₂₍ₛ₎

Special case - carbonate (CO₃⁻²)

Metal carbonate → metal oxide + carbon dioxide

example: Na₂CO₃₍ₛ₎ → Na₂O₍ₛ₎ + CO₂_(g)

Special case - acids (H_)

Oxyacid → non-metal oxide + water

example: H₃PO₄₍ₐᵩ₎ → H₂O₍ₗ₎ + PO₂_(g)

Special cases - bases (_OH)

Base → metal oxide + water

example: Ca(OH)₂₍ₐ₎ → H₂O₍ₗ₎ + CaO₍ₛ₎