Chemical Reaction

Chemistry III

Composition/Combination/Synthesis It is a reaction takes place when two

or more elements combine to form more complex substance.

Gen. FormulaA + B AB

Combination

Metal + non metals Salt Mg 2 + Cl1 MgCl2

Cu + O2 CuO

Metal + Oxygen Metal Oxide Fe4 + O2 Fe2O4

Mg + O MgO

Combination

Metal oxide + Water Metal Hydroxide

Fe2O4 + H2O Fe(OH)4

Cu2O + H2O CuOH

Non-metal + Oxygen Non-metal oxide

C + O2 CO2

N3 + O2 N2O3

Combination

Non-metal oxide + Water Oxyacid

CO2 + H2O H2CO3

SO2 + H2O H2SO3

Metal Oxide + Non-metal Oxide salt

MgO + CO2 MgCO3

MgO + SO3 MgSO4

Decomposition

In decomposition reaction , one substance , usually undergoes a reaction to form two or more substances which may be elements or compound.This process usually requires heat to complete the reaction

AB A + B

Considerations

A. When an oxide is heated, generally oxygen is given off as one of the products.

1. HgO Hg + O2

2. KClO3 KCl + O2

Considerations

When nitrates are heated, it produces nitrites and oxygen.

KNO3 KN O2 + O2

Considerations

Some carbonates like limestone when heated, decompose to yield CO2.

CaCO3 CaO + CO2

MgCO3 MgO + CO2

Considerations

Some compounds such as baking soda ( sodium hydrogen carbonate or sodium bicarbonate ) when decompose will yield carbon dioxide, water and carbonate salt

2NaHCO3   Na2CO3+H2O +CO2

2KHCO3 K2CO3 +H2O +CO2

Considerations

Hydrates are substances that contain on e or more molecules of water for each formula units. These compounds, upon application of heat, readily decompose. The water is driven off leaving the anhydrous(without water) salt.

Na2CO3 + H2O Na2CO3

+H2O