Combination Reactions:
In a combination reaction the atoms and/or molecules do what the name implies: they combine to form the product. Combination reactions are always exothermic. For example barium metal and fluorine gas will combine in a highly exothermic reaction to form the salt barium fluoride
A combination reaction can be of three types:
Type
Example
a) Between two elements C + O2 → CO2 Carbon completely burnt in oxygen yields carbon dioxide
b) Between two compounds 2CaO + 2H2O → 2Ca(OH)2 Calcium oxide (lime) combined with water gives calcium hydroxide (slaked lime)
c) Between an element and a compound O2 + 2H2O → 2H2O2 Oxygen (an element) combined with water (a compound) yields hydrogen peroxide
Type
Example
a) Between two elements C + O2 → CO2 Carbon completely burnt in oxygen yields carbon dioxide
b) Between two compounds 2CaO + 2H2O → 2Ca(OH)2 Calcium oxide (lime) combined with water gives calcium hydroxide (slaked lime)
c) Between an element and a compound O2 + 2H2O → 2H2O2 Oxygen (an element) combined with water (a compound) yields hydrogen peroxide
Examples:
Magnesium + Oxygen ---------------------------------- Magnesium Oxide
2Mg + O2 ---------------------------- 2MgO |
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Iron + Sulphur ------------------------------------------------- Iron Sulphide
Fe + S -------------------------------------------------- FeS |
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