Page 1 - 3. LESSON NOTE-(COMBINATION & DECOMPOSITION REACTION)
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SAI International School
Lesson Notes
Subject_Chemistry
Ch-Chemical Reactions and Equations
Topic-Types of Chemical Reactions
(Combination, Decomposition Reactions)
Module -2 Dt_20/3/2020
A combination reaction is a chemical reaction in two or more substances combine
together to produce a new compound.
A single substance as a product is the key characteristic of the combination
reaction.
For ex- 2 H 2(g) + O 2(g) → 2 H 2O(ℓ)
Most combination reactions are exothermic in nature. ... Combination reactions involve
the formation of new bonds and this process releases a large amount of energy in the form
of heat.
Ex-i)Burnig of Magnesium ribbon
2Mg+O2→2MgO+Heat
ii)Formation of slaked lime
CaO + H2O→Ca(OH)2+Heat
respiration considered an exothermic reaction:
➢ During respiration, glucose combines with oxygen in the cells of our body to form carbon
dioxide and water along with the production of energy.
Glucose + oxygen → carbon dioxide + water + energy
It is an exothermic reaction, because energy is produced during this process
Decomposition reaction
A single reactant decomposes on the application of heat or light or electricity to give two or more
products.
Decomposition reactions can be classified into three types:
• Thermal decomposition reaction.
• Electrolytic decomposition reaction.
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