Combination Reaction

 Combination reactions are those reactions in which two or more reactants (elements and / or compounds) combine to produce a single product.

It means, no side product is formed during such reactions. Heat changes may take place during the reaction.

Activity – 5

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Examples of combination reactions

(a) between two elements

(b) between two compounds

(c) between an element and a compound

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Calcium oxide or quick lime reacts with water to give calcium hydroxide or slaked lime [Ca(OH)₂ ]. It is used for white washing walls. It reacts slowly with CO₂ in air and form a thin layer of calcium carbonate on the walls after 2 – 3 days of white washing and gives a shiny finish.

Ca(OH)₂ (aq) + CO₂ (g) →CaCO₃ (s) + H₂O(l)

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Which of the reaction is not a combination reaction ?

(a) CaO + H₂O → Ca(OH)₂

(b) CaO + CO₂ →  CaCO₃

(c) NH₃ + HCl →  NH₄Cl

(d) CaCO₃ → CaO + CO₂­

Define and give one example of combination reaction.

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Next –

Decomposition Reaction