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Chemical Reaction A chemical reaction occurs when one or more chemicals react to become different chemicals. A chemical reaction is characterized by the re- arrangement of atoms from the reactant side of the equation to the product side. -: Example :- Hydrogen gas burns in oxygen to make water. 2H2 + O2 2H2O
Types of Chemical Reaction Decomposition Reactions Combination Reactions Single-Replacement Reactions Double-Replacement Reactions Combustion Reactions
Decomposition ReactionA decomposition reaction is a reaction in whicha single compound decomposes to two or moreother substances. AB A+B Where A and B can be elements or compounds.Most compounds can be broken down into simplersubstances or decomposed.
Decomposition Reaction -: Example :-The industrial preparation of calcium oxide (Lime)involves the decomposition of calcium carbonateby heating it. CaCO3(s) CaO(s) + CO2(g)
Combination ReactionA combination reaction is a reaction in whichtwo substances combine to form a third. A+B AB Where A and B can be elements or compounds.Decomposition and combination reactions canbe considered to be the reverse of each other.
Combination Reaction -: Example :-The reaction of calcium oxide with sulfur dioxideto form calcium sulfite CaO(s) + SO2(g) CaSO3(s)
Single-Replacement ReactionA single-replacement reaction is a reaction inwhich an element reacts with a compound andreplaces another element in the compound. A + BC AB + C Where A and C are elements and BC and AB are compounds.
Single-Replacement Reaction -: Example :-The reaction in which copper displaces silverfrom an aqueous solution of silver nitrateCu(s) + 2AgNO3(aq) Cu(NO3)2(aq) + 2Ag(s)
Double-Replacement ReactionA double-replacement reaction is a reaction inwhich there is an exchange of positive ions betweentwo compounds. These reactions generally takeplace between two ionic compounds in aqueoussolution. AB + CD AD + CB Where A and C are cations and B and D are anions.For a double-replacement reaction to occur, at leastone of the products must be a gas or water, or aprecipitate.
Double-Replacement Reaction -: Example :-Precipitation reactions are one type of double-replacement reaction.AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
Combustion Reaction A combustion reaction is a reaction in which a substance reacts with oxygen, usually with the fast release of heat and the production of a flame. Organic compounds usually burn in the oxygen in air to produce carbon dioxide and if the compound contains hydrogen, another product will be water. For example butane burns in air as follows.
Combustion Reaction -: Example :-In general: CxHy + O2 CO2 + H2OProducts in combustion are ALWAYS carbon dioxideAnd water.Combustion is used to heat homes and runautomobiles (octane, as in gasoline, is C8H18).