{"id":626,"date":"2018-03-20T15:01:59","date_gmt":"2018-03-20T15:01:59","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/?post_type=chapter&p=626"},"modified":"2018-04-05T16:50:56","modified_gmt":"2018-04-05T16:50:56","slug":"5-4-some-types-of-chemical-reactions","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-orgbiochemistry\/chapter\/5-4-some-types-of-chemical-reactions\/","title":{"raw":"5.4 Some Types of Chemical Reactions","rendered":"5.4 Some Types of Chemical Reactions"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  1. Classify a given chemical reaction into a variety of types.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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    Although there are untold millions of possible chemical reactions, most can be classified into a small number of general reaction types. Classifying reactions has two purposes: it helps us to recognize similarities among them, and it enables us to predict the products of certain reactions. A particular reaction may fall into more than one of the categories that we will define in this book.<\/p>\r\n

    A combination (composition) reaction<\/span><\/span>\u00a0<\/strong>is a chemical reaction that makes a single substance from two or more reactants. There may be more than one molecule of product in the balanced chemical equation, but there is only one substance produced.<\/p>\r\n

    For example, the equation<\/p>\r\n4Fe + 3O2<\/sub> \u2192 2Fe2<\/sub>O3<\/sub><\/span><\/span>\r\n

    is a combination reaction that produces Fe2<\/sub>O3<\/sub> from its constituent elements\u2014Fe and O2<\/sub>. Combination reactions do not have to combine elements, however. The chemical equation<\/p>\r\nFe2<\/sub>O3<\/sub> + 3SO3<\/sub> \u2192 Fe2<\/sub>(SO4<\/sub>)3<\/sub><\/span><\/span>\r\n

    shows a combination reaction in which Fe2<\/sub>O3<\/sub> combines with three molecules of SO3<\/sub> to make Fe2<\/sub>(SO4<\/sub>)3<\/sub>.<\/p>\r\n\r\n

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    Example 3<\/h3>\r\n

    Which equations are combination reactions?<\/p>\r\n\r\n

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    1. Co(s) + Cl2<\/sub>(g) \u2192 CoCl2<\/sub>(s)<\/li>\r\n \t
    2. CO(g) + Cl2<\/sub>(g) \u2192 COCl2<\/sub>(g)<\/li>\r\n \t
    3. N2<\/sub>H4<\/sub>(\u2113) + O2<\/sub>(g) \u2192 N2<\/sub>(g) + 2H2<\/sub>O(\u2113)<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"786410\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"786410\"]\r\n
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      1. This is a combination reaction.<\/li>\r\n \t
      2. This is a combination reaction. (The compound COCl2 is called phosgene and, in the past, was used as a gassing agent in chemical warfare.)<\/li>\r\n \t
      3. This is not a combination reaction.[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n
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        Skill-Building Exercise<\/h3>\r\nWhich equations are combination reactions?\r\n
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        1. \r\n
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          P4<\/sub>(s) + 6Cl2<\/sub>(g) \u2192 4PCl3<\/sub>(g)<\/p>\r\n\r\n<\/div><\/li>\r\n \t

        2. \r\n
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          SO3<\/sub>(\u2113) + H2<\/sub>O(\u2113) \u2192 H2<\/sub>SO4<\/sub>(\u2113)<\/p>\r\n\r\n<\/div><\/li>\r\n \t

        3. \r\n
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          NaOH(s) + HCl(g) \u2192 NaCl(s) + H2<\/sub>O(\u2113)<\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n

          A decomposition reaction<\/strong>\u00a0<\/span><\/span>is the reverse of a combination reaction. In a decomposition reaction, a single substance is converted into two or more products. There may be more than one molecule of the reactant, but there is only one substance initially. For example, the equation<\/p>\r\n2NaHCO3<\/sub>(s) \u2192 Na2<\/sub>CO3<\/sub>(s) + CO2<\/sub>(g) + H2<\/sub>O(\u2113)<\/span><\/span>\r\n

          is a decomposition reaction that occurs when NaHCO3<\/sub> is exposed to heat. Another example is the decomposition of KClO3<\/sub>:<\/p>\r\n2KClO3<\/sub>(s) \u2192 2KCl(s) + 3O2<\/sub>(g)<\/span><\/span>\r\n

          This reaction was once commonly used to generate small amounts of oxygen in the chemistry lab.<\/p>\r\n\r\n

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          Note<\/h3>\r\n

          The decomposition reaction of NaHCO3<\/sub> is the reaction that occurs when baking soda is poured on a small kitchen fire. The intent is that the H2<\/sub>O and CO2<\/sub> produced by the decomposition will smother the flames.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n

          A combustion reaction<\/span><\/span><\/strong>\u00a0occurs when a substance combines with molecular oxygen to make oxygen-containing compounds of other elements in the reaction. One example is the burning of acetylene (C<\/span>2<\/sub>H<\/span>2<\/sub>) in torches:<\/span><\/p>\r\n\r\n<\/div>\r\n2C2<\/sub>H2<\/sub> + 5O2<\/sub> \u2192 4CO2<\/sub> + 2H2<\/sub>O<\/span><\/span>\r\n

          Oxygen (in its elemental form) is a crucial reactant in combustion reactions, and it is also present in the products.<\/p>\r\n\r\n

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          Note<\/h3>\r\n

          Energy in the form of heat is usually given off as a product in a combustion reaction as well.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n

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          Example 4<\/h3>\r\n

          Identify each type of reaction.<\/p>\r\n\r\n

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          1. 2K(s) + S(s) + 2O2<\/sub>(g) \u2192 K2<\/sub>SO4<\/sub>(s)<\/li>\r\n \t
          2. (NH4<\/sub>)2<\/sub>Cr2<\/sub>O7<\/sub>(s) \u2192 N2<\/sub>(g) + Cr2<\/sub>O3<\/sub>(s) + 4H2<\/sub>O(\u2113)<\/li>\r\n \t
          3. CH4<\/sub>(g) + 2O2<\/sub>(g) \u2192 CO2<\/sub>(g) + 2H2<\/sub>O(\u2113)<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"175956\"]Show Answer[\/reveal-answer]\r\n[hidden-answer a=\"175956\"]\r\n
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            1. Multiple reactants are combining to make a single product, so this reaction is a combination reaction.<\/li>\r\n \t
            2. A single substance reacts to make several products, so we have a decomposition reaction.<\/li>\r\n \t
            3. Oxygen reacts with a compound to make carbon dioxide (an oxide of carbon) and water (an oxide of hydrogen). This is a combustion reaction.[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n
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              Skill-Building Exercise<\/h3>\r\nIdentify each type of reaction.\r\n
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                C2<\/sub>H5<\/sub>OH + 3O2<\/sub> \u2192 2CO2<\/sub> + 3H2<\/sub>O<\/p>\r\n\r\n<\/div><\/li>\r\n \t

              2. \r\n
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                2Ca(s) + O2<\/sub>(g) \u2192 2CaO(s)<\/p>\r\n\r\n<\/div><\/li>\r\n \t

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                CaCO3<\/sub>(s) \u2192 CaO(s) + CO2<\/sub>(g)<\/p>\r\n\r\n<\/div><\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n

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                Concept Review Exercises<\/h3>\r\n
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                1. What is the difference between a combination reaction and a combustion reaction?<\/li>\r\n \t
                2. Give the distinguishing characteristic(s) of a decomposition reaction<\/li>\r\n \t
                3. How do we recognize a combustion reaction?<\/li>\r\n<\/ol>\r\n[reveal-answer q=\"296844\"]Show Answer[\/reveal-answer]\r\n\r\n<\/div>\r\n
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                  [hidden-answer a=\"296844\"]<\/p>\r\n\r\n

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                  1. A combination reaction produces a certain substance; a combustion reaction is a vigorous reaction, usually a combination with oxygen, that is accompanied by the production of light and\/or heat.<\/li>\r\n \t
                  2. In a decomposition reaction, a single substance reacts to make multiple substances as products.<\/li>\r\n \t
                  3. A combustion reaction is typically a vigorous reaction accompanied by light and\/or heat, usually because of reaction with oxygen.[\/hidden-answer]<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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                    Key Takeaway<\/h3>\r\n<\/div>\r\n
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