{"id":7324,"date":"2021-06-08T21:55:43","date_gmt":"2021-06-08T21:55:43","guid":{"rendered":"https:\/\/opentextbc.ca\/introductorychemistry\/chapter\/types-of-chemical-reactions-single-and-double-displacement-reactions\/"},"modified":"2021-09-23T20:00:09","modified_gmt":"2021-09-23T20:00:09","slug":"types-of-chemical-reactions-single-and-double-displacement-reactions","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/introductorychemistry\/chapter\/types-of-chemical-reactions-single-and-double-displacement-reactions\/","title":{"raw":"Types of Chemical Reactions: Single- and Double-Displacement Reactions","rendered":"Types of Chemical Reactions: Single- and Double-Displacement Reactions"},"content":{"raw":"
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Learning Objectives<\/p>\r\n\r\n<\/header>\r\n

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  1. Recognize chemical reactions as single-replacement reactions and double-replacement reactions.<\/li>\r\n \t
  2. Use the periodic table, an activity series, or solubility rules to predict whether single-replacement reactions or double-replacement reactions will occur.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\nUp to now, we have presented chemical reactions as a topic, but we have not discussed how the products of a chemical reaction can be predicted. Here we will begin our study of certain types of chemical reactions that allow us to predict what the products of the reaction will be.\r\n\r\nA [pb_glossary id=\"8031\"]single-replacement reaction[\/pb_glossary]\u00a0is a chemical reaction in which one element is substituted for another element in a compound, generating a new element and a new compound as products. For example:\r\n

    2HCl(aq) +\u00a0Zn(s) \u2192\u00a0ZnCl2<\/sub>(aq) +\u00a0H2<\/sub>(g)<\/p>\r\nis an example of a single-replacement reaction. The hydrogen atoms in HCl are replaced by Zn atoms, and in the process a new element\u2014hydrogen\u2014is formed. Another example of a single-replacement reaction is:\r\n

    2NaCl(aq) + F2<\/sub>(g) \u2192\u00a02NaF(s) +\u00a0Cl2<\/sub>(g)<\/p>\r\nHere the negatively charged ion changes from chloride to fluoride. A typical characteristic of a single-replacement reaction is that there is one element as a reactant and another element as a product.\r\n\r\nNot all proposed single-replacement reactions will occur between two given reactants. This is most easily demonstrated with fluorine, chlorine, bromine, and iodine. Collectively, these elements are called the halogens<\/em> and are in the next-to-last column on the periodic table (see Figure 4.1 \"Halogens on the Periodic Table\"). The elements on top of the column will replace the elements below them on the periodic table but not the other way around. Thus, the reaction represented by:\r\n

    CaI2<\/sub>(s) +\u00a0Cl2<\/sub>(g) \u2192\u00a0CaCl2<\/sub>(s) +\u00a0I2<\/sub>(s)<\/p>\r\nThis reaction will occur, but the reaction\r\n

    CaF2<\/sub>(s) +\u00a0Br2<\/sub>(\u2113) \u2192\u00a0CaBr2<\/sub>(s) +\u00a0F2<\/sub>(g)<\/p>\r\nwill not because bromine is below fluorine on the periodic table. This is just one of many ways the periodic table helps us understand chemistry.\r\n\r\n[caption id=\"attachment_7322\" align=\"aligncenter\" width=\"600\"]\"Hydrogen, Figure 4.1 \"Halogens on the Periodic Table.\" The halogens are the elements in the next-to-last column on the periodic table.[\/caption]\r\n\r\n

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    Example 4.2<\/p>\r\n\r\n<\/header>\r\n

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    Problems<\/h1>\r\nWill a single-replacement reaction occur? If so, identify the products.\r\n
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    1. MgCl2<\/sub> + I2<\/sub> \u2192 ?<\/li>\r\n \t
    2. CaBr2<\/sub> + F2<\/sub> \u2192 ?<\/li>\r\n<\/ol>\r\n

      Solutions<\/h2>\r\n
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      1. Because iodine is below chlorine on the periodic table, a single-replacement reaction will not occur.<\/li>\r\n \t
      2. Because fluorine is above bromine on the periodic table, a single-replacement reaction will occur, and the products of the reaction will be CaF2<\/sub> and Br2<\/sub>.<\/li>\r\n<\/ol>\r\n

        Test Yourself<\/h1>\r\nWill a single-replacement reaction occur? If so, identify the products.\r\n

        FeI2<\/sub> + Cl2<\/sub> \u2192 ?<\/p>\r\n\r\n

        Answer<\/h2>\r\nYes; FeCl2<\/sub> and I2<\/sub>\r\n\r\n<\/div>\r\n<\/div>\r\nChemical reactivity trends are easy to predict when replacing anions in simple ionic compounds\u2014simply use their relative positions on the periodic table. However, when replacing the cations, the trends are not as straightforward. This is partly because there are so many elements that can form cations; an element in one column on the periodic table may replace another element nearby, or it may not. A list called the [pb_glossary id=\"8044\"]activity series[\/pb_glossary]\u00a0does the same thing the periodic table does for halogens: it lists the elements that will replace elements below them in single-replacement reactions. A simple activity series is shown below.\r\n
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        Activity Series for Cation Replacement in Single-Replacement Reactions<\/h1>\r\n