{"id":3677,"date":"2019-04-23T12:56:48","date_gmt":"2019-04-23T12:56:48","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/chapter\/factors-that-affect-the-rate-of-reactions-2\/"},"modified":"2019-04-29T13:25:58","modified_gmt":"2019-04-29T13:25:58","slug":"factors-that-affect-the-rate-of-reactions-2","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/chapter\/factors-that-affect-the-rate-of-reactions-2\/","title":{"raw":"Factors that Affect the Rate of Reactions","rendered":"Factors that Affect the Rate of Reactions"},"content":{"raw":"<div class=\"bcc-box bcc-highlight\">\r\n<h3>Learning Objectives<\/h3>\r\n<ul>\r\n \t<li>To gain an understanding of collision theory.<\/li>\r\n \t<li>To gain an understanding of the four main factors that affect reaction rate.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<em>Reaction kinetics<\/em> is the study of the rate of chemical reactions, and reaction rates can vary greatly over a large range of time scales. Some reactions can proceed at explosively fast rates like the detonation of fireworks (Figure 17.1 \"<span class=\"Apple-style-span\">Fireworks at Night Over River\"<\/span>), while others can occur at a sluggish rate over many years like the rusting of barbed wire exposed to the elements (Figure 17.2 \"<span class=\"Apple-style-span\">Rusted Barbed Wire\"<\/span>).\r\n\r\nFigure 17.1. Fireworks at Night Over River\r\n\r\n<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Fireworks_at_night_over_river.jpg\"><img class=\"alignnone wp-image-1182\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125635\/Fireworks_at_night_over_river-1.jpg\" alt=\"Figure 17.1-1. Fireworks at night over river\" width=\"400\" height=\"534\" \/><\/a>\r\n\r\nThe chemical reaction in fireworks happens at an explosive rate.[footnote]Fireworks at night over river by Jon Sullivan\/Public Domain [\/footnote]\r\n\r\n<span class=\"Apple-style-span\">Figure 17.2. Rusted Barbed Wire<\/span>\r\n\r\n<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/barbed-wire.jpg\"><img class=\"alignnone wp-image-1183\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125639\/barbed-wire-1.jpg\" alt=\"Figure 17.1-2. Rusted Barbed Wire\" width=\"400\" height=\"300\" \/><\/a>\r\n\r\nThe rusting of barbed wire occurs over many years.[footnote]Barbed wire (after years of hard work) by Waugsberg\/<a title=\"CC-BY-SA 3.0\" href=\"http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/deed.en\" target=\"_blank\" rel=\"noopener\">CC-BY-SA 3.0<\/a>[\/footnote]\r\n<h2>Collision Theory<\/h2>\r\nTo understand the kinetics of chemical reactions, and the factors that affect kinetics, we should first examine what happens during a reaction on the molecular level. According to the <b>collision theory <\/b>of reactivity, reactions occur when reactant molecules \u201ceffectively collide.\u201d For an \u201ceffective collision\u201d to occur, the reactant molecules must be oriented in space correctly to facilitate the breaking and forming of bonds and the rearrangement of atoms that\u00a0result in the formation of product molecules (Figure 17.3 \"Collision Visualizations<span class=\"Apple-style-span\">\"<\/span>).\r\n\r\n<span class=\"Apple-style-span\">Figure 17.3. Collision Visualizations<\/span>\r\n\r\n<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Effective-collision.jpg\"><img class=\"alignnone wp-image-1260 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125642\/Effective-collision-1.jpg\" alt=\"Figure 17.1-3. Visualization of an ineffective and effective collision based on molecular orientation.\" width=\"514\" height=\"257\" \/><\/a>\r\n\r\n<span class=\"Apple-style-span\">This visualization shows\u00a0an ineffective and effective collision based on molecular orientation.<\/span>\r\n\r\nDuring a molecular collision, molecules must also possess a minimum amount of kinetic energy for an effective collision to occur. This energy varies for each reaction, and is known as the <b>activation energy (<em>E<\/em><sub>a<\/sub>) <\/b>(Figure 17.4 \"<span class=\"Apple-style-span\">Potential Energy and\u00a0Activation Energy<\/span>\"). The rate of reaction therefore depends on the activation energy; a higher activation energy means that fewer\u00a0molecules will have sufficient energy to undergo an effective collision.\r\n\r\n<span class=\"Apple-style-span\">Figure 17.4. Potential\u00a0Energy and\u00a0Activation\u00a0Energy<\/span>\r\n\r\n[caption id=\"attachment_1258\" align=\"alignnone\" width=\"363\"]<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/activation-energy-1.jpg\"><img class=\"wp-image-1258 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125645\/activation-energy-1-1.jpg\" alt=\"Figure 17.1-4. Potential energy diagram for a hypothetical reaction.\" width=\"363\" height=\"261\" \/><\/a> This potential energy diagram shows the activation energy of a hypothetical reaction.[\/caption]\r\n<h2>Factors That Affect Rate<\/h2>\r\nThere are four main factors that can affect the reaction rate of a chemical reaction:\r\n\r\n1. <b>Reactant concentration.<\/b> Increasing the concentration of one or more reactants will often increase the rate of reaction. This occurs because a higher concentration of a reactant will lead to more collisions of that reactant in a specific time period.\r\n\r\n2. <b>Physical state of the reactants and surface area. <\/b>If reactant molecules exist in different phases, as in a heterogeneous mixture, the rate of reaction will be limited by the surface area of the phases that\u00a0are in contact. For example, if a solid metal reactant and gas reactant are mixed, only the molecules present on the surface of the metal are able to collide with the gas molecules. Therefore, increasing the surface area of the metal by pounding it flat or cutting it into many pieces will increase its reaction rate.\r\n\r\n3. <b>Temperature<\/b>. An increase in temperature typically increases the rate of reaction. An increase in temperature will raise the average kinetic energy of the reactant molecules. Therefore, a greater proportion of molecules will have the minimum energy necessary for an effective collision (Figure. 17.5 \"Temperature and\u00a0Reaction Rate\").\r\n\r\nFigure. 17.5 Temperature and\u00a0Reaction Rate\r\n\r\n[caption id=\"attachment_1262\" align=\"alignnone\" width=\"334\"]<a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Temperature-and-Kinetic-Energy-Distribution.jpg\"><img class=\"wp-image-1262 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125647\/Temperature-and-Kinetic-Energy-Distribution-1.jpg\" alt=\"Figure 17.1-4. Effect of temperature on the kinetic energy distribution of molecules in a sample.\" width=\"334\" height=\"287\" \/><\/a> Effect of temperature on the kinetic energy distribution of molecules in a sample[\/caption]\r\n\r\n4. <b>Presence of a catalyst<\/b>. A <b>catalyst<\/b> is a substance that accelerates a reaction by participating in it without being consumed. Catalysts provide an alternate reaction pathway to obtain products. They are critical to many biochemical reactions. They will be examined further in the section \"Catalysis.\"\r\n<div class=\"bcc-box bcc-success\">\r\n<h3>Key Takeaways<\/h3>\r\n<ul>\r\n \t<li>Reactions occur when two reactant molecules effectively collide, each having minimum\u00a0energy and correct orientation.<\/li>\r\n \t<li>Reactant concentration, the physical state of the reactants, and surface area, temperature, and the presence of a catalyst are the four main factors that affect reaction rate.<\/li>\r\n<\/ul>\r\n<\/div>","rendered":"<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\n<ul>\n<li>To gain an understanding of collision theory.<\/li>\n<li>To gain an understanding of the four main factors that affect reaction rate.<\/li>\n<\/ul>\n<\/div>\n<p><em>Reaction kinetics<\/em> is the study of the rate of chemical reactions, and reaction rates can vary greatly over a large range of time scales. Some reactions can proceed at explosively fast rates like the detonation of fireworks (Figure 17.1 &#8220;<span class=\"Apple-style-span\">Fireworks at Night Over River&#8221;<\/span>), while others can occur at a sluggish rate over many years like the rusting of barbed wire exposed to the elements (Figure 17.2 &#8220;<span class=\"Apple-style-span\">Rusted Barbed Wire&#8221;<\/span>).<\/p>\n<p>Figure 17.1. Fireworks at Night Over River<\/p>\n<p><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Fireworks_at_night_over_river.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1182\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125635\/Fireworks_at_night_over_river-1.jpg\" alt=\"Figure 17.1-1. Fireworks at night over river\" width=\"400\" height=\"534\" \/><\/a><\/p>\n<p>The chemical reaction in fireworks happens at an explosive rate.<a class=\"footnote\" title=\"Fireworks at night over river by Jon Sullivan\/Public Domain\" id=\"return-footnote-3677-1\" href=\"#footnote-3677-1\" aria-label=\"Footnote 1\"><sup class=\"footnote\">[1]<\/sup><\/a><\/p>\n<p><span class=\"Apple-style-span\">Figure 17.2. Rusted Barbed Wire<\/span><\/p>\n<p><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/barbed-wire.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1183\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125639\/barbed-wire-1.jpg\" alt=\"Figure 17.1-2. Rusted Barbed Wire\" width=\"400\" height=\"300\" \/><\/a><\/p>\n<p>The rusting of barbed wire occurs over many years.<a class=\"footnote\" title=\"Barbed wire (after years of hard work) by Waugsberg\/CC-BY-SA 3.0\" id=\"return-footnote-3677-2\" href=\"#footnote-3677-2\" aria-label=\"Footnote 2\"><sup class=\"footnote\">[2]<\/sup><\/a><\/p>\n<h2>Collision Theory<\/h2>\n<p>To understand the kinetics of chemical reactions, and the factors that affect kinetics, we should first examine what happens during a reaction on the molecular level. According to the <b>collision theory <\/b>of reactivity, reactions occur when reactant molecules \u201ceffectively collide.\u201d For an \u201ceffective collision\u201d to occur, the reactant molecules must be oriented in space correctly to facilitate the breaking and forming of bonds and the rearrangement of atoms that\u00a0result in the formation of product molecules (Figure 17.3 &#8220;Collision Visualizations<span class=\"Apple-style-span\">&#8220;<\/span>).<\/p>\n<p><span class=\"Apple-style-span\">Figure 17.3. Collision Visualizations<\/span><\/p>\n<p><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Effective-collision.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1260 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125642\/Effective-collision-1.jpg\" alt=\"Figure 17.1-3. Visualization of an ineffective and effective collision based on molecular orientation.\" width=\"514\" height=\"257\" \/><\/a><\/p>\n<p><span class=\"Apple-style-span\">This visualization shows\u00a0an ineffective and effective collision based on molecular orientation.<\/span><\/p>\n<p>During a molecular collision, molecules must also possess a minimum amount of kinetic energy for an effective collision to occur. This energy varies for each reaction, and is known as the <b>activation energy (<em>E<\/em><sub>a<\/sub>) <\/b>(Figure 17.4 &#8220;<span class=\"Apple-style-span\">Potential Energy and\u00a0Activation Energy<\/span>&#8220;). The rate of reaction therefore depends on the activation energy; a higher activation energy means that fewer\u00a0molecules will have sufficient energy to undergo an effective collision.<\/p>\n<p><span class=\"Apple-style-span\">Figure 17.4. Potential\u00a0Energy and\u00a0Activation\u00a0Energy<\/span><\/p>\n<div id=\"attachment_1258\" style=\"width: 373px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/activation-energy-1.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1258\" class=\"wp-image-1258 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125645\/activation-energy-1-1.jpg\" alt=\"Figure 17.1-4. Potential energy diagram for a hypothetical reaction.\" width=\"363\" height=\"261\" \/><\/a><\/p>\n<p id=\"caption-attachment-1258\" class=\"wp-caption-text\">This potential energy diagram shows the activation energy of a hypothetical reaction.<\/p>\n<\/div>\n<h2>Factors That Affect Rate<\/h2>\n<p>There are four main factors that can affect the reaction rate of a chemical reaction:<\/p>\n<p>1. <b>Reactant concentration.<\/b> Increasing the concentration of one or more reactants will often increase the rate of reaction. This occurs because a higher concentration of a reactant will lead to more collisions of that reactant in a specific time period.<\/p>\n<p>2. <b>Physical state of the reactants and surface area. <\/b>If reactant molecules exist in different phases, as in a heterogeneous mixture, the rate of reaction will be limited by the surface area of the phases that\u00a0are in contact. For example, if a solid metal reactant and gas reactant are mixed, only the molecules present on the surface of the metal are able to collide with the gas molecules. Therefore, increasing the surface area of the metal by pounding it flat or cutting it into many pieces will increase its reaction rate.<\/p>\n<p>3. <b>Temperature<\/b>. An increase in temperature typically increases the rate of reaction. An increase in temperature will raise the average kinetic energy of the reactant molecules. Therefore, a greater proportion of molecules will have the minimum energy necessary for an effective collision (Figure. 17.5 &#8220;Temperature and\u00a0Reaction Rate&#8221;).<\/p>\n<p>Figure. 17.5 Temperature and\u00a0Reaction Rate<\/p>\n<div id=\"attachment_1262\" style=\"width: 344px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/opentextbc.ca\/introductorychemistry\/wp-content\/uploads\/sites\/17\/2014\/05\/Temperature-and-Kinetic-Energy-Distribution.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1262\" class=\"wp-image-1262 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/4084\/2019\/04\/23125647\/Temperature-and-Kinetic-Energy-Distribution-1.jpg\" alt=\"Figure 17.1-4. Effect of temperature on the kinetic energy distribution of molecules in a sample.\" width=\"334\" height=\"287\" \/><\/a><\/p>\n<p id=\"caption-attachment-1262\" class=\"wp-caption-text\">Effect of temperature on the kinetic energy distribution of molecules in a sample<\/p>\n<\/div>\n<p>4. <b>Presence of a catalyst<\/b>. A <b>catalyst<\/b> is a substance that accelerates a reaction by participating in it without being consumed. Catalysts provide an alternate reaction pathway to obtain products. They are critical to many biochemical reactions. They will be examined further in the section &#8220;Catalysis.&#8221;<\/p>\n<div class=\"bcc-box bcc-success\">\n<h3>Key Takeaways<\/h3>\n<ul>\n<li>Reactions occur when two reactant molecules effectively collide, each having minimum\u00a0energy and correct orientation.<\/li>\n<li>Reactant concentration, the physical state of the reactants, and surface area, temperature, and the presence of a catalyst are the four main factors that affect reaction rate.<\/li>\n<\/ul>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-3677\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li><strong>Authored by<\/strong>: Jessie A. Key. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/opentextbc.ca\/introductorychemistry\/\">https:\/\/opentextbc.ca\/introductorychemistry\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA: Attribution-NonCommercial-ShareAlike<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section><hr class=\"before-footnotes clear\" \/><div class=\"footnotes\"><ol><li id=\"footnote-3677-1\">Fireworks at night over river by Jon Sullivan\/Public Domain  <a href=\"#return-footnote-3677-1\" class=\"return-footnote\" aria-label=\"Return to footnote 1\">&crarr;<\/a><\/li><li id=\"footnote-3677-2\">Barbed wire (after years of hard work) by Waugsberg\/<a title=\"CC-BY-SA 3.0\" href=\"http:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/deed.en\" target=\"_blank\" rel=\"noopener\">CC-BY-SA 3.0<\/a> <a href=\"#return-footnote-3677-2\" class=\"return-footnote\" aria-label=\"Return to footnote 2\">&crarr;<\/a><\/li><\/ol><\/div>","protected":false},"author":89971,"menu_order":2,"template":"","meta":{"_candela_citation":"[{\"type\":\"original\",\"description\":\"\",\"author\":\"Jessie A. Key\",\"organization\":\"\",\"url\":\"https:\/\/opentextbc.ca\/introductorychemistry\/\",\"project\":\"\",\"license\":\"cc-by-nc-sa\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["jessie-a-key"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[59],"license":[50],"class_list":["post-3677","chapter","type-chapter","status-publish","hentry","contributor-jessie-a-key","license-cc-by"],"part":3670,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapters\/3677","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/wp\/v2\/users\/89971"}],"version-history":[{"count":2,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapters\/3677\/revisions"}],"predecessor-version":[{"id":3881,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapters\/3677\/revisions\/3881"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/parts\/3670"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapters\/3677\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/wp\/v2\/media?parent=3677"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/pressbooks\/v2\/chapter-type?post=3677"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/wp\/v2\/contributor?post=3677"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-introductorychemistry\/wp-json\/wp\/v2\/license?post=3677"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}