{"id":186,"date":"2018-02-10T13:00:26","date_gmt":"2018-02-10T18:00:26","guid":{"rendered":"http:\/\/kyantec.com\/?page_id=186"},"modified":"2018-05-22T10:39:54","modified_gmt":"2018-05-22T14:39:54","slug":"a-clock-reaction","status":"publish","type":"page","link":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/","title":{"rendered":"A Clock Reaction"},"content":{"rendered":"<h2>Summary<\/h2>\n<p>Two solutions (A and B) are mixed by pouring from one beaker into the other. After many seconds, the mixed solution turns dark blue, the color of the starch-iodine complex. Changing the concentration (or the temperature) of the solutions changes the time required for the blue color to be produced.<\/p>\n<h2>Materials<\/h2>\n<p><i>(wear safety equipment such as safety goggles)<\/i><\/p>\n<p><b>Solution A:<\/b>\u00a04.3 g of KIO<sub>3<\/sub>\u00a0(potassium iodate) per liter of water.<\/p>\n<p><b>Solution B:<\/b>\u00a0make a paste of 4 g of soluble starch in a small amount of warm water. Slowly add 800 mL of boiling water. Boil for a few minutes, then cool the solution. Add 0.2 g of Na<sub>2<\/sub>S<sub>2<\/sub>O<sub>5<\/sub>\u00a0(sodium metabisulfite). Add 5 mL of 1.0 M sulfuric acid (see tip 1). Dilute to 1 L.<\/p>\n<h2>Procedure<\/h2>\n<ol>\n<li>Place 50 mL of solution A in a 250 mL beaker.<\/li>\n<li>Place the same volume of solution B in a second beaker.<\/li>\n<li>Mix the two solutions by pouring from one beaker into the other twice, hold the filled beaker in your hands to better see the reaction.<\/li>\n<li>Note the time required for an observable reaction (blue color appearance) to occur after the solutions are mixed.<\/li>\n<li>The reaction time can be varied by diluting solution A or by operating at other temperatures until a maximum of 35<sup>o<\/sup>C (see tip 2).<\/li>\n<\/ol>\n<h2>Tips<\/h2>\n<ol>\n<li>After sulfuric acid is added, solution B is usable for the next 10-12 hours. If you need to keep the solution longer, add the acid just before using the solution.<\/li>\n<li>The starch-iodine complex becomes unstable above 50<sup>o<\/sup>C. Also, best results are obtained when the solutions are allowed to stabilize at room temperature for a minimum of a few hours prior to mixing.<\/li>\n<li>This experiment is a good example to illustrate the dependance of reaction rates on concentration and temperature. At room temperature, the reaction time ideally is 10-15 s. If the reaction is too slow, add more sodium metabisulfite or more acid to solution B. If the reaction is too fast, dilute solution A.<\/li>\n<li>The reaction mechanism can be summarized as follows:\n<ul>\n<li>Iodate reacts with bisulfite to form iodide (I<sup>&#8211;<\/sup>)<\/li>\n<li>Iodide reacts with Iodate to form Iodine (I<sub>2<\/sub>)<\/li>\n<li>Iodine is immediately consumed by reaction with bisulfite, giving back iodide.<\/li>\n<li>When all bisulfite has been used up, iodine interacts with starch to form a blue complex<\/li>\n<\/ul>\n<\/li>\n<li>Species such as I<sub>5<\/sub><sup>&#8211;<\/sup>\u00a0(equivalent to two iodines plus one iodide) and I<sub>3<\/sub><sup>&#8211;<\/sup>\u00a0(equivalent to one iodine plus one iodide) fitted inside the coiled amylose structure are responsible for the blue starch-iodine complex. Metabisulfite hydrolyzes to bisulfite (HSO<sub>3<\/sub><sup>&#8211;<\/sup>) in water solution.<\/li>\n<\/ol>\n<h2>Reference<\/h2>\n<p>L.R. Summerlin and J.L. Ealy, Jr., Chemical Demonstrations, A Sourcebook for Teachers, Vol.1, 2nd Edition, American Chemical Society, Washington (1988).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Summary Two solutions (A and B) are mixed by pouring from one beaker into the other. After many seconds, the mixed solution turns dark blue, the color of the starch-iodine complex. Changing the concentration (or the temperature) of the solutions changes the time required for the blue color to be produced. Materials (wear safety equipment [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":169,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-186","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>A Clock Reaction - Antec, Inc.<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"A Clock Reaction - Antec, Inc.\" \/>\n<meta property=\"og:description\" content=\"Summary Two solutions (A and B) are mixed by pouring from one beaker into the other. After many seconds, the mixed solution turns dark blue, the color of the starch-iodine complex. Changing the concentration (or the temperature) of the solutions changes the time required for the blue color to be produced. 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After many seconds, the mixed solution turns dark blue, the color of the starch-iodine complex. Changing the concentration (or the temperature) of the solutions changes the time required for the blue color to be produced. Materials (wear safety equipment [&hellip;]","og_url":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/","og_site_name":"Antec, Inc.","article_modified_time":"2018-05-22T14:39:54+00:00","twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/","url":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/","name":"A Clock Reaction - Antec, Inc.","isPartOf":{"@id":"https:\/\/staging.mswhost.com\/kyantec.com\/#website"},"datePublished":"2018-02-10T18:00:26+00:00","dateModified":"2018-05-22T14:39:54+00:00","breadcrumb":{"@id":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/a-clock-reaction\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/staging.mswhost.com\/kyantec.com\/"},{"@type":"ListItem","position":2,"name":"Tips &#038; Tricks","item":"https:\/\/staging.mswhost.com\/kyantec.com\/tips-tricks\/"},{"@type":"ListItem","position":3,"name":"A Clock Reaction"}]},{"@type":"WebSite","@id":"https:\/\/staging.mswhost.com\/kyantec.com\/#website","url":"https:\/\/staging.mswhost.com\/kyantec.com\/","name":"Antec, Inc.","description":"Chemicals, Lab Equipment, and Supplies","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/staging.mswhost.com\/kyantec.com\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"}]}},"_links":{"self":[{"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/pages\/186","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/comments?post=186"}],"version-history":[{"count":3,"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/pages\/186\/revisions"}],"predecessor-version":[{"id":2122,"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/pages\/186\/revisions\/2122"}],"up":[{"embeddable":true,"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/pages\/169"}],"wp:attachment":[{"href":"https:\/\/staging.mswhost.com\/kyantec.com\/wp-json\/wp\/v2\/media?parent=186"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}