{"id":2824,"date":"2016-08-24T19:44:26","date_gmt":"2016-08-24T19:44:26","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/?post_type=chapter&#038;p=2824"},"modified":"2016-08-24T22:45:35","modified_gmt":"2016-08-24T22:45:35","slug":"indicators","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/chapter\/indicators\/","title":{"raw":"Indicators","rendered":"Indicators"},"content":{"raw":"<div class=\"x-ck12-data-objectives\">\r\n<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\n<ul>\r\n \t<li>Define indicator.<\/li>\r\n \t<li>Describe the use of indicators in acid-base experiments.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox examples\">\r\n<h3><strong>Who would write a song about a cabbage? <\/strong><\/h3>\r\n<p id=\"x-ck12-ZWRhYTE5MTU2YmExZDhjYmE3OTM5NGVlZTU1MDdjOGM.-qtk\">There\u2019s an old bluegrass song known as \u201cBoil Them Cabbage Down\u201d (<a href=\"http:\/\/www.youtube.com\/watch?v=xT9TTlh5jgA\" target=\"_blank\">check out this great performance<\/a>). Many people enjoy the music, but chemistry students also enjoy the product of the boiled cabbage. Extracting the anthocyanin dye from cabbage leaves with boiling water gives a solution that is red when acidic, purple when neutral, and green to yellow when basic (pictured below).<\/p>\r\n<img class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213354\/20140811155917317099.jpeg\" alt=\"Cabbage can be used as a home-made indicator\" width=\"400\" \/>\r\n\r\n<\/div>\r\n<h2>Indicators<\/h2>\r\n<p id=\"x-ck12-OGEwZDZlOTE1OTQyZDQ2OWM2MTc4ODAwZjIwZTA4MzY.-hsq\">An <strong> acid-base indicator <\/strong> is a substance that displays different colors when in the presence of an acid or a base. How does that work? An indicator is a weak acid that ionizes within a known pH range, usually about 2 pH units. We can represent the protonated form of the indicator molecule as HIn and the deprotonated form as In<sup>\u2212<\/sup>. The following equilibrium exists for the indicator.<\/p>\r\n<p id=\"x-ck12-qss\"><img id=\"x-ck12-MTM2ODczNzUxOTIwMQ..\" class=\"x-ck12-block-math\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213356\/0cfd7a657b4eebaa00175d61d6e97f2c.png\" alt=\"text{HIn}(aq) rightleftarrows text{H}^+(aq)+text{In}^-(aq)\" width=\"226\" height=\"21\" \/><\/p>\r\n<p id=\"x-ck12-ZmQ0Nzc0ZGY5ZWVmZmM5ZTE5OWZmNDI4ZmM2NThhMzQ.-8bo\">According to LeCh\u00e2telier\u2019s principle, the addition of H<sup>+ <\/sup> ions (as in a low pH solution) drives the equilibrium to the left and the protonated HIn predominates. The addition of OH<sup>\u2212 <\/sup> (as in a high pH solution) decreases the H<sup>+ <\/sup> concentration and drives the equilibrium to the right and the deprotonated In<sup>\u2212 <\/sup> predominates. To be useful as an indicator, the two forms must be different colors. In the case of phenolphthalein, the protonated form is colorless, while the deprotonated form is pink. <strong>Figure 1<\/strong>\u00a0shows a variety of acid-base indicators that can be used in titration experiments.<\/p>\r\n\r\n<div id=\"x-ck12-NmY0MjBhMWU4MjJlZjEwZmI0NDdiY2Q2MjM3NzQ0Yjc.-agy\" class=\"x-ck12-img-postcard x-ck12-nofloat\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"500\"]<img id=\"x-ck12-OTgwNDUtMTM2NDk5MTEyMy0xMy04Ni01LjUuNS4yNC4x\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213357\/20140811155917399854.png\" alt=\"Many indicators can be used for acid-base experiments\" width=\"500\" height=\"304\" longdesc=\"pH%20indicators.\" \/> Figure 1.\u00a0pH indicators.[\/caption]\r\n\r\n<\/div>\r\n<div id=\"x-ck12-NjFiMDgxZjkxMzRhOTViYTk4YjQ2OGNmNGQyMzRlMDk.-igp\" class=\"x-ck12-img-postcard x-ck12-nofloat\">\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"300\"]<img id=\"x-ck12-OTgwNDUtMTM2NDk5MTM0NC0zNC05OS01LjUuNS4yNC4y\" class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213358\/20140811155917529230.jpeg\" alt=\"Universal indicator can be used to quickly test the pH of a solution\" width=\"300\" height=\"259\" longdesc=\"Universal%20indicator%20tape.\" \/> Figure 2.\u00a0Universal indicator tape.[\/caption]\r\n\r\n<\/div>\r\n<p id=\"x-ck12-ZGM3ZjFhZDhiMzA1NDVlNTVmZGI2NDk4M2IxMzhkZGI.-rm2\">Depending on the pH at the equivalence point, the appropriate indicator must be chosen. For example, bromphenol blue has a yellow color below a pH of about 3 and a blue-violet color above a pH of about 4. Bromphenol blue would not be a good choice as the indicator for a strong acid-strong base titration, because the pH is 7 at the equivalence point. Instead, it could be used for a strong acid-weak base titration, where the pH at the equivalence point is lower.<\/p>\r\n<p id=\"x-ck12-NzllZGE5MGEwNzYwZjJiOWIzMDQyMmViNmExNmJjNmI.-9er\">Most indicators have two colored forms. Universal indicator displays the entire rainbow of colors from low pH to high pH (see <strong> Figure 2<\/strong>). Universal indicator is used to make pH paper, which can be used to quickly test solutions for their approximate pH.<\/p>\r\n\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Summary<\/h3>\r\n<ul id=\"x-ck12-OGVmYjUxN2QwODhjMTUyYzRjMzgyMjAyODZiOTIxYWM.-c2e\">\r\n \t<li>Acid-base indicator is defined.<\/li>\r\n \t<li>Examples of acid-base indicators are given.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<div class=\"textbox exercises\">\r\n<h3>Practice<\/h3>\r\n<p id=\"x-ck12-YmMzM2NmMmUyYzQ1NmUxNTQ2YTNmYjA2MWZlY2FkODA.-6dg\">Watch the video at the link below and answer the following questions:<\/p>\r\nhttps:\/\/youtu.be\/6Y4Y-__ME60\r\n<ol id=\"x-ck12-YmNlNjU3ODM0YzgwNTE3NWQwOWY2YTRjZDgyM2NiZmY.-kit\">\r\n \t<li>What was the acid used?<\/li>\r\n \t<li>What was the base used?<\/li>\r\n \t<li>What color was methyl orange in acid? in base?<\/li>\r\n \t<li>What color did indigo carmine turn in acid? in base?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div class=\"textbox exercises\">\r\n<h3>Review<\/h3>\r\n<ol id=\"x-ck12-Y2FhMTJjYTVkOTFhNGEzMGZlOWI3NTA2NWU4ZDg0MjU.-u3g\">\r\n \t<li>What is an indicator?<\/li>\r\n \t<li>What would be the best indicator to use around pH 1?<\/li>\r\n \t<li>What indicator besides phenolphthalein might you use for a pH 7 experiment?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<h2 class=\"x-ck12-data-problem-set\">Glossary<\/h2>\r\n<div class=\"x-ck12-data-vocabulary\">\r\n<ul id=\"x-ck12-ZWZlMmQ5NGU3OTYwZmQwNTE3OWU2NGM4Y2EwM2I3NzU.-26e\">\r\n \t<li><strong> acid-base indicator: <\/strong> A substance that displays different colors when in the presence of an acid or a base.<\/li>\r\n<\/ul>\r\n[reveal-answer q=\"836080\"]Show References[\/reveal-answer]\r\n[hidden-answer a=\"836080\"]\r\n<h2>References<\/h2>\r\n<ol>\r\n \t<li>Flickr: brittgow. <a href=\"http:\/\/www.flickr.com\/photos\/brittgow\/4782591644\/\">http:\/\/www.flickr.com\/photos\/brittgow\/4782591644\/ <\/a>.<\/li>\r\n \t<li>CK-12 Foundation - Joy Sheng, using data from http:\/\/en.wikipedia.org\/wiki\/PH_indicator.<\/li>\r\n \t<li>User:Bordercolliez\/Wikimedia Commons.<a href=\"http:\/\/commons.wikimedia.org\/wiki\/File:Universal_indicator_paper.jpg\">http:\/\/commons.wikimedia.org\/wiki\/File:Universal_indicator_paper.jpg <\/a>.<\/li>\r\n<\/ol>\r\n[\/hidden-answer]\r\n\r\n<\/div>","rendered":"<div class=\"x-ck12-data-objectives\">\n<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<ul>\n<li>Define indicator.<\/li>\n<li>Describe the use of indicators in acid-base experiments.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div class=\"textbox examples\">\n<h3><strong>Who would write a song about a cabbage? <\/strong><\/h3>\n<p id=\"x-ck12-ZWRhYTE5MTU2YmExZDhjYmE3OTM5NGVlZTU1MDdjOGM.-qtk\">There\u2019s an old bluegrass song known as \u201cBoil Them Cabbage Down\u201d (<a href=\"http:\/\/www.youtube.com\/watch?v=xT9TTlh5jgA\" target=\"_blank\">check out this great performance<\/a>). Many people enjoy the music, but chemistry students also enjoy the product of the boiled cabbage. Extracting the anthocyanin dye from cabbage leaves with boiling water gives a solution that is red when acidic, purple when neutral, and green to yellow when basic (pictured below).<\/p>\n<p><img decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213354\/20140811155917317099.jpeg\" alt=\"Cabbage can be used as a home-made indicator\" width=\"400\" \/><\/p>\n<\/div>\n<h2>Indicators<\/h2>\n<p id=\"x-ck12-OGEwZDZlOTE1OTQyZDQ2OWM2MTc4ODAwZjIwZTA4MzY.-hsq\">An <strong> acid-base indicator <\/strong> is a substance that displays different colors when in the presence of an acid or a base. How does that work? An indicator is a weak acid that ionizes within a known pH range, usually about 2 pH units. We can represent the protonated form of the indicator molecule as HIn and the deprotonated form as In<sup>\u2212<\/sup>. The following equilibrium exists for the indicator.<\/p>\n<p id=\"x-ck12-qss\"><img loading=\"lazy\" decoding=\"async\" id=\"x-ck12-MTM2ODczNzUxOTIwMQ..\" class=\"x-ck12-block-math\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213356\/0cfd7a657b4eebaa00175d61d6e97f2c.png\" alt=\"text{HIn}(aq) rightleftarrows text{H}^+(aq)+text{In}^-(aq)\" width=\"226\" height=\"21\" \/><\/p>\n<p id=\"x-ck12-ZmQ0Nzc0ZGY5ZWVmZmM5ZTE5OWZmNDI4ZmM2NThhMzQ.-8bo\">According to LeCh\u00e2telier\u2019s principle, the addition of H<sup>+ <\/sup> ions (as in a low pH solution) drives the equilibrium to the left and the protonated HIn predominates. The addition of OH<sup>\u2212 <\/sup> (as in a high pH solution) decreases the H<sup>+ <\/sup> concentration and drives the equilibrium to the right and the deprotonated In<sup>\u2212 <\/sup> predominates. To be useful as an indicator, the two forms must be different colors. In the case of phenolphthalein, the protonated form is colorless, while the deprotonated form is pink. <strong>Figure 1<\/strong>\u00a0shows a variety of acid-base indicators that can be used in titration experiments.<\/p>\n<div id=\"x-ck12-NmY0MjBhMWU4MjJlZjEwZmI0NDdiY2Q2MjM3NzQ0Yjc.-agy\" class=\"x-ck12-img-postcard x-ck12-nofloat\">\n<div style=\"width: 510px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" id=\"x-ck12-OTgwNDUtMTM2NDk5MTEyMy0xMy04Ni01LjUuNS4yNC4x\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213357\/20140811155917399854.png\" alt=\"Many indicators can be used for acid-base experiments\" width=\"500\" height=\"304\" longdesc=\"pH%20indicators.\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 1.\u00a0pH indicators.<\/p>\n<\/div>\n<\/div>\n<div id=\"x-ck12-NjFiMDgxZjkxMzRhOTViYTk4YjQ2OGNmNGQyMzRlMDk.-igp\" class=\"x-ck12-img-postcard x-ck12-nofloat\">\n<div style=\"width: 310px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" id=\"x-ck12-OTgwNDUtMTM2NDk5MTM0NC0zNC05OS01LjUuNS4yNC4y\" class=\"\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/53\/2014\/08\/19213358\/20140811155917529230.jpeg\" alt=\"Universal indicator can be used to quickly test the pH of a solution\" width=\"300\" height=\"259\" longdesc=\"Universal%20indicator%20tape.\" \/><\/p>\n<p class=\"wp-caption-text\">Figure 2.\u00a0Universal indicator tape.<\/p>\n<\/div>\n<\/div>\n<p id=\"x-ck12-ZGM3ZjFhZDhiMzA1NDVlNTVmZGI2NDk4M2IxMzhkZGI.-rm2\">Depending on the pH at the equivalence point, the appropriate indicator must be chosen. For example, bromphenol blue has a yellow color below a pH of about 3 and a blue-violet color above a pH of about 4. Bromphenol blue would not be a good choice as the indicator for a strong acid-strong base titration, because the pH is 7 at the equivalence point. Instead, it could be used for a strong acid-weak base titration, where the pH at the equivalence point is lower.<\/p>\n<p id=\"x-ck12-NzllZGE5MGEwNzYwZjJiOWIzMDQyMmViNmExNmJjNmI.-9er\">Most indicators have two colored forms. Universal indicator displays the entire rainbow of colors from low pH to high pH (see <strong> Figure 2<\/strong>). Universal indicator is used to make pH paper, which can be used to quickly test solutions for their approximate pH.<\/p>\n<div class=\"textbox key-takeaways\">\n<h3>Summary<\/h3>\n<ul id=\"x-ck12-OGVmYjUxN2QwODhjMTUyYzRjMzgyMjAyODZiOTIxYWM.-c2e\">\n<li>Acid-base indicator is defined.<\/li>\n<li>Examples of acid-base indicators are given.<\/li>\n<\/ul>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Practice<\/h3>\n<p id=\"x-ck12-YmMzM2NmMmUyYzQ1NmUxNTQ2YTNmYjA2MWZlY2FkODA.-6dg\">Watch the video at the link below and answer the following questions:<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Acid-Base Indicators\" width=\"500\" height=\"375\" src=\"https:\/\/www.youtube.com\/embed\/6Y4Y-__ME60?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<ol id=\"x-ck12-YmNlNjU3ODM0YzgwNTE3NWQwOWY2YTRjZDgyM2NiZmY.-kit\">\n<li>What was the acid used?<\/li>\n<li>What was the base used?<\/li>\n<li>What color was methyl orange in acid? in base?<\/li>\n<li>What color did indigo carmine turn in acid? in base?<\/li>\n<\/ol>\n<\/div>\n<div class=\"textbox exercises\">\n<h3>Review<\/h3>\n<ol id=\"x-ck12-Y2FhMTJjYTVkOTFhNGEzMGZlOWI3NTA2NWU4ZDg0MjU.-u3g\">\n<li>What is an indicator?<\/li>\n<li>What would be the best indicator to use around pH 1?<\/li>\n<li>What indicator besides phenolphthalein might you use for a pH 7 experiment?<\/li>\n<\/ol>\n<\/div>\n<h2 class=\"x-ck12-data-problem-set\">Glossary<\/h2>\n<div class=\"x-ck12-data-vocabulary\">\n<ul id=\"x-ck12-ZWZlMmQ5NGU3OTYwZmQwNTE3OWU2NGM4Y2EwM2I3NzU.-26e\">\n<li><strong> acid-base indicator: <\/strong> A substance that displays different colors when in the presence of an acid or a base.<\/li>\n<\/ul>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q836080\">Show References<\/span><\/p>\n<div id=\"q836080\" class=\"hidden-answer\" style=\"display: none\">\n<h2>References<\/h2>\n<ol>\n<li>Flickr: brittgow. <a href=\"http:\/\/www.flickr.com\/photos\/brittgow\/4782591644\/\">http:\/\/www.flickr.com\/photos\/brittgow\/4782591644\/ <\/a>.<\/li>\n<li>CK-12 Foundation &#8211; Joy Sheng, using data from http:\/\/en.wikipedia.org\/wiki\/PH_indicator.<\/li>\n<li>User:Bordercolliez\/Wikimedia Commons.<a href=\"http:\/\/commons.wikimedia.org\/wiki\/File:Universal_indicator_paper.jpg\">http:\/\/commons.wikimedia.org\/wiki\/File:Universal_indicator_paper.jpg <\/a>.<\/li>\n<\/ol>\n<\/div>\n<\/div>\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-2824\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Chemistry Concepts Intermediate. <strong>Authored by<\/strong>: Calbreath, Baxter, et al.. <strong>Provided by<\/strong>: CK12.org. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.ck12.org\/book\/CK-12-Chemistry-Concepts-Intermediate\/\">http:\/\/www.ck12.org\/book\/CK-12-Chemistry-Concepts-Intermediate\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC: Attribution-NonCommercial<\/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>","protected":false},"author":17,"menu_order":14,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Chemistry Concepts Intermediate\",\"author\":\"Calbreath, Baxter, et al.\",\"organization\":\"CK12.org\",\"url\":\"http:\/\/www.ck12.org\/book\/CK-12-Chemistry-Concepts-Intermediate\/\",\"project\":\"\",\"license\":\"cc-by-nc\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-2824","chapter","type-chapter","status-publish","hentry"],"part":2342,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapters\/2824","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":3,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapters\/2824\/revisions"}],"predecessor-version":[{"id":3048,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapters\/2824\/revisions\/3048"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/parts\/2342"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapters\/2824\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/wp\/v2\/media?parent=2824"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/pressbooks\/v2\/chapter-type?post=2824"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/wp\/v2\/contributor?post=2824"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/umes-cheminter\/wp-json\/wp\/v2\/license?post=2824"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}