{"id":259734,"date":"2025-07-19T05:17:43","date_gmt":"2025-07-19T05:17:43","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=259734"},"modified":"2025-07-19T05:17:46","modified_gmt":"2025-07-19T05:17:46","slug":"0-006-50-m-solution-of-ethanolamine-h_2nch_2ch_2oh-has-a-ph-of-10-64-at-25-deg-c-calculate-the-k_b-of-ethanolamine","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/19\/0-006-50-m-solution-of-ethanolamine-h_2nch_2ch_2oh-has-a-ph-of-10-64-at-25-deg-c-calculate-the-k_b-of-ethanolamine\/","title":{"rendered":"0.006 50 M solution of ethanolamine, H_{2}NCH_{2}CH_{2}*OH has a pH of 10.64 at 25 deg * C Calculate the K_{b} of ethanolamine."},"content":{"rendered":"\n

0.006 50 M solution of ethanolamine, H_{2}NC<\/em>H_{2}C<\/em>H_{2}*OH has a pH of 10.64 at 25 deg * C Calculate the K_{b} of ethanolamine. What concentra- tion of undissociated ethanolamine remains at equilibrium?<\/p>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n

To solve for the Kb<\/strong> of ethanolamine and the concentration of undissociated ethanolamine at equilibrium, we need to break down the process step by step.<\/p>\n\n\n\n

Step 1: Write the reaction for the dissociation of ethanolamine<\/h3>\n\n\n\n

Ethanolamine, a weak base, dissociates in water as follows:H2NC2H4OH+H2O\u21ccH2NC2H4OH2++OH\u2212\\text{H}_2\\text{NC}_2\\text{H}_4\\text{OH} + \\text{H}_2\\text{O} \\rightleftharpoons \\text{H}_2\\text{NC}_2\\text{H}_4\\text{OH}_2^+ + \\text{OH}^-H2\u200bNC2\u200bH4\u200bOH+H2\u200bO\u21ccH2\u200bNC2\u200bH4\u200bOH2+\u200b+OH\u2212<\/p>\n\n\n\n

Here, ethanolamine reacts with water to produce ethanolamine protonated (ethanolammonium ion) and hydroxide ions. The equilibrium constant for this reaction is Kb<\/strong>.<\/p>\n\n\n\n

Step 2: Use the given pH to find [OH\u207b]<\/h3>\n\n\n\n

The pH is given as 10.64, so we can calculate the pOH using the relation:pOH=14\u2212pH\\text{pOH} = 14 – \\text{pH}pOH=14\u2212pHpOH=14\u221210.64=3.36\\text{pOH} = 14 – 10.64 = 3.36pOH=14\u221210.64=3.36<\/p>\n\n\n\n

Now, calculate the concentration of hydroxide ions ([OH\u207b]):[OH\u2212]=10\u2212pOH=10\u22123.36\u22484.37\u00d710\u22124\u2009M[\\text{OH}^-] = 10^{-\\text{pOH}} = 10^{-3.36} \\approx 4.37 \\times 10^{-4} \\, \\text{M}[OH\u2212]=10\u2212pOH=10\u22123.36\u22484.37\u00d710\u22124M<\/p>\n\n\n\n

Step 3: Set up an ICE table<\/h3>\n\n\n\n

We now set up the ICE<\/strong> (Initial, Change, Equilibrium) table for the dissociation of ethanolamine. Let x<\/strong> be the concentration of ethanolamine that dissociates:<\/p>\n\n\n\n

Component<\/th>Initial (M)<\/th>Change (M)<\/th>Equilibrium (M)<\/th><\/tr><\/thead>
Ethanolamine (H\u2082NC\u2082H\u2084OH)<\/td>0.00650<\/td>-x<\/td>0.00650 – x<\/td><\/tr>
Ethanolamine ion (H\u2082NC\u2082H\u2084OH\u2082\u207a)<\/td>0<\/td>+x<\/td>x<\/td><\/tr>
Hydroxide ion (OH\u207b)<\/td>0<\/td>+x<\/td>x<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

From the ICE table, we know that at equilibrium, [OH\u207b] = x<\/strong>. Thus, x = 4.37 \u00d7 10\u207b\u2074 M<\/strong>.<\/p>\n\n\n\n

Step 4: Solve for Kb<\/h3>\n\n\n\n

The expression for the base dissociation constant Kb<\/strong> is:Kb=[H2NC2H4OH2+][OH\u2212][H2NC2H4OH]K_b = \\frac{[\\text{H}_2\\text{NC}_2\\text{H}_4\\text{OH}_2^+][\\text{OH}^-]}{[\\text{H}_2\\text{NC}_2\\text{H}_4\\text{OH}]}Kb\u200b=[H2\u200bNC2\u200bH4\u200bOH][H2\u200bNC2\u200bH4\u200bOH2+\u200b][OH\u2212]\u200b<\/p>\n\n\n\n

Substitute the known values into this equation:Kb=x\u00d7x0.00650\u2212xK_b = \\frac{x \\times x}{0.00650 – x}Kb\u200b=0.00650\u2212xx\u00d7x\u200bKb=(4.37\u00d710\u22124)20.00650\u22124.37\u00d710\u22124\u22481.91\u00d710\u221270.00611\u22483.13\u00d710\u22125K_b = \\frac{(4.37 \\times 10^{-4})^2}{0.00650 – 4.37 \\times 10^{-4}} \\approx \\frac{1.91 \\times 10^{-7}}{0.00611} \\approx 3.13 \\times 10^{-5}Kb\u200b=0.00650\u22124.37\u00d710\u22124(4.37\u00d710\u22124)2\u200b\u22480.006111.91\u00d710\u22127\u200b\u22483.13\u00d710\u22125<\/p>\n\n\n\n

Thus, the Kb<\/strong> of ethanolamine is approximately 3.13 \u00d7 10\u207b\u2075<\/strong>.<\/p>\n\n\n\n

Step 5: Find the concentration of undissociated ethanolamine at equilibrium<\/h3>\n\n\n\n

The concentration of undissociated ethanolamine at equilibrium is:[H2NC2H4OH]=0.00650\u2212x=0.00650\u22124.37\u00d710\u22124\u22480.00606\u2009M[\\text{H}_2\\text{NC}_2\\text{H}_4\\text{OH}] = 0.00650 – x = 0.00650 – 4.37 \\times 10^{-4} \\approx 0.00606 \\, \\text{M}[H2\u200bNC2\u200bH4\u200bOH]=0.00650\u2212x=0.00650\u22124.37\u00d710\u22124\u22480.00606M<\/p>\n\n\n\n

Final Answer:<\/h3>\n\n\n\n
    \n
  • The Kb<\/strong> of ethanolamine is 3.13 \u00d7 10\u207b\u2075<\/strong>.<\/li>\n\n\n\n
  • The concentration of undissociated ethanolamine at equilibrium is approximately 0.00606 M<\/strong>.<\/li>\n<\/ul>\n\n\n\n
    \"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

    0.006 50 M solution of ethanolamine, H_{2}NCH_{2}CH_{2}*OH has a pH of 10.64 at 25 deg * C Calculate the K_{b} of ethanolamine. What concentra- tion of undissociated ethanolamine remains at equilibrium? The Correct Answer and Explanation is: To solve for the Kb of ethanolamine and the concentration of undissociated ethanolamine at equilibrium, we need to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-259734","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/259734","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=259734"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/259734\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=259734"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=259734"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=259734"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}