{"id":196599,"date":"2025-03-05T13:51:19","date_gmt":"2025-03-05T13:51:19","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=196599"},"modified":"2025-03-05T13:51:22","modified_gmt":"2025-03-05T13:51:22","slug":"phosphoric-acid-h3po4-is-a-weak-acid-naturally-found-in-the-body-that-supports-kidney-function-and-also-involved-in-fat-storage","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/03\/05\/phosphoric-acid-h3po4-is-a-weak-acid-naturally-found-in-the-body-that-supports-kidney-function-and-also-involved-in-fat-storage\/","title":{"rendered":"Phosphoric acid (H3PO4) is a weak acid naturally found in the body that supports kidney function and also involved in fat storage"},"content":{"rendered":"\n<p>Phosphoric acid (H3PO4) is a weak acid naturally found in the body that supports kidney function and also involved in fat storage. It is a weak acid with a Ka value of 6.9\u00c3\u0192\u00e2\u20ac\u201d10-3 at STP. (i) Determine the H+ concentration of a 0.25 M solution of phosphoric acid at STP (assume that the acid is monoacidic). (ii) Calculate the pH of the 0.25 M H3PO4 solution at STP. (iii) What effect on the pH of the solution would you expect to observe if the temperature of the weak solution was increased. Give a brief explanation for your answer.<br>Phosphoric acid (H3PO4) is a weak acid naturally found in the body that supports kidney function and also involved in fat storage. It is a weak acid with a Ka value of 6.9\u00c3\u0192\u00e2\u20ac\u201d10-3 at STP.<br>(i) Determine the H+ concentration of a 0.25 M solution of phosphoric acid at STP (assume that the acid is monoacidic).<\/p>\n\n\n\n<p>(ii) Calculate the pH of the 0.25 M H3PO4 solution at STP.<\/p>\n\n\n\n<p>(iii) What effect on the pH of the solution would you expect to observe if the temperature of the weak solution was increased. Give a brief explanation for your answer.<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-6-color\"><strong>The correct answer and explanation is :<\/strong><\/mark><\/p>\n\n\n\n<p>Phosphoric acid (H\u2083PO\u2084) is a triprotic acid, meaning it can donate up to three protons (H\u207a) in solution. However, for simplification, we&#8217;ll consider it as a monoprotic acid, focusing only on its first dissociation:\ue206<\/p>\n\n\n\n<p>[ \\text{H}_3\\text{PO}_4 \\rightleftharpoons \\text{H}^+ + \\text{H}_2\\text{PO}_4^- ]\ue206<\/p>\n\n\n\n<p>The acid dissociation constant (K\u2090) for this equilibrium is approximately 7.5 \u00d7 10\u207b\u00b3 at 25\u00b0C (standard temperature and pressure, STP). \ue200cite\ue202turn0search2\ue201\ue206<\/p>\n\n\n\n<p><strong>(i) Determining the H\u207a Concentration of a 0.25 M H\u2083PO\u2084 Solution at STP:<\/strong><\/p>\n\n\n\n<p>For a weak monoprotic acid, the dissociation constant K\u2090 is given by:\ue206<\/p>\n\n\n\n<p>[ K_a = \\frac{[\\text{H}^+][\\text{A}^-]}{[\\text{HA}]} ]\ue206<\/p>\n\n\n\n<p>Assuming the initial concentration of H\u2083PO\u2084 is 0.25 M and the degree of dissociation is small, we let the concentration of dissociated H\u207a be &#8216;x&#8217;. Thus:\ue206<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>[H\u207a] = x\ue206<\/li>\n\n\n\n<li>[H\u2082PO\u2084\u207b] = x\ue206<\/li>\n\n\n\n<li>[H\u2083PO\u2084] \u2248 0.25 &#8211; x \u2248 0.25 M (since x is small)\ue206<\/li>\n<\/ul>\n\n\n\n<p>Substituting into the K\u2090 expression:\ue206<\/p>\n\n\n\n<p>[ 7.5 \\times 10^{-3} = \\frac{x \\times x}{0.25} ]\ue206<\/p>\n\n\n\n<p>Simplifying:\ue206<\/p>\n\n\n\n<p>[ x^2 = 7.5 \\times 10^{-3} \\times 0.25 ]\ue206<\/p>\n\n\n\n<p>[ x^2 = 1.875 \\times 10^{-3} ]\ue206<\/p>\n\n\n\n<p>[ x = \\sqrt{1.875 \\times 10^{-3}} ]\ue206<\/p>\n\n\n\n<p>[ x \\approx 0.0433 \\, \\text{M} ]\ue206<\/p>\n\n\n\n<p>Therefore, the H\u207a concentration is approximately 0.0433 M.\ue206<\/p>\n\n\n\n<p><strong>(ii) Calculating the pH of the 0.25 M H\u2083PO\u2084 Solution at STP:<\/strong><\/p>\n\n\n\n<p>pH is defined as:\ue206<\/p>\n\n\n\n<p>[ \\text{pH} = -\\log[\\text{H}^+] ]\ue206<\/p>\n\n\n\n<p>Substituting the H\u207a concentration:\ue206<\/p>\n\n\n\n<p>[ \\text{pH} = -\\log(0.0433) ]\ue206<\/p>\n\n\n\n<p>[ \\text{pH} \\approx 1.36 ]\ue206<\/p>\n\n\n\n<p>Thus, the pH of the 0.25 M H\u2083PO\u2084 solution is approximately 1.36.\ue206<\/p>\n\n\n\n<p><strong>(iii) Effect of Temperature Increase on the pH of the Weak Acid Solution:<\/strong><\/p>\n\n\n\n<p>The dissociation of weak acids is temperature-dependent. Generally, increasing the temperature favors the endothermic dissociation process, leading to greater ionization of the acid. This results in a higher concentration of H\u207a ions, thereby lowering the pH of the solution. However, it&#8217;s important to note that the exact effect of temperature on pH can vary depending on the specific acid and its dissociation characteristics. \ue200cite\ue202turn0search9\ue201\ue206<\/p>\n\n\n\n<p>In summary, for a 0.25 M phosphoric acid solution at standard temperature and pressure, the H\u207a concentration is approximately 0.0433 M, corresponding to a pH of about 1.36. Increasing the temperature is expected to increase the ionization of the acid, leading to a decrease in pH.\ue206<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Phosphoric acid (H3PO4) is a weak acid naturally found in the body that supports kidney function and also involved in fat storage. It is a weak acid with a Ka value of 6.9\u00c3\u0192\u00e2\u20ac\u201d10-3 at STP. (i) Determine the H+ concentration of a 0.25 M solution of phosphoric acid at STP (assume that the acid is [&hellip;]<\/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-196599","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/196599","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=196599"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/196599\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=196599"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=196599"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=196599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}