{"id":198576,"date":"2025-03-10T07:09:55","date_gmt":"2025-03-10T07:09:55","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=198576"},"modified":"2025-03-10T07:09:58","modified_gmt":"2025-03-10T07:09:58","slug":"which-substance-has-the-lowest-vapor-pressure","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/03\/10\/which-substance-has-the-lowest-vapor-pressure\/","title":{"rendered":"Which substance has the lowest vapor pressure"},"content":{"rendered":"\n<p>Which substance has the lowest vapor pressure?<\/p>\n\n\n\n<p>A. H2O<\/p>\n\n\n\n<p>B. C3H8<\/p>\n\n\n\n<p>C. CH3OH<\/p>\n\n\n\n<p>D. H2S<\/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>The correct answer is <strong>A. H\u2082O (Water).<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p>Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature. A substance with <strong>stronger intermolecular forces<\/strong> has a <strong>lower vapor pressure<\/strong> because its molecules are held together more tightly, making it harder for them to escape into the gas phase.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>Comparison of Intermolecular Forces:<\/strong><\/h4>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Water (H\u2082O)<\/strong> \u2013 Water has <strong>strong hydrogen bonding<\/strong>, the strongest type of dipole-dipole interaction. Each water molecule can form <strong>up to four hydrogen bonds<\/strong>, significantly reducing its tendency to evaporate. This leads to a <strong>low vapor pressure<\/strong>.<\/li>\n\n\n\n<li><strong>Methanol (CH\u2083OH)<\/strong> \u2013 Also exhibits <strong>hydrogen bonding<\/strong>, but its hydrogen bonding is weaker than water\u2019s due to the presence of only one hydroxyl (-OH) group. This means methanol has a <strong>higher vapor pressure<\/strong> than water.<\/li>\n\n\n\n<li><strong>Hydrogen sulfide (H\u2082S)<\/strong> \u2013 Has dipole-dipole interactions but does <strong>not<\/strong> form hydrogen bonds because sulfur is less electronegative than oxygen. This results in <strong>higher vapor pressure<\/strong> than both water and methanol.<\/li>\n\n\n\n<li><strong>Propane (C\u2083H\u2088)<\/strong> \u2013 A nonpolar molecule that only experiences weak <strong>London dispersion forces<\/strong>. Since these forces are much weaker than hydrogen bonding or dipole interactions, propane molecules escape easily into the gas phase, resulting in <strong>very high vapor pressure<\/strong>.<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Conclusion:<\/strong><\/h3>\n\n\n\n<p>Water (<strong>H\u2082O<\/strong>) has the <strong>lowest vapor pressure<\/strong> among the given substances because of its <strong>strong hydrogen bonding<\/strong>, which keeps molecules in the liquid state more effectively than the others.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/03\/image-729.png\" alt=\"\" class=\"wp-image-198577\"\/><\/figure>\n\n\n\n<p>Here is the image comparing the vapor pressure of the four substances: Water (H\u2082O), Propane (C\u2083H\u2088), Methanol (CH\u2083OH), and Hydrogen Sulfide (H\u2082S). It visually represents how water has the lowest vapor pressure due to strong hydrogen bonding, while propane has the highest due to weak London dispersion forces. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>Which substance has the lowest vapor pressure? A. H2O B. C3H8 C. CH3OH D. H2S The correct answer and explanation is : The correct answer is A. H\u2082O (Water). Explanation: Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature. A substance with stronger intermolecular forces has [&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-198576","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/198576","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=198576"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/198576\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=198576"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=198576"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=198576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}