{"id":189541,"date":"2025-02-09T19:25:54","date_gmt":"2025-02-09T19:25:54","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=189541"},"modified":"2025-02-09T19:25:56","modified_gmt":"2025-02-09T19:25:56","slug":"pure-benzene-freezes-at-5-50-degrees-celsius","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/02\/09\/pure-benzene-freezes-at-5-50-degrees-celsius\/","title":{"rendered":"Pure benzene freezes at 5.50 degrees celsius"},"content":{"rendered":"\n

Pure benzene freezes at 5.50 degrees celsius. When 10.06 g C10H8(naphthalene, MM = 128.16 g\/mol) is added to 100.0 g C6H6(benzene) the mixture freezes at 1.48 degrees celsius. What is the freezing point depression constant for benzene?<\/p>\n\n\n\n

The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n

Answer:<\/h3>\n\n\n\n

The freezing point depression constant (KfK_f) for benzene is 5.11 \u00b0C\u00b7kg\/mol<\/strong>.<\/p>\n\n\n\n

\n\n\n\n

Explanation:<\/h3>\n\n\n\n

Freezing point depression (\u0394Tf\\Delta T_f) occurs when a solute is added to a solvent, lowering the freezing temperature. The equation for freezing point depression is: \u0394Tf=Kf\u22c5m\\Delta T_f = K_f \\cdot m<\/p>\n\n\n\n

where:<\/p>\n\n\n\n

    \n
  • \u0394Tf\\Delta T_f is the change in freezing point,<\/li>\n\n\n\n
  • KfK_f is the freezing point depression constant (\u00b0C\u00b7kg\/mol),<\/li>\n\n\n\n
  • mm is the molality of the solute (mol\/kg solvent).<\/li>\n<\/ul>\n\n\n\n

    Step 1: Calculate Freezing Point Depression<\/strong><\/h4>\n\n\n\n

    The pure benzene freezes at 5.50\u00b0C<\/strong>, and the solution freezes at 1.48\u00b0C<\/strong>, so: \u0394Tf=5.50\u00b0C\u22121.48\u00b0C=4.02\u00b0C\\Delta T_f = 5.50\u00b0C – 1.48\u00b0C = 4.02\u00b0C<\/p>\n\n\n\n

    Step 2: Calculate the Molality of Naphthalene<\/strong><\/h4>\n\n\n\n

    Molality (mm) is defined as: m=moles of solutekg of solventm = \\frac{\\text{moles of solute}}{\\text{kg of solvent}}<\/p>\n\n\n\n

    First, calculate the moles of naphthalene (C10H8C_{10}H_8): Moles of C10H8=massmolar mass=10.06 g128.16 g\/mol=0.0785 mol\\text{Moles of } C_{10}H_8 = \\frac{\\text{mass}}{\\text{molar mass}} = \\frac{10.06 \\text{ g}}{128.16 \\text{ g\/mol}} = 0.0785 \\text{ mol}<\/p>\n\n\n\n

    Next, convert the solvent mass into kilograms: 100.0 g C6H6=0.1000 kg100.0 \\text{ g C}_6H_6 = 0.1000 \\text{ kg}<\/p>\n\n\n\n

    Now, calculate the molality: m=0.0785 mol0.1000 kg=0.785 mol\/kgm = \\frac{0.0785 \\text{ mol}}{0.1000 \\text{ kg}} = 0.785 \\text{ mol\/kg}<\/p>\n\n\n\n

    Step 3: Solve for KfK_f<\/strong><\/h4>\n\n\n\n

    Rearrange the equation to solve for KfK_f: Kf=\u0394Tfm=4.02\u00b0C0.785 mol\/kgK_f = \\frac{\\Delta T_f}{m} = \\frac{4.02\u00b0C}{0.785 \\text{ mol\/kg}} Kf=5.11\u00b0C\u22c5kg\/molK_f = 5.11\u00b0C \\cdot \\text{kg\/mol}<\/p>\n\n\n\n

    Thus, the freezing point depression constant for benzene is 5.11\u00b0C\u00b7kg\/mol<\/strong>.<\/p>\n\n\n\n

    This value is consistent with known literature values for benzene, confirming the accuracy of our calculations. The freezing point depression constant is crucial for determining molecular weights and colligative properties in chemistry.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Pure benzene freezes at 5.50 degrees celsius. When 10.06 g C10H8(naphthalene, MM = 128.16 g\/mol) is added to 100.0 g C6H6(benzene) the mixture freezes at 1.48 degrees celsius. What is the freezing point depression constant for benzene? The correct answer and explanation is: Answer: The freezing point depression constant (KfK_f) for benzene is 5.11 \u00b0C\u00b7kg\/mol. […]<\/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-189541","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/189541","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=189541"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/189541\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=189541"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=189541"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=189541"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}