{"id":214911,"date":"2025-05-16T03:18:42","date_gmt":"2025-05-16T03:18:42","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=214911"},"modified":"2025-05-16T03:18:50","modified_gmt":"2025-05-16T03:18:50","slug":"what-is-the-difference-between-r-and-ru","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/16\/what-is-the-difference-between-r-and-ru\/","title":{"rendered":"What is the difference between R and Ru"},"content":{"rendered":"\n

What is the difference between R and Ru? How are these two related?<\/p>\n\n\n\n

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

Correct Answer:<\/strong><\/p>\n\n\n\n

R<\/strong> typically refers to the universal gas constant<\/strong>, while Ru<\/strong> refers to the universal gas constant per mole<\/strong> (often also denoted as R\u0305<\/strong>). In practice, R and Ru are often the same and used interchangeably<\/strong>, but they are conceptually linked to different contexts depending on the formulation of the ideal gas law\u2014whether it\u2019s based on moles<\/strong> or mass<\/strong>.<\/p>\n\n\n\n

\n\n\n\n

Detailed Explanation (300+ words):<\/strong><\/h3>\n\n\n\n

In thermodynamics and physical chemistry, the ideal gas law<\/strong> is a fundamental equation that relates pressure, volume, temperature, and amount of gas. The equation can be expressed in two different forms, depending on whether you use moles (n)<\/strong> or mass (m)<\/strong>:<\/p>\n\n\n\n

    \n
  1. Molar form of the ideal gas law:<\/strong> PV=nRuTPV = nRuT\n
      \n
    • Here, P<\/strong> is pressure, V<\/strong> is volume, n<\/strong> is the number of moles, T<\/strong> is temperature in Kelvin, and Ru<\/strong> is the universal gas constant<\/strong> (also written as R\u0305<\/strong>).<\/li>\n\n\n\n
    • Its value is: Ru=8.314\u00a0J\/mol\\cdotpKRu = 8.314\\ \\text{J\/mol\u00b7K}<\/li>\n<\/ul>\n<\/li>\n\n\n\n
    • Mass-based form of the ideal gas law:<\/strong> PV=mRTPV = mRT\n
        \n
      • Here, m<\/strong> is the mass of the gas, and R<\/strong> is the specific gas constant<\/strong>.<\/li>\n\n\n\n
      • The specific gas constant R<\/strong> is related to Ru<\/strong> by: R=RuMR = \\frac{Ru}{M} where M<\/strong> is the molar mass of the specific gas (in kg\/mol).<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n
        \n\n\n\n

        Relationship Between R and Ru:<\/strong><\/h3>\n\n\n\n
          \n
        • Ru<\/strong> is constant for all ideal gases.<\/li>\n\n\n\n
        • R<\/strong> varies depending on the type of gas<\/strong>, since it depends on the gas\u2019s molar mass.<\/li>\n\n\n\n
        • For example, the specific gas constant for dry air is: R=8.314\u00a0J\/mol\\cdotpK0.02897\u00a0kg\/mol\u2248287\u00a0J\/kg\\cdotpKR = \\frac{8.314\\ \\text{J\/mol\u00b7K}}{0.02897\\ \\text{kg\/mol}} \\approx 287\\ \\text{J\/kg\u00b7K}<\/li>\n<\/ul>\n\n\n\n
          \n\n\n\n

          Summary:<\/strong><\/h3>\n\n\n\n
            \n
          • Ru (or R\u0305)<\/strong> is the universal<\/strong> gas constant per mole.<\/li>\n\n\n\n
          • R<\/strong> is the specific<\/strong> gas constant per kilogram, unique to each gas.<\/li>\n\n\n\n
          • They are related by:\u2003R = Ru \/ <\/strong><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

            What is the difference between R and Ru? How are these two related? The Correct Answer and Explanation is: Correct Answer: R typically refers to the universal gas constant, while Ru refers to the universal gas constant per mole (often also denoted as R\u0305). In practice, R and Ru are often the same and used […]<\/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-214911","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/214911","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=214911"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/214911\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=214911"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=214911"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=214911"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}