{"id":194922,"date":"2025-02-25T09:28:52","date_gmt":"2025-02-25T09:28:52","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=194922"},"modified":"2025-02-25T09:28:54","modified_gmt":"2025-02-25T09:28:55","slug":"octane-an-alkene-with-the-chemical-formula-c8h18-and-a-heat-of-combustion-of-46-8-mj-kg","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/02\/25\/octane-an-alkene-with-the-chemical-formula-c8h18-and-a-heat-of-combustion-of-46-8-mj-kg\/","title":{"rendered":"Octane, an alkene with the chemical formula C8H18 and a heat of combustion of 46.8 MJ\/kg"},"content":{"rendered":"\n

Octane, an alkene with the chemical formula C8H18 and a heat of combustion of 46.8 MJ\/kg,<\/p>\n\n\n\n

is the main constituent of gasoline. Assume gasoline contains 100% octane and has a density of 703 kg\/m3.<\/p>\n\n\n\n

The combustion reaction of octane is 2C8H18 + 25O2 ? 16CO2 + 18H2O. A typical car requires 3.4 MJ of<\/p>\n\n\n\n

energy to travel 1 km taking into account the various inefficiencies; and a typical driving distance is 15,200<\/p>\n\n\n\n

km per year. How many liters of octane does the car burn and what is the total mass of CO2 released from<\/p>\n\n\n\n

burning the octane in the engine? For that you will need to calculate some molecular weights, which you<\/p>\n\n\n\n

can do knowing: MW(H) = 1 g\/mol, MW(C) = 12 g\/mol, MW(O) = 16 g\/mol.<\/p>\n\n\n\n

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

The car burns approximately 1570.8 liters<\/strong> of octane per year and releases a total of 3409.7 kg (or 3.41 metric tons)<\/strong> of CO\u2082 into the atmosphere.<\/p>\n\n\n\n

\n\n\n\n

Explanation:<\/h3>\n\n\n\n
    \n
  1. Understanding Octane and Combustion<\/strong>:<\/li>\n<\/ol>\n\n\n\n
      \n
    • Octane (C\u2088H\u2081\u2088) is a hydrocarbon and the primary component of gasoline.<\/li>\n\n\n\n
    • The combustion reaction follows:
      [
      2C_8H_{18} + 25O_2 \u2192 16CO_2 + 18H_2O
      ]<\/li>\n\n\n\n
    • This means that 2 moles<\/strong> of octane produce 16 moles<\/strong> of CO\u2082.<\/li>\n<\/ul>\n\n\n\n
        \n
      1. Energy Requirements<\/strong>:<\/li>\n<\/ol>\n\n\n\n
          \n
        • The car requires 3.4 MJ\/km<\/strong> and travels 15,200 km\/year<\/strong>.<\/li>\n\n\n\n
        • The total energy needed per year is:
          [
          3.4 \\times 15,200 = 51,680 \\text{ MJ}
          ]<\/li>\n<\/ul>\n\n\n\n
            \n
          1. Finding the Mass of Octane<\/strong>:<\/li>\n<\/ol>\n\n\n\n
              \n
            • Given that octane releases 46.8 MJ\/kg<\/strong>, the required fuel mass is:
              [
              51,680 \\div 46.8 = 1104.3 \\text{ kg}
              ]<\/li>\n<\/ul>\n\n\n\n
                \n
              1. Finding the Volume of Octane<\/strong>:<\/li>\n<\/ol>\n\n\n\n
                  \n
                • Octane has a density of 703 kg\/m\u00b3<\/strong>, so the volume required is:
                  [
                  1104.3 \\div 703 = 1.57 \\text{ m\u00b3} = 1570.8 \\text{ liters}
                  ]<\/li>\n<\/ul>\n\n\n\n
                    \n
                  1. Calculating CO\u2082 Emissions<\/strong>:<\/li>\n<\/ol>\n\n\n\n
                      \n
                    • Molecular weight of octane<\/strong> = 114 g\/mol<\/strong><\/li>\n\n\n\n
                    • Molecular weight of CO\u2082<\/strong> = 44 g\/mol<\/strong><\/li>\n\n\n\n
                    • Using stoichiometry, 2 moles of octane (228 g) produce 16 moles of CO\u2082 (704 g)<\/strong>.<\/li>\n\n\n\n
                    • This means burning 1 kg of octane<\/strong> produces:
                      [
                      \\left(\\frac{16}{2} \\times \\frac{44}{114} \\right) \\times 1 = 3.09 \\text{ kg of CO\u2082}
                      ]<\/li>\n\n\n\n
                    • So, total CO\u2082 released:
                      [
                      1104.3 \\times 3.09 = 3409.7 \\text{ kg}
                      ]<\/li>\n<\/ul>\n\n\n\n

                      Thus, over a year, the car emits 3.41 metric tons of CO\u2082<\/strong>, significantly contributing to greenhouse gas emissions.<\/p>\n\n\n\n

                      Now, I’ll generate an image to visually represent this data.<\/p>\n\n\n\n

                      \"\"<\/figure>\n\n\n\n

                      Here is an illustration showing the car consuming 1570.8 liters of octane per year<\/strong> and emitting 3409.7 kg of CO\u2082 per year<\/strong>. The image visually represents fuel consumption and carbon dioxide emissions in a typical urban setting. Let me know if you need any modifications!<\/p>\n","protected":false},"excerpt":{"rendered":"

                      Octane, an alkene with the chemical formula C8H18 and a heat of combustion of 46.8 MJ\/kg, is the main constituent of gasoline. Assume gasoline contains 100% octane and has a density of 703 kg\/m3. The combustion reaction of octane is 2C8H18 + 25O2 ? 16CO2 + 18H2O. A typical car requires 3.4 MJ of energy […]<\/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-194922","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/194922","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=194922"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/194922\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=194922"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=194922"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=194922"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}