{"id":85484,"date":"2025-06-01T03:18:36","date_gmt":"2025-06-01T03:18:36","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=85484"},"modified":"2025-06-01T03:18:36","modified_gmt":"2025-06-01T03:18:36","slug":"the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/","title":{"rendered":"The correct order of octane number of butane, pentane, hexane and cycl"},"content":{"rendered":"

The correct order of octane number of butane, pentane, hexane and cyclohexane is<\/p>\n

[amp_mcq option1=”butane > pentane > cyclohexane > hexane” option2=”butane > pentane > hexane > cyclohexane” option3=”butane > cyclohexane > pentane > hexane” option4=”cyclohexane > butane > pentane > hexane” correct=”option3″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC CDS-1 – 2024<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nOctane number is a measure of a fuel’s resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes.
\nComparing the standard (n-) forms:
\nn-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14).
\nn-Pentane has a higher octane number than n-hexane.
\nCyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane.
\nThe typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25).
\nThus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane.
\n<\/section>\n
\nOctane number is inversely related to chain length for n-alkanes and higher for branched\/cyclic structures compared to straight chains.
\n<\/section>\n
\nOctane numbers are determined relative to two reference hydrocarbons: isooctane (2,2,4-trimethylpentane), assigned an octane number of 100 (highly resistant to knocking), and n-heptane, assigned an octane number of 0 (knocks readily). The octane number of a fuel is the percentage of isooctane in a mixture with n-heptane that has the same knocking characteristics as the fuel.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

The correct order of octane number of butane, pentane, hexane and cyclohexane is [amp_mcq option1=”butane > pentane > cyclohexane > hexane” option2=”butane > pentane > hexane > cyclohexane” option3=”butane > cyclohexane > pentane > hexane” option4=”cyclohexane > butane > pentane > hexane” correct=”option3″] This question was previously asked in UPSC CDS-1 – 2024 Download PDFAttempt … <\/p>\n

Detailed SolutionThe correct order of octane number of butane, pentane, hexane and cycl<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1087],"tags":[1103,1096,1330],"class_list":["post-85484","post","type-post","status-publish","format-standard","hentry","category-upsc-cds-1","tag-1103","tag-chemistry","tag-hydrocarbons","no-featured-image-padding"],"yoast_head":"\nThe correct order of octane number of butane, pentane, hexane and cycl<\/title>\n<meta name=\"description\" content=\"Octane number is a measure of a fuel's resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes. Comparing the standard (n-) forms: n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14). n-Pentane has a higher octane number than n-hexane. Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane. The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25). Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane. Octane number is inversely related to chain length for n-alkanes and higher for branched\/cyclic structures compared to straight chains.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The correct order of octane number of butane, pentane, hexane and cycl\" \/>\n<meta property=\"og:description\" content=\"Octane number is a measure of a fuel's resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes. Comparing the standard (n-) forms: n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14). n-Pentane has a higher octane number than n-hexane. Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane. The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25). Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane. Octane number is inversely related to chain length for n-alkanes and higher for branched\/cyclic structures compared to straight chains.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T03:18:36+00:00\" \/>\n<meta name=\"author\" content=\"rawan239\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rawan239\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"The correct order of octane number of butane, pentane, hexane and cycl","description":"Octane number is a measure of a fuel's resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes. Comparing the standard (n-) forms: n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14). n-Pentane has a higher octane number than n-hexane. Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane. The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25). Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane. Octane number is inversely related to chain length for n-alkanes and higher for branched\/cyclic structures compared to straight chains.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/","og_locale":"en_US","og_type":"article","og_title":"The correct order of octane number of butane, pentane, hexane and cycl","og_description":"Octane number is a measure of a fuel's resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes. Comparing the standard (n-) forms: n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14). n-Pentane has a higher octane number than n-hexane. Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane. The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25). Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane. Octane number is inversely related to chain length for n-alkanes and higher for branched\/cyclic structures compared to straight chains.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T03:18:36+00:00","author":"rawan239","twitter_card":"summary_large_image","twitter_misc":{"Written by":"rawan239","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/","url":"https:\/\/exam.pscnotes.com\/mcq\/the-correct-order-of-octane-number-of-butane-pentane-hexane-and-cycl\/","name":"The correct order of octane number of butane, pentane, hexane and cycl","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T03:18:36+00:00","dateModified":"2025-06-01T03:18:36+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"Octane number is a measure of a fuel's resistance to knocking. Branched hydrocarbons and cyclic hydrocarbons have higher octane numbers than straight-chain hydrocarbons with the same number of carbon atoms. The octane number decreases with increasing chain length for straight-chain alkanes. Comparing the standard (n-) forms: n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14). n-Pentane has a higher octane number than n-hexane. Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane. The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25). Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane. 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