{"id":87018,"date":"2025-06-01T04:26:20","date_gmt":"2025-06-01T04:26:20","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=87018"},"modified":"2025-06-01T04:26:20","modified_gmt":"2025-06-01T04:26:20","slug":"which-one-of-the-following-statements-about-fehlings-test-is-not","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/","title":{"rendered":"Which one of the following statements about Fehling’s test is not"},"content":{"rendered":"

Which one of the following statements about Fehling’s test is not correct?<\/p>\n

[amp_mcq option1=”Fehling’s A solution is aqueous copper sulphate.” option2=”Fructose gives a positive Fehling’s test.” option3=”Red-brown ppt of CuO is obtained in the reaction.” option4=”Aromatic aldehydes do not respond to this test.” correct=”option3″]<\/p>\n

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This question was previously asked in<\/div>\n
UPSC Geoscientist – 2023<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nFehling’s test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling’s solution, which is prepared fresh by mixing Fehling’s A (aqueous copper(II) sulfate) and Fehling’s B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose – due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling’s solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect.
\n<\/section>\n
\nFehling’s test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.
\n<\/section>\n
\nFehling’s test is positive for all reducing sugars and most aliphatic aldehydes. Ketones generally do not give a positive Fehling’s test, except for alpha-hydroxy ketones like fructose, which isomerize under alkaline conditions to aldoses. Aromatic aldehydes, with a few exceptions, do not give a positive Fehling’s test because they are not easily oxidized and may undergo competing reactions like the Cannizzaro reaction in the presence of strong alkali. Statement A and B are correct. Statement D is generally correct for typical aromatic aldehydes.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

Which one of the following statements about Fehling’s test is not correct? [amp_mcq option1=”Fehling’s A solution is aqueous copper sulphate.” option2=”Fructose gives a positive Fehling’s test.” option3=”Red-brown ppt of CuO is obtained in the reaction.” option4=”Aromatic aldehydes do not respond to this test.” correct=”option3″] This question was previously asked in UPSC Geoscientist – 2023 Download … <\/p>\n

Detailed SolutionWhich one of the following statements about Fehling’s test is not<\/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":[1091],"tags":[1105,1096,1272],"class_list":["post-87018","post","type-post","status-publish","format-standard","hentry","category-upsc-geoscientist","tag-1105","tag-chemistry","tag-organic-chemistry","no-featured-image-padding"],"yoast_head":"\nWhich one of the following statements about Fehling's test is not<\/title>\n<meta name=\"description\" content=\"Fehling's test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling's solution, which is prepared fresh by mixing Fehling's A (aqueous copper(II) sulfate) and Fehling's B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose - due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling's solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect. Fehling's test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.\" \/>\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\/which-one-of-the-following-statements-about-fehlings-test-is-not\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Which one of the following statements about Fehling's test is not\" \/>\n<meta property=\"og:description\" content=\"Fehling's test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling's solution, which is prepared fresh by mixing Fehling's A (aqueous copper(II) sulfate) and Fehling's B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose - due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling's solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect. Fehling's test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T04:26:20+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":"Which one of the following statements about Fehling's test is not","description":"Fehling's test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling's solution, which is prepared fresh by mixing Fehling's A (aqueous copper(II) sulfate) and Fehling's B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose - due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling's solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect. Fehling's test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.","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\/which-one-of-the-following-statements-about-fehlings-test-is-not\/","og_locale":"en_US","og_type":"article","og_title":"Which one of the following statements about Fehling's test is not","og_description":"Fehling's test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling's solution, which is prepared fresh by mixing Fehling's A (aqueous copper(II) sulfate) and Fehling's B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose - due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling's solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect. Fehling's test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T04:26:20+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\/which-one-of-the-following-statements-about-fehlings-test-is-not\/","url":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/","name":"Which one of the following statements about Fehling's test is not","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T04:26:20+00:00","dateModified":"2025-06-01T04:26:20+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"Fehling's test is a qualitative test used to distinguish between reducing and non-reducing sugars, and also to detect aldehydes. It involves Fehling's solution, which is prepared fresh by mixing Fehling's A (aqueous copper(II) sulfate) and Fehling's B (aqueous sodium potassium tartrate and a strong alkali like NaOH or KOH). Reducing sugars (like glucose, fructose - due to isomerization) and aldehydes reduce the blue copper(II) ions (Cu\u00b2\u207a) in Fehling's solution to red-brown copper(I) oxide (Cu\u2082O) precipitate. Statement C claims the precipitate is red-brown CuO (copper(II) oxide), which is black. The precipitate formed is red-brown Cu\u2082O (copper(I) oxide). Therefore, statement C is incorrect. Fehling's test involves the reduction of Cu\u00b2\u207a ions to Cu\u207a ions, forming a red-brown precipitate of Cu\u2082O.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/which-one-of-the-following-statements-about-fehlings-test-is-not\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC Geoscientist","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-geoscientist\/"},{"@type":"ListItem","position":3,"name":"Which one of the following statements about Fehling’s test is not"}]},{"@type":"WebSite","@id":"https:\/\/exam.pscnotes.com\/mcq\/#website","url":"https:\/\/exam.pscnotes.com\/mcq\/","name":"MCQ and Quiz for Exams","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/exam.pscnotes.com\/mcq\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209","name":"rawan239","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","caption":"rawan239"},"sameAs":["https:\/\/exam.pscnotes.com"],"url":"https:\/\/exam.pscnotes.com\/mcq\/author\/rawan239\/"}]}},"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/87018","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/comments?post=87018"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/87018\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=87018"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=87018"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=87018"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}