{"id":88456,"date":"2025-06-01T07:11:34","date_gmt":"2025-06-01T07:11:34","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=88456"},"modified":"2025-06-01T07:11:34","modified_gmt":"2025-06-01T07:11:34","slug":"permanent-hardness-of-water-cannot-be-removed-by-which-one-of-the-fo","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/permanent-hardness-of-water-cannot-be-removed-by-which-one-of-the-fo\/","title":{"rendered":"Permanent hardness of water cannot be removed by which one of the fo"},"content":{"rendered":"

Permanent hardness of water cannot<\/b> be removed by which one of the following methods?<\/p>\n

[amp_mcq option1=”Treatment with washing soda” option2=”Calgon’s method” option3=”Boiling” option4=”Ion exchange method” correct=”option3″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC NDA-2 – 2018<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nPermanent hardness of water is caused by the presence of dissolved sulfates and chlorides of calcium and magnesium. Boiling only removes temporary hardness, which is caused by dissolved bicarbonates of calcium and magnesium (these decompose upon heating to form insoluble carbonates). Methods like treatment with washing soda (sodium carbonate), Calgon’s method (using sodium hexametaphosphate), and the ion exchange method (using resins or zeolites) are effective in removing permanent hardness by precipitating or exchanging the dissolved calcium and magnesium ions. Therefore, boiling cannot remove permanent hardness.
\n<\/section>\n
\nThis question distinguishes between temporary and permanent hardness of water and tests the knowledge of common methods used to remove water hardness.
\n<\/section>\n
\nTemporary hardness is removed by boiling because soluble bicarbonates (Ca(HCO\u2083)\u2082, Mg(HCO\u2083)\u2082) decompose into insoluble carbonates (CaCO\u2083, MgCO\u2083) which precipitate out. Permanent hardness requires chemical treatment or ion exchange to remove the Ca\u00b2\u207a and Mg\u00b2\u207a ions from the solution.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

Permanent hardness of water cannot be removed by which one of the following methods? [amp_mcq option1=”Treatment with washing soda” option2=”Calgon’s method” option3=”Boiling” option4=”Ion exchange method” correct=”option3″] This question was previously asked in UPSC NDA-2 – 2018 Download PDFAttempt Online Permanent hardness of water is caused by the presence of dissolved sulfates and chlorides of calcium … <\/p>\n

Detailed SolutionPermanent hardness of water cannot be removed by which one of the fo<\/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":[1094],"tags":[1114,1096,1161],"class_list":["post-88456","post","type-post","status-publish","format-standard","hentry","category-upsc-nda-2","tag-1114","tag-chemistry","tag-hydrogen-and-its-compounds","no-featured-image-padding"],"yoast_head":"\nPermanent hardness of water cannot be removed by which one of the fo<\/title>\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\/permanent-hardness-of-water-cannot-be-removed-by-which-one-of-the-fo\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Permanent hardness of water cannot be removed by which one of the fo\" \/>\n<meta property=\"og:description\" content=\"Permanent hardness of water cannot be removed by which one of the following methods? 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