{"id":4275,"date":"2017-05-22T14:03:03","date_gmt":"2017-05-22T12:03:03","guid":{"rendered":"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/?p=4275"},"modified":"2017-05-22T14:03:03","modified_gmt":"2017-05-22T12:03:03","slug":"duresa-de-laigua","status":"publish","type":"post","link":"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/modul-a\/duresa-de-laigua\/","title":{"rendered":"Duresa de l&#8217;aigua"},"content":{"rendered":"<p><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-large wp-image-4276\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2-1024x768.jpg\" alt=\"34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2\" width=\"1024\" height=\"768\" srcset=\"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2-1024x768.jpg 1024w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2-300x225.jpg 300w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2-768x576.jpg 768w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/34562D65-7A2A-47C8-BCBA-7F8F37BE8DC2-200x150.jpg 200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">La duresa de l&#8217;aigua \u00e9s deguda a certs cations\u00a0dissolts en aigua que interfereixen en la producci\u00f3 d&#8217;escuma dels sabons de sodi (Na) i potassi (K), ja que es forma un precipitat insoluble.<\/p>\n<p style=\"text-align: justify;\">Aix\u00ed doncs, direm que la duresa de l&#8217;aigua la constitueixen tots els cations polivalents (amb m\u00e9s d&#8217;una c\u00e0rrega positiva) dissolts. Tot i aix\u00f2, la concentraci\u00f3 de calci (Ca<sup>2+<\/sup>) i magnesi (Mg<sup>2+<\/sup>) excedeix de molt les concentracions dels altres cations polivalents. \u00c9s per aix\u00f2, que la duresa se sol associar habitualment al contingut en sals de Ca i Mg.<\/p>\n<p><!--more--><\/p>\n<p style=\"text-align: justify;\">Les principals conseq\u00fc\u00e8ncies de la duresa de l&#8217;aigua s\u00f3n:<\/p>\n<ul style=\"text-align: justify;\">\n<li>Per obtenir el mateix efecte del detergent, s&#8217;ha d&#8217;utilitzar m\u00e9s sab\u00f3.<\/li>\n<li>Dificulta la cocci\u00f3 dels llegums, ja que el Ca i el Mg de l&#8217;aigua reaccionen amb la capa m\u00e9s externa.<\/li>\n<li>Aparici\u00f3 d&#8217;incrustacions als recipients, a causa del carbonat de calci (CaCO<sub>3<\/sub>).<\/li>\n<li>Disminueixen les incid\u00e8ncies cardiovasculars, una de les poques conseq\u00fc\u00e8ncies positives de la duresa de l&#8217;aigua.<\/li>\n<li>La pell i el cabell augmenten la seva rigidesa a causa dels cations polivalents dissolts.<\/li>\n<li>Augmenten la formaci\u00f3 de c\u00e0lculs renals i vesiculars (pedres d&#8217;oxalat).<\/li>\n<\/ul>\n<p style=\"text-align: justify;\">Al laboratori de Qu\u00edmica Anal\u00edtica, hem realitzat, mitjan\u00e7ant una valoraci\u00f3 complexometria la duresa total, la c\u00e0lcica i la magn\u00e8sica. Realment, fent la resta entre a duresa total i la c\u00e0lcica, obtenim el resultat de la m\u00e0gnesica, es per aix\u00f2, que vam realitzar dos valoracions.<\/p>\n<p style=\"text-align: justify;\"><strong>DURESA TOTAL<\/strong><\/p>\n<p style=\"text-align: justify;\">Utilitzem com indicador el NET (o camalgita), hem d&#8217;augmentar el pH fins a 10 (afegint una soluci\u00f3 tamp\u00f3 d&#8217;amon\u00edac\/amoni), perqu\u00e8 el valorant, en aquest cas EDTA 0,025M \u00e9s m\u00e9s efica\u00e7 a pH b\u00e0sics, ja que allibera tots els protons i presenta 6 punts de coordinaci\u00f3 per unir-se amb el metall. El viratge del NET va de violat (NET con Mg) a blau (NET lliure). \u00a0Amb els mL consumits de EDTA 0,025M i l&#8217;estequiometria de les reaccions poden con\u00e8ixer la duresa total en mg CaCO<sub>3<\/sub>\/L.<\/p>\n<p style=\"text-align: justify;\"><strong><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-large wp-image-4279\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE-1024x768.jpg\" alt=\"4B918032-DED3-4345-A957-8666593A6EFE\" width=\"1024\" height=\"768\" srcset=\"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE-1024x768.jpg 1024w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE-300x225.jpg 300w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE-768x576.jpg 768w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/4B918032-DED3-4345-A957-8666593A6EFE-200x150.jpg 200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><\/strong><\/p>\n<p style=\"text-align: justify;\">Viratge del NET amb unes gotes de Roig de Metil (altera els colors del viratge del NET)<\/p>\n<p style=\"text-align: justify;\"><strong><a href=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-4278 alignleft\" src=\"http:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A-1024x768.jpg\" alt=\"Viratge NET amb unes gotes de Roig de Metil\" width=\"1024\" height=\"768\" srcset=\"https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A-1024x768.jpg 1024w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A-300x225.jpg 300w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A-768x576.jpg 768w, https:\/\/agora.xtec.cat\/ies-merce-rodoreda\/wp-content\/uploads\/usu644\/2017\/04\/EEF3035E-3674-4271-A9A6-0156E75DFF6A-200x150.jpg 200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><\/strong><\/p>\n<p style=\"text-align: justify;\"><strong>DURESA C\u00c0LCICA<\/strong><\/p>\n<p style=\"text-align: justify;\">Utilitzem com indicador la Murexida (o calc\u00f3n carboxilic), el pH ha de ser augmentat fins a 12 (afegint NaOH) per emmascarar el Mg que precipita en forma d&#8217;hidr\u00f2xid (Mg(OH)<sub>2<\/sub>). Un cop emmascarat, amb el mateix valorant, EDTA 0,025M, valorem l&#8217;aigua problema. El viratge de la murexida va de rosa intens a lila intens (veure imatge 1).\u00a0Amb els mL consumits de EDTA 0,025M i l&#8217;estequiometria de les reaccions poden con\u00e8ixer la duresa c\u00e0lcica en mg CaCO<sub>3<\/sub>\/L (veure imatge inicial)<\/p>\n<p style=\"text-align: justify;\"><strong>DURESA MAGN\u00c8SICA<\/strong><\/p>\n<p style=\"text-align: justify;\">Mitjan\u00e7ant la resta entre la duresa total i la c\u00e0lcica obtenim la duresa magn\u00e8sica\u00a0en mg CaCO<sub>3<\/sub>\/L.<\/p>\n<p style=\"text-align: justify;\">\n<p style=\"text-align: justify;\">\u00a0Marc<\/p>\n","protected":false},"excerpt":{"rendered":"<p>La duresa de l&#8217;aigua \u00e9s deguda a certs cations\u00a0dissolts en aigua que interfereixen en la producci\u00f3 d&#8217;escuma dels sabons de [&hellip;]<\/p>\n","protected":false},"author":144,"featured_media":4276,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","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":"","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":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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