{"id":6827,"date":"2015-06-16T12:42:53","date_gmt":"2015-06-16T10:42:53","guid":{"rendered":"https:\/\/kamerpower.com\/?p=6827"},"modified":"2015-06-16T13:06:00","modified_gmt":"2015-06-16T11:06:00","slug":"epreuve-concours-ensp-physique-et-chimie-1-cameroun","status":"publish","type":"post","link":"https:\/\/kamerpower.com\/fr\/epreuve-concours-ensp-physique-et-chimie-1-cameroun\/","title":{"rendered":"Epreuve Concours ENSP Physique et Chimie Cameroun 1 concours d&#8217;entr\u00e9e \u00e0 l\u2019Ecole Nationale Sup\u00e9rieure Polytechnique"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Contents<\/p>\n<label for=\"ez-toc-cssicon-toggle-item-69e24e4d8a4f5\" class=\"ez-toc-cssicon-toggle-label\"><span class=\"ez-toc-cssicon\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #000000;color:#000000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #000000;color:#000000\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-69e24e4d8a4f5\"  aria-label=\"Toggle\" \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/kamerpower.com\/fr\/epreuve-concours-ensp-physique-et-chimie-1-cameroun\/#epreuve-concours-ensp-physique-et-chimie-1\" >Epreuve Concours ENSP Physique et Chimie 1<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/kamerpower.com\/fr\/epreuve-concours-ensp-physique-et-chimie-1-cameroun\/#kamerpower-probleme-1\" >Kamerpower Probl\u00e8me\u00a01<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/kamerpower.com\/fr\/epreuve-concours-ensp-physique-et-chimie-1-cameroun\/#kamerpower-probleme-2\" >Kamerpower Probl\u00e8me\u00a02<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/kamerpower.com\/fr\/epreuve-concours-ensp-physique-et-chimie-1-cameroun\/#epreuve-concours-ensp-physique-et-chimie-cameroun-1-concours-dentree-a-lecole-nationale-superieure-polytechnique\" >Epreuve Concours ENSP Physique et Chimie Cameroun 1 concours d&#8217;entr\u00e9e \u00e0 l\u2019Ecole Nationale Sup\u00e9rieure Polytechnique<\/a><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: center;\"><span class=\"ez-toc-section\" id=\"epreuve-concours-ensp-physique-et-chimie-1\"><\/span><span style=\"color: #000000;\"><strong>Epreuve Concours ENSP Physique et Chimie 1<\/strong><\/span><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: center;\"><span style=\"color: #000000;\">Ecole Nationale Superieure Polytechnique<br \/>\n(\u00c9preuve\u00a0de Physique et Chimie ENSP)<\/span><br \/>\n<span style=\"color: #008000; text-shadow: 2px 0 2px #000;\">KA<\/span><span style=\"color: #ff0000; text-shadow: 2px 0 2px #000;\">M<\/span><span style=\"color: #ffcc00; text-shadow: 2px 0 2px #000;\">ER<\/span><span style=\"color: #800080; text-shadow: 2px 0 2px #000;\">POWER<\/span><span style=\"color: #3366ff; text-shadow: 2px 0 2px #000;\">.COM<\/span><\/p>\n<h3 style=\"text-align: center;\"><span class=\"ez-toc-section\" id=\"kamerpower-probleme-1\"><\/span><span style=\"color: #3366ff;\">Kamerpower Probl\u00e8me\u00a01<\/span><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\"><span style=\"color: #000000;\">Le paquebot <span style=\"color: #ff0000;\">Narcisse<\/span> aborde la c\u00f4te anglaise par temps calme, dans un \u00e9pais de brouillard, et se dirige droit vers la falaise \u00e0 une vitesse <span style=\"color: #ff0000;\">V<\/span> constante. Il envoie toutes les minutes un coup de sir\u00e8ne bref.\u00a0<\/span><\/p>\n<ol>\n<li style=\"text-align: justify;\"><span style=\"color: #000000;\"><span style=\"color: #000000;\">Sachant que la vitesse du son dans l\u2019air est <span style=\"color: #ff0000;\">n=330 m.s<sup>-1<\/sup><\/span>, et que le premier \u00e9cho est entendu au bout d\u2019un temps <span style=\"color: #ff0000;\">T<sub>1<\/sub>=18 s<\/span> apr\u00e8s le premier coup de sir\u00e8ne\u00a0; le deuxi\u00e8me \u00e9cho au bout d\u2019un temps <span style=\"color: #ff0000;\">T<sub>2<\/sub>=15 s<\/span> apr\u00e8s le deuxi\u00e8me coup de sir\u00e8ne, Calculer la vitesse <span style=\"color: #ff0000;\">V<\/span> du paquebot, ainsi que la distance <span style=\"color: #ff0000;\">D<\/span> qui s\u00e9pare la falaise du paquebot au moment o\u00f9 celui-ci envoie le premier coup de sir\u00e8ne.\u00a0<\/span><\/span><span style=\"color: #000000;\">(on appellera <span style=\"color: #ff0000;\">A<sub>1<\/sub><\/span> le point o\u00f9 est \u00e9mis le premier coup de sir\u00e8ne, et <span style=\"color: #ff0000;\">A<sub>2<\/sub><\/span> le point o\u00f9 est \u00e9mis le deuxi\u00e8me coup de sir\u00e8ne, <span style=\"color: #ff0000;\">A<sub>1<\/sub>&#8216;<\/span> le point o\u00f9 est entendu le premier \u00e9cho, <span style=\"color: #ff0000;\">A<sub>2<\/sub>&#8216;<\/span> le point o\u00f9 est entendu le deuxi\u00e8me \u00e9cho.) kamerpower.com<\/span><\/li>\n<li style=\"text-align: justify;\"><span style=\"color: #000000;\">Sachant que l\u2019appareil <a style=\"color: #000000;\" href=\"https:\/\/kamerpower.com\/\" target=\"_blank\">auditif<\/a> humain est incapable de distinguer deux sons successifs lui parvenant dans un intervalle de temps <span style=\"color: #ff0000;\">dT<\/span> inf\u00e9rieur \u00e0 <span style=\"color: #ff0000;\">0,1 s<\/span>, quelle est la distance minimale <span style=\"color: #ff0000;\">d<\/span> au dessus de laquelle on n\u2019entend plus d\u2019\u00e9cho?<\/span><\/li>\n<\/ol>\n<hr \/>\n<p>&nbsp;<\/p>\n<h3 style=\"text-align: center;\"><span class=\"ez-toc-section\" id=\"kamerpower-probleme-2\"><\/span><span style=\"color: #3366ff;\">Kamerpower Probl\u00e8me\u00a02<\/span><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\"><span style=\"color: #000000;\">Le <span style=\"color: #ff0000;\">pH<\/span> d\u2019une solution aqueuse d\u2019acide formique <span style=\"color: #ff0000;\">HCOOH<\/span> de concentration <span style=\"color: #ff0000;\">Co=2.10<sup>-2<\/sup> mol l<\/span><sup><span style=\"color: #ff0000;\">-1<\/span>\u00a0<\/sup>est \u00e9gal \u00e0 <span style=\"color: #ff0000;\">2,7<\/span>.<\/span><\/p>\n<ol style=\"text-align: justify;\">\n<li><span style=\"color: #000000;\">\u00a0Calculez la valeur du <span style=\"color: #ff0000;\">pKa<\/span> de cet acide.<\/span><\/li>\n<li><span style=\"color: #000000;\">\u00a0Combien de moles de formiate de sodium <span style=\"color: #ff0000;\">HCOONa<\/span> doit-on ajouter \u00e0 <span style=\"color: #ff0000;\">500 ml<\/span> de la solution initiale pour obtenir une solution de tampon de <span style=\"color: #ff0000;\">pH=3,7<\/span>\u00a0?<\/span><\/li>\n<li><span style=\"color: #000000;\">Combien de moles de soude doit-on ajouter \u00e0 la solution tampon de <span style=\"color: #ff0000;\">pH=3,7<\/span> pour obtenir une solution de formiate de sodium\u00a0? Quel est le <span style=\"color: #ff0000;\">pH<\/span> de cette solution\u00a0? kamerpower.com<\/span><\/li>\n<li><span style=\"color: #000000;\">Tracez la courbe de neutralisation de l\u2019acide formique par la soude.<\/span><\/li>\n<\/ol>\n<p style=\"text-align: justify;\"><span style=\"color: #000000;\"><span style=\"text-decoration: underline;\">N.B<\/span>\u00a0: On admettra que l\u2019addition des r\u00e9actifs n\u2019entra\u00eene pas de variation de volume.\u00a0On prendra <span style=\"color: #ff0000;\">log 2 = 0,3<\/span>.<\/span><\/p>\n<p style=\"text-align: justify;\"><span style=\"color: #ff0000;\">On utilisera les relations approch\u00e9es\u00a0:<\/span><br \/>\n<span style=\"color: #000000;\">Acide faible en solution (concentration molaire C)\u00a0:<span style=\"color: #ff0000;\"> pH=0,5. (pKa \u2013 log C)\u00a0;<\/span><\/span><br \/>\n<span style=\"color: #000000;\">\u00a0Sel d\u2019acide faible et de base forte en solution (concentration molaire C <strong>&#8216;<\/strong> )\u00a0:<\/span><br \/>\n<span style=\"color: #ff0000;\">pH = 7 + 0,5. (pKa + log C <strong>&#8216;<\/strong> ).<\/span><\/p>\n<h2 style=\"text-align: center;\"><span class=\"ez-toc-section\" id=\"epreuve-concours-ensp-physique-et-chimie-cameroun-1-concours-dentree-a-lecole-nationale-superieure-polytechnique\"><\/span><span style=\"color: #3366ff;\">Epreuve Concours ENSP Physique et Chimie Cameroun 1 concours d&#8217;entr\u00e9e \u00e0 l\u2019Ecole Nationale Sup\u00e9rieure Polytechnique<\/span><span class=\"ez-toc-section-end\"><\/span><\/h2>\n","protected":false},"excerpt":{"rendered":"<p>&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":5914,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_themeisle_gutenberg_block_has_review":false,"footnotes":""},"categories":[1701],"tags":[1724,1712,1727,1726],"class_list":["post-6827","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-epreuves","tag-chimie","tag-epreuve-de-concours-dentree-aux-grandes-ecoles-cameroun","tag-epreuve-ensp-concours-cameroun","tag-physique"],"_links":{"self":[{"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/posts\/6827","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/comments?post=6827"}],"version-history":[{"count":0,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/posts\/6827\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/media\/5914"}],"wp:attachment":[{"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/media?parent=6827"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/categories?post=6827"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kamerpower.com\/fr\/wp-json\/wp\/v2\/tags?post=6827"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}